Art. 34.—The Leaf-mining Insects of New Zealand: Part III—Species belonging to the Genera Agromyza (Fallen) and Phytomyza (Fallen) (Diptera).

By Morris N. WattF.E.S.

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(13.) Agromyza umbrina n. sp. (The Veronica Blotch-fly).

The Imago.

Male. Frons more than half the width of the entire head, dark grey to black with a slight yellowish tinge; antennae, palpi, genae, occiput, and ocellar triangle black; proboscis yellowish; eyes dark red-brown; each orbit with four strong bristles; ocellar and post-vertical bristles strong; arista pubescent.

Thorax black, shining; lateral margins in front of wing-bases yellowish; four to six series of setulae between the three pairs of dorso-centrals; prescutellar acrostichals absent; scutellum entirely black.

Abdomen dark greenish-grey to black, shining; ventro-lateral margins obscurely yellowish; under-surface lighter grey tinged with yellowish.

Legs black; upper joint of tarsus paler.

Wings (fig. 21) greyish, bases yellowish, veins black. Costa to apex of fourth vein, the latter ending in the tip of the wing; penultimate section of fourth vein about one-sixth as long as ultimate, and one-fourth as long as ultimate section of the fifth. Halteres lemon-yellow.

Female similar to male, slightly larger.

Length, about 2·5 mm. (♂).

Type in author's collection; reared from mines obtained in Botanical Gardens, Dunedin.

Distribution.

At present only recorded from Dunedin, where it is fairly common. Imagines easily reared from the mines, but more easily caught while resting on the leaves of the food-plant; the younger leaves and young buds are the most favoured situations in which to find the flies ovipositing and feeding. To be found throughout the summer months; there may be

three to four generations. Imagines found in the greatest numbers during February, April, October, and December.

Easily distinguished from A. flavocentralis, also common on the same food-plant, by its darker colour, and especially by absence of yellow spot on the scutellum, which in the latter species is a most conspicuous mark.

Food-plants.

Has been reared from Veronica speciosa, V. salicifolia (koromiko), and a number of the larger-leaved hybrid veronicas.

Egg-laying and Larva.

Ova laid singly and deposited in minute pockets under cuticle of the leaf. Youngest leaves most favoured. No fixed situation on the leaf, though majority of pockets constructed in vicinity of midrib, and practically invariably on underside of leaf, this, of course, being the outermost and only available surface in the buds, which are the favourite site for oviposition. Duration of egg stage not known; possibly not longer than a fortnight.

Full-grown larva about 4 mm. in length, yellowish-green, shiny. First moult takes place in preliminary gallery on underside of leaf; second moult normally about 6 mm. along the mine on upper side of leaf. Pharyngeal skeleton fairly stout; number of teeth on mandibular sclerite in all three instars is two. Length of pharyngeal skeleton, exclusive of mandibular sclerite—first instar, 0·20 mm.; second instar, 0·30 mm.; third instar, 0·43 mm. Length of mandibular sclerite—first instar, 0·03 mm.; second instar, 0·05 mm.; third instar, 0·08 mm.

The Mine. (Plate 38, fig. 3; Plate 40, fig. 6.)

Mine is a composite one, consisting of gallery and blotch. Gallery portion mainly situated on under-surface of leaf; narrow and so closely looped back and forth that the various portions eventually anastomose and form a false blotch; this part of the gallery may be 4–7 cm. in length, but owing to looped character the false blotch will rarely exceed 1·5 cm. in length; direction is in the long axis of leaf, and mine usually close against midrib; colour pale green, earlier parts whitish; frass scanty, very fine, scattered. Many larvae spend the winter months in this preliminary part of the mine.

Larva sooner or later leaves under-surface and mines close up against upper cuticle, the mine rapidly widening so as to form eventually a pear-shaped blotch. Margins shallowly dentate. Average size of blotch—length, 2·5 cm.; greatest diameter, 1·25 cm. Direction of blotch, as a rule, from region of midrib towards apex of leaf; midrib does not form a serious obstruction to this part of mine. Blotches most commonly found in central third of leaves. No indication of blotch on underside of leaf, excepting, of course, preliminary gallery; on upper surface the colour rapidly becomes dark brown or grey, in fresher portions dark green in centre and pale around margin. Cuticle over blotch becomes crinkled and mine has appearance of being slightly inflated. “Herring-boning,” caused by larva's habit of feeding (see Plate 38, fig. 3), very marked. Frass coarse, of semi-fluid consistency, relatively scanty, deposited mostly on roof of mine in track of larva. In larger leaves several mines occupy same leaf, but galleries and blotches of different larvae never anastomose.

The Pupa. (Plate 38, fig. 4; text-figs. 11, 12.)

