Art. XXIV.—The Leaf-mining Insects of New Zealand: Part II.
[Read before the Wanganui Philosophical Society, 24th October, 1920; received by Editor, 31st December, 1920; issued separately, 20th July, 1921.]
This genus is represented in New Zealand by the following eight species, four of which are dealt with in the present paper; it is probable that a number still remain to be found:—
- Nepticula ogygia Meyr., Trans. N.Z. Inst., vol. 21, p. 187, 1889.
- — tricentra Meyr., Trans. N.Z. Inst., vol. 21, p. 187, 1889.
- — propalaea Meyr., Trans. N.Z. Inst., vol. 21, p. 187, 1889.
- — cypracma Meyr., Trans. N.Z. Inst., vol. 48, p. 419, 1916.
- — oriastra Meyr., Trans. N.Z. Inst., vol. 49, p. 247, 1917.
- — lucida Philp., Trans. N.Z. Inst., vol. 51, p. 225, 1919.
- — perissopa Meyr., Trans. N.Z. Inst., vol. 51, p. 354, 1919
- — fulva n. sp., herein, p. 215.
Main Characteristics of Genus.
The main characteristics of the genus are as follows:—
Head hairy, tufted; tongue rudimentary; antennae with basal joint enlarged to form an eye-cap; maxillary palpi rather long, folded; labial palpi short, slightly porrected. Forewings rather broad, short. and coarse scales, the termen clothed with long cilia and shorter scales, these latter may be darker at their tips and so form one or more, more or less distinct “cilial lines.” Hindwings lanceolate; frenulum multiple in both sexes.
Within the genus there are two types of venation in the forewing. In the more primitive one the media coalesces with the cubitus for a short distance from the base, then passes obliquely to the radius just beyond R2 + 3, and anastomoses with the radius to beyond the middle of the wing. In the second type the media coalesces with the ladius from the base to beyond the middle of the wing. All four species dealt with in this paper belong to this latter type. Forewing: Costal vein (C) small and insignificant, there is no costal trachea in the pupal wing except in the more primitive type, where it is extremely short; subcostal (Sc) in the more primitive type is connected to the costal near the base by a short oblique humeral cross-vein (h), the pupal trachea is distinct and in the latter type is branched near its tip; radius represented by three veins, R1 and R2 + 3 running parallel to each other to costa, the third, R4 + 5, to apex, bifurcated in the primitive type; media represented by an unbranched vein (M1) reaching the wing-margin below the apex; cubitus (Cu1b), unbranched, and becomes
Fig. 1a.—Pupal forewing of the more primitive type of Nepticula. The wavy lines represent the tracheae, the dotted lines represent the veins that are found later.
Fig. 1b.—Pupal forewing of N. tricentra about one week before emergence.
Fig. 1c.—Pupal hindwing of N. tricentia about one week before emergence
obsolete at or before the middle of the wing; anal veins, 1A present, extending almost whole length of dorsum, 3A sometimes present in the more primitive type but extremely short. Hindwing: Costal vein (C) as in forewing, but there is no trachea to be found in the pupal wing; sub-costa (Sc)—this contains both its own trachea and that of R1; radius, in the pupal wing R1 leaves the mam stem near the base to become incorporated in the same vein-cavity as the subcostal, while the remainder of the radial sector is reduced to a single unbranched trachea (R5) lying in its proximal half, in the same vein-cavity with the medial trachea; media, a single unbranched vein (M1) to below apex; cubitus (Cu1b), a single unbranched vein extending to dorsal wing-margin at or beyond ½; anal veins one, 2A; in some species 3A may be present but is extremely short and has no trachea in the pupal wing.
Libera, with segments and appendages free. Maxillary palpi exceedingly well developed, emerge from beneath the antennae and turn inwards forming the eye-collar which contains only the terminal joints, the others are concealed deeply; on dehiscence remain attached to the head-parts. The body is oval in outline, about one and a half times as long as broad, and slightly flattened dorso-ventrally. The mesothoracic spiracle is in the primitive position ventral to the caudo-lateral angles of the prothorax; the spiracles of the first abdominal segment are uncovered by the wings. Setae absent. Epicranial and fronto-clypeal sutures always present, though not conspicuous. Appendages freehand segmented, and separate readily on slight violence; the thoracic appendages are widely separated to show all the coxae. Pupa in a cocoon; partly protrudes from cocoon before emergence of the imago; cast larval skin within the cocoon and frequently attached to the caudal extremity of the pupa. Tutt says (Nat. Hist. of the British Lepidoptera, vol. 1, p. 180), “the antenna-cases on dehiscence divide into the cover of the first and that of the remainder, each separate from the head, yet still held together sufficiently to keep their places fairly.”
Head small, flattened; the front is narrowed caudad, the lobes of the epicranium extend caudad to a considerable distance behind the meeting-point of the front and vertical triangle, there is a single large and conspicuous ocellus on each side. Body when full-grown cylindrical, attenuated caudad, segmental incisions well defined; prothorax tumid; no true legs, but eight pairs of membranous prolegs without hooklets (some species without prolegs), two pairs on thorax and six on abdomen; dermis transparent. Mines in leaves, and lives on the parenchyma.
Large for the size of the moth; flat and scale-like; roundish oval in outline; micropyle at one end. Laid singly and attached to food-plant.
Chief Characteristics in Each Stage.
The chief characteristics to be noted in each stage of the life-history as an aid to the identification of the species:—
The Imago.—(1) Colour of head, basal joint of antenna, and prothoracic collar; (2) colour and markings of wings and cilia, and presence of cilial lines; (3) colour of thorax, abdomen, and legs.
The Ovum.—(1) Where situated, whether any particular portion of the leaf or stem is favoured more than any other part; (2) size, colour, and sculpture.
The Larva.—(1) General colour of body during early stages and when full-grown; (2) the colour and shape of the head; (3) markings on the prothorax, visibility of cephalic ganglia and prothoracic shield; (4) colour and appearance of ventral nerve-chain; (5) colour of intestinal canal; (6) dorsal marks on last three abdominal segments; (7) saetal plan.
The Mine.—(1) The food-plant; (2) situation on stem or leaf, whether in upper or lower surface; (3) in what particular part of the leaf; (4) its course—straight, tortuous, or vermiform; (5) whether a simple gallery, blotch, or combination of both; (6) discoloration of surrounding leaf-substance; (7) the deposition of the frass—granular, lumpy or fluid, fine or coarse, colour, copious or scanty, how deposited in the mine.
The Cocoon.—(1) Situation, whether within the mine or without; (2) size, shape, and colour.
The Pupa.—(1) The relative lengths of the thoracic appendages; (2) the arrangement of the dorsal abdominal spines; (3) the relative lengths of the coxae; (4) relative size.
(9.) Nepticula ogygia Meyr. (The Olearia Gallery-Nepticulid).
Nepticula ogygia Meyr., Trans. N.Z. Inst., vol. 21, p. 187, 1889; vol. 47, p. 231, 1915.
Meyrick's Original Description—“♂. 7 mm. Head and palpi pale whitish-ochreous. Antennae grey. Thorax and abdomen grey, sprinkled with ochreous-whitish. Legs dark grey, apex of joints whitish. Forewings lanceolate; pale grey, coarsely irrorated with black; an obscure cloudy ochreous-whitish suffusion towards costa at ⅔; an obscurely-indicated pale spot in disc before middle: cilia whitish-ochreous-grey, with an obscure line of dark scales round apex. Hindwings and cilia light grey.”
The above description was taken from a single specimen, most possibly caught in the field. During the last few seasons I have been fortunate in rearing a good series of this rather rare little moth. There is a slight degree of variation in some of the specimens, principally in the amount of dark irroration in the forewing, which in some specimens is quite scanty, and the moth appears to the naked eye as light grey instead of black. The following description is taken from freshly emerged specimens:—
Head and palpi pale yellowish-ochreous, collar and basal joint of antenna whitish. Antennae pale grey, under 1, about ½. Thorax grey, densely irrorated with black. Legs and abdomen light grey. Forewings pale grey, thickly irrorated with black scales; a small pale area on dorsum near tornus (this appears to be the most constant marking, and is quite conspicuous when the wings are folded at rest, when the two areas form a small saddle-shaped spot on the dorsum); in the female there is a second similar area on costa, and frequently the two may form an obscure light band across the wing; a very diffuse pale spot in disc at ¼, frequently absent; a series of four small black spots in middle of wing, one at ¼, ⅓, ½, and the fourth less distinct near termen; these spots are definitely fixed as to position, but one or more or all may be absent, that at ½ being the most constant: cilia pale grey with bluish reflections, a distinct black cilial line. Hindwings dark grey; cilia dark grey.
The imago of this moth is not very common in the field, though its mines may be found in large numbers on the food-plants. This may be accounted for by the fact that it rarely flies except in bright sunshine, the slightest dullness sending it to cover amongst dead vegetation, and in crannies in the bark of the food-plant, from which it requires fairly rough treatment to dislodge it, and even then will prefer to run to a new hiding-place rather than take to the wing. At rest its coloration is very protective, and in consequence it is a most inconspicuous object. In the sunshine its movements are quick and restless, and it rarely ventures far from its food-plant.
Meyrick records the [original specimen from Dunedin in January: I have found it there during the last few seasons. Typical mines, but empty, were found at Dawson's Falls, Mount Egmont, in December, of 1917, in Olearia Cunninghamii (?). Not being in Dunedin during the latter half of December and the first two months of the year, I have been unable to record the activities of this moth during these months. My first observations are dated July, 1919, when I obtained full-grown larvae, these pupating during the early part of the month, and beginning to emerge at the end of the first week of September. Larvae and cocoons were again obtained in July, 1920. In September of both years imagines were found, and many ova; a few larvae were found early in the month in 1919, these pupating in the second week and emerging during the first week of November, while numbers of larvae were pupating towards the middle of September, 1920, emerging towards the end of October. A number of imagines were obtained about the middle of November. There are therefore probably four, if not five, generations a year, but there is a fair amount of overlapping. Imagos may be looked for towards the end of June, early September, the end of October, and throughout November, and in January and possibly March. It is probable that hibernation takes place in the cocoon.
Olearia nitida (now O. arborescens and O. divaricata) and O. macrodonta, the former apparently being the favourite. Chiefly around the margin of the bush. At Mount Egmont in O. Cunninghamii (?).
The Ovum and Egg-laying.
The Ovum.—Oval, wafer-like, flattened against the leaf where it is attached, rounded above. Micropylar end slightly broader than its nadir. Around the outer margin of the egg the shell is slightly produced so as to form a flattened foot or fringe closely applied to the surface of the leaf. This fringe is a slight degree wider at the micropylar end of the egg. A large number of eggs were measured, and their dimensions varied but little; in the fresh state this is the easiest way to distinguish the egg from that of N. fulva, which is larger. Average length of fresh egg, including fringe, 0–42 mm.; average transverse diameter, 0–30 mm.; average height, 0–12 mm. Empty shells are smaller than the above, and without including the fringe, which is inconspicuous, the average length and breadth is 0–40 mm. by 0–29 mm. There is a slight roughening of the shell, but otherwise no definite sculpture or reticulation. The micropyle is situated at the broader end of the egg, but its structure was not observed. The shell is only very slightly roughened; shiny, strong, transparent. The colour is bright blue when first laid. As the embryo develops,
the blue colour becomes replaced by yellowish, especially at one end. Later the white embryo can easily be seen within the shell. After hatching, the shell becomes filled with particles of white frass. The egg is easily found, and the empty shell, which is strongly attached to the leaf, persists long after the larva has left the mine and pupated, the shiny white shells being quite conspicuous at the commencement of the galleries.
Egg-laying.—This naturally takes place during those months in which the imagos are to be found (see above). The ova are deposited singly, invariably on the upper side of the leaf with the one exception of the August-September brood mentioned below. The most favoured position for the egg is alongside the midrib of the leaf, and the locality next in favour is alongside one of the coarser veins or ribs. A number of eggs may be found on any one leaf, but it is likely that these have been deposited by. several females. It has been noticed that in such cases the majority of the eggs were laid on the basal half of the leaf. When the August-September eggs are being laid the food-plant, O. nitida, is sending out its fresh spring buds, and on the hairy outer side (what will later be the underside) of the bud leaves many of the ova of this moth are attached, with peculiar consequences, as will be seen.
The Mine. (Plate XL.)
The mine is a narrow, usually more or less tortuous gallery, constructed entirely under the upper cuticle of the leaf. The larva burrows directly through the bottom of the egg into the leaf-substance; and following this there is no purple discoloration of the leaf in the egg area such as there is in the case of N.fulva on the same food-plants. The gallery is not a long one, its average length ranging from 4 cm. to 6 cm.; its course follows the coarser ribs of the leaf, these and the midrib forming a bar to progress across them. For this reason, and on account of the ova being usually
deposited alongside the midrib of the leaf, most of the mines will be found to be within the primary loops formed by the veins–i.e., those nearest, the centre of the leaf. Towards the outer margin of the leaf neither the midrib nor the coarser veins form very serious obstacles, and may be crossed by the mines. The width of the mine increases very gradually, and at its terminal portion is not more than 1–5 mm. The frass (sec Plate XL) is-black and coarsely granular, abundant, and occupies an almost unbroken chain along the middle half or three-quarters of the gallery; it is entirely absent in the terminal half-centimetre of the mine; it is
deposited against, and remains attached to, the roof of the mine. Individual leaves of O. nitida may contain many mines, but these never interfere with one another, and, however cramped the room at disposal, a gallery will seldom ever cross itself, tending rather to become closely vermiform, with its loops applied to, but not encroaching upon, each other. I have rarely found more than three or four mines in any one leaf of O. macrodonta; and frequently the mines on this plant cause the leaf-tissue in their immediate vicinity to become discoloured with a reddish tinge. The length of time occupied in constructing the mine is short—two or three weeks in all. I have several times noted ova, and on returning some three weeks later have found nothing but empty mines The colour of the mine is light brown, and the black frass under the thin transparent cuticle causes it to become very conspicuous. On holding the leaf up to the light the mine is a pretty and striking object. When full-fed the larva emerges through a semicircular cut in the roof of the gallery at its terminal part, and makes its way to the ground. There remains a curious fact to be noted.: In the case where the ova are laid on the leaf-buds of O. nitida it is not the upper surface of the leaf to which they are attached, this surface being snugly tucked away in the interior of the bud; it is to what will become the under-surface of the leaf, and amongst the thick covering of hairs that protect it at this time, that the ova are firmly cemented. No matter whether it be the upper or lower surface to which the egg is attached, the mine is always constructed close against the actual upper surface. The midrib here, even in these small succulent leaves, prevents, in all but a few cases, the larva from mining from one half of the leaf to the other; the consequence is the mine becomes closely looped backwards and forwards in the direction of the long axis of the growing leaf, so as to fill almost completely one half of the leaf. In this looped, vermiform fashion the mine has progressed from the margin of the leaf towards the centre, as though the larva were aware that any other mode of tunnelling would cut off the sap-supply and leave it short of food. The mine usually progresses in a looped, vermiform fashion, from the margin of the leaf to the centre; but in very young leaves it often happens that when the thin half has been destroyed the tunnel actually enters the midrib. The course then taken is always downwards, the point of emergence lying 1 in. or less below the base of the leaf.