Pupation, consisting of hardening of larval skin, takes place within blotch-mine, and, except for a short white thread extending from anal aperture to floor of mine, pupa lies free within blotch. Dorsum of pupa evenly rounded, greatest height about middle; segments well rounded and become narrowed cephalad, practically devoid of sculpture, but bear four or five rows of very minute spines on sides anteriorly; just below mid-lateral line each segment slightly prominent anteriorly, an obscure shoulder being thus formed; in mid-dorsal line segments are somewhat hollowed cephalad. Anterior respiratory processes short and set close together on small prominence; they project almost directly upwards and outwards, are expanded at tips, and are slightly overhung by first segment; second segment tends to overhang first, and the next to last segment is prominent posteriorly. Posterior respiratory processes relatively large and prominent, mushroom-shaped; below them last segment bluntly prominent and shows the slightly sunken anal aperture. Colour of pupa rich dark brown, assuming a black colour prior to emergence of fly, due to dark colour of this latter; empty pupa-cases a rich golden-brown.

Average dimensions: Length, 2·6 mm.; greatest dorso-ventral diameter, 1·2 mm.; greatest lateral diameter, 1·45 mm.

On dehiscence dorsal halves of first three and a half segments lift up in one piece, ventral halves of same segments also break away in one piece around transverse suture. Both plates, however, remain more or less attached to puparium by pieces of membrane. Emergence of fly has not been observed, and it is difficult to understand just how it is done: it is known that it emerges by means of a short slit in upper surface of leaf at margin of blotch; possibly this slit is prepared by larva, but no sign of it has been found in mines from which flies had not yet emerged.

Duration of pupal period, about thirty days, normally.

(14.) Agromyza umbrinella n. sp. (The Minute Veronica Blotch-fly).

The Imago.

Male. Head black; frons with obscure greyish tinge; proboscis obscurely yellowish; eyes dark red-brown; each orbit with three strong bristles; ocellar and post-vertical bristles strong and of nearly equal size.

Thorax—dorsum black; three pairs of strong dorso-central bristles, the setulae between them sparse, and arranged in three or four irregular series; pleural sutures obscurely yellowish; lateral margin of thorax in front of wing-bases obscurely yellowish; scutellum black, obscurely greyish in centre.

Abdomen dark grey; tergites tinged with yellowish posteriorly; sides and under-surface yellowish.

Legs black.

Wings (fig. 22) dark grey, veins black. Penultimate section of fourth vein about one-eighth the length of the ultimate, and about one-fifth as long as ultimate section of the fifth; halteres lemon-yellow.

Length, 1·5 mm.

Type in author's collection; bred from mines from Woodhaugh Gardens, Dunedin.

Distribution.

First discovered in Woodhaugh Gardens, Dunedin, 29th June, 1919, by Mr. W. G. Howes. Not by any means a common fly, and specimens

have only been procured by rearing from the mines. Has been found on Swampy Hill, Dunedin; and I have found the mines at an elevation of 3,000–5,000 ft. on north and south sides of Mount Ruapehu in January, 1921 and 1922 (scarce). In Dunedin imagines have emerged towards end of March, and during September.

Food-plant.

Veronica Colensoi.

Egg-laying and Larva.

Eggs laid singly in minute pockets beneath under-cuticle of leaf. From examination of large number of specimens position of egg-pocket appears constant—close against outer margin of leaf and about 3 mm. from apex.

Full-grown larva about 2 mm. in length, pale greenish-orange, shiny. Particulars of stadia and duration of larval existence unknown. Pharyngeal skeleton of final instar 0·35 mm. long, exclusive of mandibular sclerite; this latter process possesses two teeth, its length being 0·07 mm.

The Mine. (Plate 40, fig. 7.)

Course of mine very constant, direction at first being along margin of leaf towards apex; here, crossing midrib, it continues down opposite margin towards base. From egg-pocket to midrib, gallery narrow and expanding but little; then, however, widening rapidly so as soon to occupy whole of one-half of leaf. Margins of gallery minutely irregular. Up to this time mine entirely on underside of leaf, there being no evidence of it on upper; larva now commences to mine close under upper cuticle and excavates a blotch, which, as a rule, includes entire upper surface of leaf; occasionally only half leaf may be blotched, and in such cases it is usually distal half. Midrib is no barrier to progress of blotch. Frass relatively plentiful, black, semi-viscid, and in gallery forms a more or less unbroken expanding central band; in blotch it is distributed more haphazard. Early part of mine pale green with darker centre and almost white margins; in older blotches containing pupae entire upper surface of leaf more or less rich grey-brown, paler and with yellowish tinge around margin. Completed mine has characteristic inflated appearance, as though the leaf had been blown out. Average length of gallery, 1 cm.; average area of blotch, 20 sq. mm. Discoloration of leaf does not extend beyond boundaries of mine. Never more than one mine in a leaf.

The Pupa. (Figs. 3 and 4.)

Larva pupates within blotch-mine, where, except for short thread attaching its posterior end to floor of mine, it lies free. Colour at first whitish, rapidly becoming jet-black. Though smaller, it is very similar to that of A. umbrina.