It is rare to find more than one larva mining in any one of these young leaves. These mines have a curious effect upon the subsequent growth and shape of the leaves. Practically one half of the leaf has been destroyed, but the other half has all the time had its sap-supply (even when the larva was in the stem, for the mine is very small, probably one-third of the transverse diameter of the stem), and has grown accordingly; the result of one half of the leaf growing and the other not has been to cause it to become curled around the axis. During November a large number of these curled leaves are to be found on the food-plant. Except in the very young leaves there is little of the mine to be seen on the under-surfaces; in the older leaves there may be a slight darkening of the colour along the track of the mine, and also the surface may be slightly elevated. The entire mine is in the spongy parenchyma of the leaf and leaf-stem.
Length when full-grown, about 4 mm. The ground-colour is very pale green, with a comparatively broad dark-green central line (intestinal canal
containing food) commencing in the first abdominal segment, to the end of 6. A narrow dorso-lateral line on the last segment. Most of the internal organs can be distinguished. Headpiece pale amber-brown, darker round external margins, clypeal sutures, and mouth-parts. Head almost wholly retracted into the prothorax. No true legs or prolegs, but protrusible fleshy enlargements on the ventral surface of segments 2, 3, 4, 5, 6, 7, and on the mesothorax and metathorax. The larva is cylindrical, slightly flattened dorso-ventrally. The mesothorax has the greatest diameter, then the metathorax and segments 1 to 7, which are about equal; 8, 9, 10 attenuated; segment 9 about the shortest in the body; segments not deeply incised but evenly rounded. Ventral chain of fairly large somewhat elongated grey diamond-shaped ganglia, quite distinct with double connecting bands, the thoracic ganglia larger and more elongated than the abdominal ones. Cephalic ganglia dark grey, easily distinguished as backward extensions of the head-capsule into the prothorax, and when the head is retracted extend into the mesothorax and are not so easily distinguished. Head flattened, bluntly triangular. Skin covered with a fine pile; tubercles and setae present, setae comparatively long, the longer ones being about two-thirds the length of their respective segments. The details of the setal plan are left for a future paper. The colour of the larva when it leaves the mine is pale yellow throughout. The larva mines dorsum uppermost. It can easily be seen in the mine by holding the leaf up against the light. The frass-track ends abruptly, and the remainder of the mine is filled by the light-coloured larva, its dark central line making it at once conspicuous. Even under ordinary circumstances a practised eye can tell at once whether a mine is inhabited, or not, by the nature of its wider extremity; in the empty mine this end is very light in colour and in strong contrast to the remainder of the gallery, is devoid of frass, and contains the conspicuous semicircular outlet cut by the escaped larva. In inhabited mines the wider extremity is lighter in colour than the rest owing to the absence of frass, the narrow dark central line of the larva taking the place of this latter; but most characteristic of all is the slightly domed roof of this portion of the mine, caused by the larva within. The colour of this part of the mine is a somewhat paler green than the rest of the leaf-surface, whereas in the empty mine it is yellowish or light brown, light grey, or very pale green, according to the length of time since it was vacated.
Somewhat ovate, mussel-shaped, ends rounded, anterior end slightly flattened and broader than its nadir. The outlet of the cocoon is guarded by a pair of flattened closely-applied lips extending across the whole front of the cocoon. Length averaging 3 mm., width 2–2.5 mm., height 1–1.5 mm. Colour at first whitish, changing to light green, to dark brown; occasionally the cocoons retain their green colour throughout. Interior of cocoon whitish. Texture thin but dense, forming a kind of skin, and surrounded outside, except where attached to external objects, by a small amount of light floccy silk. Situated amongst dead herbage on the ground in the neighbourhood of the food-plant. Two days are usually occupied in the construction of the cocoon. After the last larval moult the cast skin remains attached to the caudal end of the pupa; in many other genera it is extruded from the cocoon. Pupal period, of course, depends on local climatic conditions. A number of specimens pupated 1st July, 1919, and emerged 8th September, 1919—seventy days; another batch pupated 15th September,
1920, and emerged 24th October, 1920—thirty-nine days. It is possible that the larva hibernates in the cocoon.
Female.—Ventral view : In outline the front is rounded and bluntly prominent; laterally there is a small incisura between it and the base of the antenna; this latter occupies the lateral outline for only a very short distance. The upper half of the lateral outline is evenly curved convex, and is formed by the forewing; the lower half is also curved convex but is interrupted by the depression between each segment, it is occupied by segments 3 to 10 inclusive; a small amount of the prominent spiracles appears on the lateral aspect of each segment, those on the eighth being especially prominent. The last abdominal segment is bluntly rounded and is slightly notched caudad; the genital opening can be detected on its ventral surface. Only a little of the eye is freely exposed, its upper third being covered by the base of the antenna, and its lower third by the maxillary palpus. The maxillary palpus is well developed, its expanded base resting against the antenna, and its bluntly pointed mesial extremity touching the labrum. This latter broad and rounded. Labial palpi narrow, and reach just below the lower extremities of the maxillae. The maxilla is broad above, its base resting against the mesial half of the maxillary palpus and portion of the labrum between it and the labial palpi; its caudal extremity does not reach quite so far as that of the labial palpus. First legs broad and short, reaching from the maxillary palpus above to about half-way between the caudal extremities of the first and second coxae; a slight slip of the femur is interposed in the upper third between the base of the leg and the maxilla; appearing as a short extension caudad is the tibia of the second leg, reaching to the caudal extremity of the second coxa. Second legs narrow in their upper third, and occupy a position between the antennae laterally and the first legs, second tibiae and second coxae mesially; at their upper extremity they rest against the maxillary palpus and become fairly broad about their middle, extending caudad to about the middle of the fourth abdominal segment, which is here exposed; appearing from beneath the extremity of the second leg is a short process, the tibia of the third leg. Third legs appear from beneath the forewings in the angle between them and the third tibiae; they soon meet in the mid-line and extend to the upper border of the last abdominal segment. Antenna narrow, plainly segmented, lies close against but terminates slightly higher than the second leg. The coxae of all three legs are broad and of about equal length. Between the third coxae above and the third legs below a small area of the ventral surface of the third, fourth, and fifth abdominal, segments can be seen. It is here and about the eyes and labrum that the first colour-changes take place. Forewing somewhat narrow, terminates caudad in a fairly acute point on a level with the caudal extremities of the third legs. In some specimens a very slight slip of the hindwings appears at the caudal extremity of the forewing, between it and the third leg.
Dorsally : The prothorax is a very narrow strip; the mesothorax and metathorax fairly large; only a small portion of the hindwings is exposed; spiracles on all the abdominal segments 1 to 8 inclusive, and situated on prominent elevations, the greatest being on the second segment; segments 3, 4, 5, 6, 7, bear a single row of small stout brown spines near their upper margin, this line is interrupted in the centre by the medio-dorsal ridge and extends laterad to within a short distance of the spiracular elevation; segment 10 bears a pair of fairly prominent upcurved hooklets, dark brown in colour. The surface of the abdominal segments is slightly roughened dorsally by a minute pile when viewed with a ½ in. objective. Head-sutures not very distinct. A slightly elevated medio-dorsal ridge extends from the eighth segment to the prothorax. Free movement between all the abdominal segments except the two caudal ones.
Laterally the head is situated somewhat ventrad. The ventral outline is slightly convex, almost straight. Dorsal profile well rounded; mesothorax slightly prominent anteriorly; first abdominal segment somewhat sunken; abdomen well rounded; spiracular eminences very prominent, in descending order of magnitude from above down, the second being the largest. The two upturned hooks on segment 10 conspicuous. Forewing occupies about one-third of the whole lateral body-surface. Head and thoracic appendages occupy the cephalo-frontal third, the abdomen the caudo-dorsal third. Colour at first pale green, later changing to dark grey.
Male.—The abdominal segments 3, 4, 5, 6, 7, and 8 bear the dorsal row of spines; the antennae are slightly longer than the second legs, and the forewings slightly longer than the third legs, these latter extending as far as the caudal extremity of the last segment. The chief sexual differences are the presence of the dorsal spines on segment 8 and the greater length of the antennae.
|Measurement at||Length from Extreme Front.||Transverse Diameter.||Ventro-dorsal Diameter.|
|Upper border of maxillary palpi||0.28||0.69||0.52|
|Bottom of labial palpi||0.55||0.96||0.69|
|Bottom of first legs||0.89||1.00||0.71|
|Bottom of second legs||1.44||0.93||0.83|
|Bottom of third legs||2.17||0.41||0.38|
The pupa is extruded from the cocoon to a level a little below the end of the second legs. Splitting takes place vertically on the dorsum along the mid-dorsal ridge of the vertex, prothorax, and mesothorax, and transversely along the epicranial suture as far laterad as the antennae. Cephalad the basal joint and rest of the antennae become detached in one piece, but this remains attached to the narrow strip of the vertex which keeps it from becoming displaced and lost; the antenna usually remains more or less attached to the other appendages caudad. The headpiece remains attached ventrad to the mandibles and other structures.
After emerging the moth usually rests upon some horizontal surface while the wings attain their full length; this accomplished, they are thrown perpendicularly over the back, their dorsal surfaces in contact, and remain
thus for ten to fifteen minutes, after which they are dropped to their normal position and the imago becomes active. The imagines emerge in the daytime.
(10.) Nepticula perissopa Meyr. (The Rangiora Nepticulid).
Nepticula perissopa Meyr., Trans.N.Z. Inst., vol. 51, p. 354, 1919.
Meyrick's Original Description.—♂♀. 6–7 mm. Head and eye-caps whitish-ochreous, centre of crown dark grey or blackish. Thorax dark violet-fuscous. Abdomen grey. Forewings broad-lanceolate; pale greyishochreous, more or less suffused (especially in ♂) with violet-grey, and coarsely and irregularly strewn with dark-fuscous scales, especially towards apex, where in ♀ they form a suffused dark blotch occupying ¼ of wing; an elongate dark-fuscous spot on fold at ¼; an elongate blackish spot in disc beyond middle, in ♀, surrounded by a nearly clear space: cilia pale greyish-ochreous, basal ⅔ coarsely irrorated with blackish round apex and upper part of termen. Hindwings grey : cilia light ochreous-grey.”
General Description.—Female. 6–8 mm. Head light yellowish-brown; base of antennae whitish, antennae about ½, dark grey. Thorax and abdomen dark grey to black. Forewings broad, ground-colour whitish with a paleviolet reflection in a bright light, irrorated with black scales; at about ⅔ the whitish scales predominate slightly so as to form a fairly broad and sometimes quite distinct pale transverse bar across wing; the black scales predominate in the terminal ¼ of the wing, and near the apex surround a distinct round spot, black in some lights, golden-brown in others; a similar but smaller spot in centre of wing a little beyond ½, the light transverse bar before mentioned separating the one from the other. In some specimens there may be slight evidence of a second light transverse bar across wing to the inner side of the central spot. A black cilial line; cilia dark grey with violet and reddish reflections.
In the male the black scales greatly predominate, and there is little or no evidence of light transverse bars. The central spot is sometimes missing.
Two specimens were caught by Mr. Hudson on Mount Egmont in February. It was here also that I first found mines with larvae and pupae—at Dawson's Falls, 23rd December, 1917, at an elevation of 2,500 ft. I have also found it since in the Botanical Gardens in Wellington, where it is fairly common. I noted the following dates: 19th June, 1919, larvae and cocoons found; 20th September, 1919, larvae, cocoons, and one imago; first week of October, 1919 and 1920, larvae, pupae, and imagines found. There are probably three broods. Old mines have been found both at Aberfeldy and at Long Acre, in the Wanganui district.
Brachyglottis repanda (rangiora).
I have not yet seen the egg in the fresh state; the following description is taken from a number of empty shells persisting at the commencement of the mines :—
Class: Flat (?). Shape: Wafer-like, oval, slightly broader at the anterior end, domed above. Dimensions : Length, 0–51 mm.; transverse
diameter, 0–38 mm. Sculpture : Nil. Micropyle : Not observed. Shell : Shiny, smooth, transparent, strong; is firmly cemented to the leaf, and persists at the commencement of the mine for many weeks filled with frass. Colour: The empty shell appears white and shiny, and is easily found.
The ova are laid singly, and there are rarely more than one or two to a single leaf. In all the cases I have come across the egg is attached to the upper surface of the leaf, and with a marked preference for a situation in the vicinity of the midrib or one of the coarser veins. I have noticed that in the great majority of the species of leaf-miners which construct fairly long galleries there is a preference for this site near the midrib or one of the coarser veins, and the larva almost invariably commences to mine along this boundary towards the outer margin of the leaf, in the region of which the greater part of the mine will be constructed. In cases where the egg is laid in more open spaces on the leaf there is no such immediate choice of direction towards the outer margin, but once the larva reaches either the midrib or one of the coarser side veins it will mine along it until it reaches the outer portions of the leaf. The advantages of mining in the outer parts are obvious; but if the eggs are deposited with a definite idea it is puzzling to account for their not being laid near the outer margin of the leaf in the first place. It appears that it is really immaterial where the egg is laid, as the larvae do not seem to suffer any inconvenience through the egg not being attached to one or other of the ribs; one is therefore led to believe that the choice of any particular part of the leaf is not made out of consideration for the future larva.
The Mine. (Plate XLI, figs. 1, 2.)
The mine is a long narrow gallery terminating in an expanded blotch, and is constructed immediately beneath the upper cuticle of the leaf. Its general direction is, as a rule, from within towards the margin of the leaf. The gallery portion in its earlier part has a beaded appearance when viewed under a low power, owing to the actual width of the mine being somewhat
smaller than the diameter of the cells through which it passes; all the leaf-substance within the cell is eaten, and so the margin of the mine is slightly scalloped in appearance. This early part of the mine is, as a rule, far less tortuous than the later portions. The latter two-thirds of the gallery is frequently very tortuous, and it may at times even cross the
midrib of the leaf, usually an effectual barrier except in its upper sixth. Occasionally in large leaves the course of the gallery will be but little deflected. The gallery may average 6 in. in total length. I have found that the Wellington mines are as a general rule much larger and less tortuous than the Egmont ones, which are frequently so tortuous as to be almost confined to about a square inch of the leaf-surface exclusive of the blotch; in such cases the leaf-substance between the convolutions of the gallery soon becomes dead and of the same colour as the gallery, and so simulates a blotch which may be separate from or coextensive with the actual blotch. The blotch is irregular in shape, its margin fairly even, and may average ¾ square inch in area; its construction occupies about a week.
Frass is plentiful, finely granular, black, and in the gallery is deposited in the central three-fourths of the mine; a tendency is sometimes seen for the frass to be deposited in a double row, but this is infrequent and generally not very marked. In the blotch the frass is found chiefly in the earlier portion, and is arranged in rows or shallow loops, convex forwards, across the mine in the track taken by the larva. The last act of the larva is to prepare an outlet at the margin of the blotch, and just within this it constructs its cocoon.
The early part of the gallery frequently follows the midrib, margin, or one of the coarser veins of the leaf, but these latter do not form very serious barriers to the young larvae. The width of the gallery, though irregular, increases gradually till it suddenly expands into the blotch. The average width would be about 1 mm. The blotch is frequently against the margin of the leaf, and always includes a small portion, ½ in. or so, of the terminal portion of the gallery. The midrib and veins are more effectual barriers to the blotch than they are to the gallery. Colour of the mine in the freshest portion pale green, but the cuticle rapidly becomes dead and brown over the roof of the mine. Frequently irregular portions of the gallery become reddish-brown, but the darkest discoloration is in the immediate neighbourhood of the ovum and the first 1 mm. or 2 mm. of the mine. The blotch becomes brown very rapidly, even while the larva is at work. The mine becomes very conspicuous in consequence of these colour-changes. In the blotch, before the cuticle dies, the frass rows are clearly discernible. The frass is deposited against the upper cuticle, to which it adheres; sometimes in the gallery it may occupy a narrow, more or less uninterrupted central line.
On the underside of the leaf the mine can hardly be seen, its presence being sometimes made known by a slight swelling of the under-surface along its course. Beneath the blotch, however, the under-cuticle becomes loose and wrinkled, and loses its slightly roughened appearance.
When young the larva is white in colour, flattened, moniliform; alimentary canal greyish-brown. In the fully-fed larva the body is cylindrical, only very slightly flattened dorso-ventrally; length about 5 mm.; head flattened, retractile, rounded, in the younger larvae bluntly triangular; segments well rounded but not deeply incised, the mesothorax has the greatest diameter, the metathorax and first seven abdominal segments being about equal, segments 8 to 10 acutely attenuated; there is a deep constriction between 8 and 9; 9 is very small. Ground-colour palest green, almost white; central marking fairly broad, light yellow from the head to the
eighth abdominal segment; head pale yellowish-brown, sutures and mouthparts reddish and darker. Cephalic ganglia not noticeable; ventral chain not noticeable; no conspicuous markings; the thin brown lateral lines on the dorsum of the last segment are situated so far laterally as to be almost out of sight when the larva is viewed dorsally. Surface of body covered with a very minute pile. Setae inconspicuous; main setae about half as long as their respective segments. The larva mines dorsum uppermost. It is a frequent prey to minute hymenopterous parasites, the pupal duration of which is about fifteen days.
The cocoon is constructed within the blotch close against its outer margin, where the larva, previous to the construction of the cocoon, cut a slit-like opening through the lower cuticle; this slit may be 4 mm. to 5 mm. in length, but is very inconspicuous. The presence of the cocoon is made known by this slit and by a slight bulging of the under-cuticle where it is situated. It is rarely noticeable from above, though sometimes the cuticle covering it may become slightly lighter in shade where the cocoon is attached. The cocoon can easily be found by holding the mine against the light. It is attached to both the roof and the floor of the mine, but more firmly to this latter, from which it is almost impossible to detach it completely. When seen against the light the anterior third is lighter in colour than the rest, as the pupa is situated farther back and the structure of the cocoon is here somewhat less dense. At the anterior end of the cocoon its floor and roof can easily be split apart; this is the prepared outlet for the pupa. The cocoon is oval in shape, broader at its anterior end, 4–5 mm. by 2 mm., flattened top and bottom 1 mm. The silk on the outside is pale-yellowish and compact, and within this is an inner cocoon of white silk which also has its prepared anterior outlet. When the imago is ready to emerge the pupa is thrust out the anterior end of the cocoon and through the slit in the under-cuticle, the anal segments being retained within the cocoon. The presence or absence of the empty puparium indicates the state of affairs within the cocoon. Emergence takes place on the under-surface of the leaf.
Ventral view : Outline oval; front bluntly rounded; a slight incisura between front and base of antenna, this latter slightly prominent The last six abdominal segments occupy the lower third of the lateral profile. Spiracles prominent, especially on 8. Last segment rounded with a slight caudal notch; genital opening showing on the ventral surface. The eye is covered over its cephalo-lateral third by the base of the antenna, and slightly caudad by the maxillary palpus. Fronto-clypeal suture not very distinct. Maxillary palpus well developed; reaching from the antenna laterad to the labrum, of which it sometimes falls slightly short; broadest at its base against the antenna. Labial palpi narrow, slightly bulbous in their caudal half; extend caudad farther than the maxillae. Maxilla broad cephalad; occupies the mesial half of the maxillary palpus; pointed caudad. First legs fairly short and stout, broader cephalad; extend to just below the first coxae; the femur occupies a small narrow strip between their upper half and the maxilla, and abuts on the maxillary palpus cephalad. Second legs may not reach so far cephalad as the maxillary palpus, but extend caudad as far as the junction of the fourth and fifth abdominal segments. From beneath them, and extending farther caudad
to meet in the mid-line, are the tibiae of the third legs. The tibiae of 2 appear from beneath the caudal extremity of the first legs and reach about half-way between the caudal extremities of the second and third coxae: Third legs appear from beneath their corresponding tibiae. They meet in the mid-line and extend as far caudad as the upper border of the last segment. Antennae narrow, slightly tapering, segmented, but not deeply; terminate in the female between the caudal extremities of the third coxae and second legs; in the male extend, together with the forewings, to the caudal extremity of the last abdominal segment. Coxae of all three legs broad, the first longer than the second and these longer than the third. A small area of the ventral surface of the abdomen is disclosed between the caudal extremities of the last coxae. Forewings in female terminate
Pupa of N. perissopa
Fig.8.—Ventral view. a, antenna; mp, maxillary palp; I, labrum; c, clypeus; f, front; Ip, labial palpi; m, maxilla; l l1, first leg; l2, second leg; l3, third leg; fl1,femur of first leg; c1, first coxa; c2, second coxa; c3, third coxa;tl2, tibia of second leg; tl3, tibia of third leg; w, wing.
Fig. 9.—Dorsal view, v, vertex; f, front; a, antenna; pt, prothorax; mst, mesothorax; mtt, metathorax; w, forewing; wh, hindwing; A1, first abdominal segment; ds, dorsal spines.
Fig. 10.—Lateral view.
in a pointed extremity just above the caudal extremity of the third legs; in the male extend to the lower margin of the last abdominal segment. Hindwings–occasionally a very narrow slip of these is to be seen between the third legs and forewings, and extending very slightly caudad to these latter.
Dorsally : Front shallow; prothorax very narrow; mesothorax large; metathorax about half the length of the mesothorax. Hindwings extend caudad as far as the second abdominal segment. Spiracles on prominent elevations, segments 1 to 8 inclusive, the largest being on 2. Segments 3, 4, 5, 6, and 7 in the female bear a row of small spines somewhat irregularly distributed so as almost to form two transverse lines at the upper extremity of each segment; the male has these on segment 8 also; they are interrupted in the mid-line by a slight medio-dorsal ridge. Under a fairly
high power the body-surface is seen to be roughened with light transverse rugae. Segment 10 bears a pair of short brown upturned spines. It should be noted that the figure was taken from a dried specimen, and so does not show the rounded fullness of the fresh pupa. Movement can take place between all the abdominal segments with the exception of the soldered caudal ones.
|Measurement at||Length from Extreme Front.||Transverse Diameter.||Ventro-dorsal Diameter.|
|Upper border of maxillary palpi||0.28||0.76||0.55|
|Bottom of labial palpi||0.55||0.93||0.66|
|Bottom of first legs||1.00||1.10||0.69|
|Bottom of second legs||1.55||1.07||0.71|
|Bottom of third legs||2.31||0.41||0.48|
The pupa is extruded as far as its caudal segments through the slit. Dorsal splitting takes place along the central vertical line of the mesothorax, prothorax, and vertex; transversely along the epicranial suture. The antennae become detached and are retained only by a small slip of the vertex dorsally; in this manner the headpiece is freed both dorsally and laterally, but is held ventrally by the mouth-appendages.
(11.) Nepticula tricentra Mey. (The Groundsel Nepticulid).
Nepticula tricentra Meyr., Trans. N.Z. Inst., vol. 21, p. 187, 1889; vol. 47, p. 231, 1915.
Meyrick's Original Description.—“♀. 6 mm. Head and palpi grey-whitish. Antennae, thorax, and abdomen grey. Legs dark grey, apex of joints whitish. Forewings lanceolate; pale grey, irrorated with darker; two or three small round black dots in an irregular longitudinal series towards middle of disc : cilia light grey. Hindwings and cilia light grey.”
General Notes.—The amount of dark irroration varies greatly, in some specimens being very light and the three black spots very conspicuous, in others it is very dense and in places leaves irregular paler areas on wing, these tending to form a pale transverse bar across wing at ¾ and in the region of ⅓. The male is a most minute moth, 4–5 mm., but otherwise differs in no marked particulars from the female. It might be more correct to say that the ground-colour of the wing was light yellowish-brown, and irrorated with dark grey to black scales more or less condensed into three rather diffuse transverse bars across wing, one in the region of the base, one somewhat constricted in the middle at ½, and the third occupying the terminal ¼ of the wing; in the middle of each of these bars the scales are condensed to form a small spot. In perfect specimens there is a black cilial line. In some specimens the dark irroration is regularly distributed throughout the wing, and in such cases there is no evidence of transverse marking.
I have found this moth in Wellington and in Dunedin, where it is common. Larvae were found in May, July, August, November, and December. Meyrick records one specimen from Christchurch, in March.
Senecio bellidioides. It is usually only the lower leaves that are attacked.
The Ovum and Egg-laying.
The egg is most inconspicuous. It is, however, like all the other Nepticulid eggs, relatively large; oval, wafer-like, domed above, and rather wider at the micropylar end. Colour pale greenish-yellow. Laid singly and well attached to the under-surface of the leaf, usually against one of the coarser veins, but otherwise in no fixed position. The shell is shiny, unsculptured, transparent, and extremely fragile. After the hatching of the larva it crumples up, rarely persisting long at the end of the mine. Average dimensions are 0–30 mm. by 0–20 mm. Laid singly, often a number on one leaf.
The Mine. (Plate XLII.)
This is a simple, narrow, exceptionally tortuous gallery, more closely applied to the upper than to the lower surface of the leaf. It is not till about half-way through the larval stage that the mine becomes at all conspicuous. In the earlier half of the mine the larva may cross its tracks time and again, and those of neighbours also if these happen to be in the way. Viewed under the Microseope by transmitted light this early part of the the mine is a beautiful object. On the upper surface of the leaf it has a silvery appearance when held in the light, otherwise is greyish in colour. A number of mines may be constructed in a single leaf and the entire leaf-substance consumed. In the last 2 cm. of the mine the gallery is
considerably widened, its edges scalloped and irregular, and owing to its tortuousness this part frequently resembles a blotch. The frass is black, fairly copious, and occupies a more or less unbroken central line; it is homogeneous in consistency, and rests on the floor of the mine. The midrib of the leaf is a barrier in the early stages, but the final part of the gallery frequently crosses it. Average length of the mine, 3 in. to 4 in.; final width, 2 mm. to 4 mm. The larva makes its exit through the upper cuticle. I have rarely found the mine more than 12 in. to 18 in. from the ground. In one specimen under observation the final 2 cm. of the gallery were mined in four days.
Length when fully fed, 4–5 mm. Ground-colour bright grass-green; dorsal band yellowish-brown, more greenish in younger larvae. Segments not deeply incised; body cylindrical, caudal attenuation gradual. Head light amber-brown. Cephalic ganglia and ventral chain not noticed in any specimens. Prolegs as in other Nepticulid larvae. The dorsal linear structures in segment 10 are situated caudo-lateracl and are not very noticeable dorsally. Setae relatively short, about one-third the length of the corresponding segment. Body-pile relatively coarse. The larva mines dorsum uppermost.
This is of the same shape as that of N. ogygia; mussel-shaped, with flattened anterior lip. Constructed of fine silk closely woven to form a thin weatherproof skin. Average size, 2 mm. by 2–5.3 mm. Is surrounded by a scanty amount of loose silk. The cocoons are spun amongst dead herbage around, the food-plant, a favourite place being between the stem and the base of the leaf-stalk of the food-plant itself. Colour on construction white, changing to green and later to dark brown. All cocoons found in the open were brown, whereas the great majority constructed in captivity in a dry box were white or very pale green, and these when placed in a moist atmosphere weeks later turned brown within twelve hours, so there is no doubt that moisture affects the colour of the silk. In captivity a number of cocoons were very minute, being only about half the normal size; these were most likely constructed by poorly nurtured larvae, since it was not a matter of difference of sex. The imagines in these cases were very minute. The larva remains dormant in the cocoon for about a week before the final moult.
Ventral view : Front prominent, bluntly rounded in the male, somewhat bluntly pointed in the female. Last segment usually hidden behind the caudal extremities of the third legs and forewings. Eye two-thirds covered by the basal joint of the antenna and maxillary palp. Maxillary palpus reaching from the antennae to the labrum, of which it sometimes falls rather short; covers the caudal margin of the eye. Labial palpus narrow, extends slightly farther caudad than the maxillae. Maxillae triangular, with the base against the lower border of the maxillary palpus. First legs stout, broadest in their upper half, extend as far as the caudal extremities of the second coxae in both sexes. The femur occupies a small narrow slip separating the upper extremity of the first leg from the maxilla, more noticeable in the male. Second legs reach to about half-way between the caudal extremities of the first and second, their narrowed cephalic extremity reaching the lower border of the maxillary palp. The second tibiae do not appear; the third appear only very slightly from beneath the tips of the second legs.Third legs meeting in the mid-line shortly after appearing from under the antennae lateral to the extremities of the second legs, thereafter extend in both sexes as far as the lower border of the last abdominal
segment. Antennae narrow, segmented, extend slightly beyond the second legs in the female, slightly farther in the male to the point where the third legs meet in the mid-line. Coxae—the first relatively large, the second and third very narrow, the second smallest and greatly reduced by the first legs. The amount of ventral abdominal surface showing between the last coxae and the legs is small. Forewings terminate in both sexes a short distance above or below, or on the same level with, the third legs. Hindwings not seen on this surface in either'sex.
DoTsally : Prothorax almost obliterated in the mid-dorsal line. Spiracles prominently elevated on all segments 1 to 8. Dorsal spines forming a relatively broad band, three or four deep, transversely across the upper third of segments 3 to 7 inclusive in the female, and 3 to 8 inclusive in the male. Each band is interrupted in the mid-dorsal line. The pair of small upturned dorsal hooks is situated on segment 10 in the male, on 9 in the female. Movement takes place between all the abdominal segments excepting the last three. Colour at first bright green, becoming somewhat yellowish, and later dark grey to black. The only note I have regarding the pupal duration is—“Pupated 25th May, 1919; emerged 14th July, 1919: forty-nine days.”
|Measurement at||Length from Extreme Front||Transverse Diameter.||Ventro-dorsal Diameter.|
|Upper border of maxillary palpi||0.34||0.67||0.51|
|Bottom of labial palpi||0.48||0.77||0.57|
|Bottom of first legs||1.07||0.94||0.64|
|Bottom of second legs||1.41||0.80||0.67|
|Bottom of third legs||2.07||0.20||0.10|
The pupa emerges as far as the sixth or seventh abdominal segment. The headpiece is separated laterally by the separation of the antennae, and dorsally by splitting along the epicranial suture. Vertical splitting takes place along the central line of the mesothorax and prothorax, and vertex dorsally. The antennae remain attached by a small slip of the vertex only.
(12.) Nepticula fulva n. sp. (The Olearia Blotch Nepticulid).
Female. 8 mm. Head and prothorax light yellowish-brown; antennae under 1 and over ½ dark brown; abdomen dark grey; legs light-brownish: Thorax and forewings pale-whitish densely irrorated with darker brown scales; a small irregular black spot in wing near dorsum at ¼, another in centre a little beyond ½, a third in centre of wing near termen; the central spot is the most constant. Cilia light brown, a brown cilial line found only in very perfect specimens; the whole wing and cilia with bronzy reflections, seen only in some lights. Hindwings and cilia grey-brownish. In the male the brown scales in the forewings are largely replaced by darker grey ones, and the central spots, though still present, are not so prominent.
I have come across this moth only in Dunedin, where its mines are very numerous, and the food-plants are often badly infected. In the last two years I have found larvae in each month except January and February, when I have been out of Dunedin; they may be found at almost any time during the year. Ova were found to be most abundant in April, May, September, and October. The imagines may be found at any time during the summer months; they are active in the sun about the food-plant.
Olearia Traversii (akeake), O. nitida (now O. arborescens and O. divaricata), O. macrodonta, O. Cunninghamii (heketara), O. Colensoi (tupare), O. avicenniaefolia (akeake). Of these, O. nitida and O. macrodonta are the ones most attacked.
The Ovum and Egg-laying.
The egg is relatively large, and when newly laid is bright blue in colour. Empty shells are white and filled with frass. In shape oval, wafer-like, domed above; a narrow flattened and somewhat ragged fringe surrounds the foot. The shell is strong, transparent, shiny, devoid of sculpture except for a slight roughening. Dimensions are—total length, 0.48 mm.; width, 0.38 mm.; height, 0.12 mm. It is strongly attached to the surface of the leaf, and persists for a considerable time even after the mine has been vacated. The eggs are laid singly, but a considerable number may be deposited on one leaf. They are laid on the upper surface, but otherwise have no fixed locality, though the upper and outer two-thirds of the leaves appear to contain the majority of the mines. Some ova may be found laid on entirely dead portions of the leaf, over long-disused mines, and even sometimes upon or overlapping one another, when the larvae must perish. The egg-capacity of the moth is not known. The period of incubation may be anything from seven days to a month, or longer, according to local climatic conditions.
The Mine. (Plate XLIII, figs. 1, 2.)
This is a blotch on the under-surface of the leaf. The hatching of the egg is made known by the leaf-tissue in its immediate vicinity becoming dark purple. This dark-purple spot is the chief naked-eye characteristic of this period distinguishing this species from N. ogygia, being absent in the latter. The larva immediately eats its way through the bottom of the shell into the leaf and descends to the lower cuticle. The first portion of the mine is a narrow, fairly straight gallery (fig. 13), which can be traced on the under-surface of the leaf by a slight prominence of the cuticle; on the upper surface a trained eye can follow its course, as this is marked out by a number of very minute white dots, these being small areas of dry cuticle where the larva has eaten nearer the surface. The average length of this preliminary gallery is about 1 cm., and it now abruptly expands into a relatively large blotch, which at first is more or less roughly circular in shape, but in most cases soon becomes rectangular owing to the coarser ribs of the leaf confining it within their boundaries. The area occupied by the blotch is from 2 to slightly over 3 square centimetres. The larva does not readily attack the coarser cell-walls of the internal leaf-substance, but, separating the lower cuticle from these cells, it attacks the substance within them, thus causing the characteristic external appearance of the
mine on the upper surface of the leaf, and when the under-cuticle is stripped off the mine gives it the honeycomb appearance. The preliminary gallery often becomes absorbed into the blotch. The larger leaves may contain a considerable number of mines; I have found from twenty-six to thirty on one leaf of O. nitida. They occur in any part of the leaf, but the majority in the outer portions. Leaves on all parts of the tree are equally attacked. Neighbouring mines sometimes coalesce and become continuous with one another. The frass is black and granular, and fairly plentiful in the blotch, where it occupies the central two-thirds, being packed into the excavated cell-spaces in the roof of the mine. Many of these cells are entirely emptied of their contents by the larva, and the upper cuticle soon
dries and becomes white externally. As the blotch enlarges, more of these minute dots appear, closer together and more numerous in the central portion of the mine. On the under-surface the blotch can be made out more clearly, owing to the detachment and consequent looseness of the cuticle over the part. In mines still tenanted by the larva the under-surface is more or less bulged, and is slightly lighter in colour than the rest of the leaf. When full-fed the larva eats a small semicircular outlet at the margin of the blotch, through the lower cuticle, and descends to the ground to pupate. The mine is not conspicuous till after the larva has left it, when the part of the leaf affected becomes dead and shows in violent contrast to the rest.
Length when full-grown, about 5 mm. Ground-colour pale green; central marking dark olive-green in its first half, darker in its caudal half. Head pale greyish-brown; darker reddish-brown sutural lines; almost acutely triangular in shape; retractile. Cephalic ganglia and ventral chain not observed. Segments well rounded, moniliform; last three abdominal segments extended, the tenth directed dorsally with narrow dark dorsolateral lines. Setae fine, fairly long. Body covered with a minute pile. Saetal plan has been left for a future paper. Fleshy protuberances take the place of prolegs. The larva mines dorsum uppermost.
This is constructed outside the mine amongst dead foliage at the foot of the food-plant. The colour of the cocoon blends with that of its surroundings and makes it most difficult to find. In the breeding-jars the cocoons are always constructed between two fairly closely applied surfaces in the darkest corners at the bottom of the jar, and they are fairly firmly attached. The construction of the cocoon usually occupies about two
days, after which the larva lays up for a week or more before the final moult; it is likely that the larva hibernates in this fashion. The silk is at first a very pale green, but in almost every case quickly becomes a dark brown. Some cocoons may be lighter in colour than others, and a few remain pale green throughout. The shape is somewhat more quadrilateral than ovoid, the length being about one and a half times the width at the middle; the ends are rounded, and the anterior end is considerably wider than its nadir, and possesses two flattened closely-applied lips which extend the full width of the cocoon. The cocoon is somewhat flattened above and below. The texture is very close, firm, and strong, the silk being so woven as to form a thin skin-like fabric without any pores or openings even when viewed under the microscope. The exterior of the cocoon is provided with a small amount of loose floccy silk, but this is not very noticeable. Average length, 3 mm. to 4 mm. There is no separate inner lining.
Ventral view: Front bluntly rounded, in female somewhat pointed. Terminal segment in male somewhat quadrilateral in shape, slightly broader than long; in the female is bluntly rounded, about twice as broad as long, and fairly deeply notched anteriorly by the gemtal opening. Eye about two-thirds covered by the basal joint of the antenna and maxillary palpus. Maxillary palpus well developed and stretching transversely between the antenna and the labrum. Labial palpi slightly longer than the maxillae.
Maxilla broad above, abuts against the labrum, maxillary palpus, and femur of the first leg; sharply pointed caudad. First legs fairly stout, of almost even diameter throughout; extend from the maxillary palpi to slightly below the caudal extremities of the second coxae in the male, but falling slightly short of this in the female. Only a very small slip of the first femur appears medially at the uppermost extremity. Second legs extend from a narrow pointed cephalic extremity a little below the lateral extremity of the maxillary palpi to about half-way between the caudal extremities of the first and third legs; somewhat expanded opposite the second coxae; the tibiae of 3 appear from beneath their caudal extremities
but only occupy a small area; they are somewhat more evident in the female and almost meet in the mid-line. The tibiae of 2 appear as a slight caudal extension of the first legs, and are more evident in the female. Third legs appear from beneath the caudal extremities of 2, and, meeting in the mid-line, extend in the male as far as the lower margin of the last segment, in the female to a little below the upper margin of the eighth segment. Antennae rather wide, segmented: in the male fall slightly short of the caudal extremities of the forewings and third legs; in the female extend only a slight distance beyond the second legs and third tibiae. Coxae relatively narrow; the first are the longest, and the third are slightly longer than the second. A variable amount of the ventral, abdominal surface can be seen below the third coxae between these and the second and upper part of the third legs. Forewings occupy only a narrow strip ventrally, extending not quite so far caudad as the third legs. A very narrow slip of the hindwings may extend a short distance beyond their tips, more marked in the female.
Dorsally: Prothorax very narrow and almost obliterated in the midline. Spiracles on prominent elevations on segments 1 to 8. A single transverse row of small dorsal spines in the fore part of segments 3 to 7 inclusive in the female, 3 to 8 inclusive in the male; interrupted in the mid-dorsal line. The small pair of dorsal upcurved hooks appear to be on segment 10 in the male and segment 9 in the female. It appears that movement can take place between all the abdominal segments excepting the last three. Colour at first pale green, changing later to dark grey.
Pupal period varies according to climatic conditions. I have reared imagines towards the end of September from larvae that pupated in the middle of July. The following periods are from my note-book: One specimen pupated 28th March, 1920; emerged 30th May, 1919—sixty-one days. Larvae pupated 24th May, 1919; emerged 13th July, 1919—fortynine days. Pupated 15th July, 1920; emerged 28th September, 1920—seventy-five days. During October and November, 1919, pupal period not longer than twenty-one days.
|Measurement at||Length from Extreme Front.||Transverse Diameter.||Ventro-dorsal Diameter.|
|Upper border of maxillary palpi||0.30||0.77||0.52|
|Bottom of labial palpi||0.61||0.98||0.63|
|Bottom of first legs||1.10||1.08||0.70|
|Bottom of second legs||1.70||0.90||0.77|
|Bottom of third legs||2.40||0.30||0.30|
Vertical splitting takes place dorsally along the mid-line of the mesothorax and prothorax, and transversely along the epicranial suture. The antennae become almost completely detached, only a small slip of the vertex retaining them dorsally; thus the head is freed laterally and dorsally, but remains attached ventrally.
Before emergence the pupa is extruded from the cocoon as far as the fourth or fifth abdominal segment