Average dimensions: Length, 1·86 mm.; greatest ventro-dorsal diameter, 0·76 mm.; greatest transverse diameter, 1 mm.

Duration of pupal existence doubtful—possibly not longer than thirty days under normal conditions. Only one record in my notebook: four larvae pupated 16th July, 1919, and imagines emerged 10th August, 1919 = twenty-five days. Dehiscence similar to that of A. umbrina, and fly escapes from mine by means of minute slit in side of leaf near base.

(15.) Agromyza flavolateralis n. sp. (The Whiteywood-fly).

The Imago.

Male. Frons about one-third width of head, yellow; ocellar triangle black; antennae orange, arista pubescent, black; proboscis, palpi, and genae yellow; occiput black; eyes dark brown; each orbit with four bristles; ocellar bristles shorter than post-vertical pair.

Fig. 1.—A. flavopleura, pupa, lateral view.
Fig. 2.—The same, dorsal view.
Fig. 3.—A. umbrinella, pupa, lateral view.
Fig. 4.—The same, dorsal view.
Fig. 5.—A. clianthi, pupa, lateral view.
Fig. 6.—The same, dorsal view.
Fig. 7.—A. citreifemorata, pupa, lateral view.
Fig. 8.—The same, dorsal view.
Fig. 9.—A. flavolateralis, pupa, lateral view.
Fig. 10.—The same, dorsal view.
Fig. 11.—A. umbrina, pupa, lateral view.
Fig. 12.—The same, dorsal view.
Fig. 13.—A. flavocentralis, pupa, lateral view.
Fig. 14.—The same, dorsal view.
Fig. 15.—P. climatadi, pupa, lateral view.
Fig. 16.—The same, ventral view.
Fig. 17.—P. albiceps, pupa, lateral view.
Fig. 18.—The same, ventral view.
Fig. 19.—A. umbrosa, pupa, lateral view.
Fig. 20.—The same, dorsal view.

(Camera lucida sketches; all to same scale.)

Thorax black, shining; lateral margins in front of wing-bases, and sutures of pleura, broadly greenish-yellow; scutellum obscurely pale in centre; two strong posterior and two weak anterior pairs of dorso-centrals.

Abdomen very dark grey to black; ventro-lateral margins narrowly light grey-greenish.

Legs dark with knee-joints and bases of tarsi paler, yellowish.

Wings (fig. 23) greyish, veins fuscous; calyptrae grey, fringes fuscous; costa to apex of fourth vein, the latter ending in tip of wing; penultimate section of the fourth vein about one-tenth as long as ultimate. Halteres pale yellow.

Length, 2 mm. Female slightly larger than male, but otherwise similar.

Type in author's collection; reared from mines obtained in Botanical Gardens, Wellington.

Distribution.

First discovered in Botanical Gardens, Wellington, 22nd June, 1919. Fairly plentiful in Wellington, and has also been found in Wanganui district. Not yet found in South Island. Imagines appear in October and November.

Food-plant.

Melicylus ramiflorus (mahoe, whiteywood).

Egg-laying and Larva.

Ova laid singly in minute pockets beneath under-cuticle of leaf, generally in vicinity of midrib, in distal half of leaf.

Full-grown larva—length, 3 mm.; pale green, shiny, darker posteriorly with touch of yellow; cylindrical, bluntly rounded caudad, slightly attenuated cephalad; respiratory processes black. Larva undergoes three stadia, duration of which are not known, but situations of moults in mine are given in next paragraph. Mandibular sclerite possesses but two teeth in all three instars. Larval existence of about twenty-one days' duration. When fully fed it cuts a semicircular slit in upper epidermis of leaf at end of mine and pupates amongst vegetation near or on ground. In breeding-dishes larvae always pupated under cover of leaves, and pupation occurred within a few hours of emergence from mine; in dishes provided with fine sand and earth many of larvae pupated on surface of this, but never penetrated into it. Pupation has never been found to take place within mine.

The Mine. (Plate 41, figs. 3, 4, 5.)

Mine a conspicuous white or pale-green gallery on upper side of leaf. Entire mine is close under upper cuticle, first 3 cm. or 4 cm. being much closer against cuticle than the rest, and consequently white in colour and slightly more conspicuous. After second moult, which occurs when mine is about 3 cm. long, colour of fresh mine is pale green, owing to larva mining deeper and thin layer of leaf-substance intervening between mine and cuticle. No discoloration of leaf external to mine. Gallery widens evenly from about 0·5 mm. at start to 3–4 mm. at termination; margins are shallowly scalloped; direction more or less erratic and angulated owing to tendency to follow coarser veins of leaf—at times mine may be much looped upon itself, and may send out short blind branches. Where portions of later gallery happen to cross first 2 cm. or 3 cm. they do not anastomose, later portion passing beneath earlier. General trend of mine is in long axis of leaf, and midrib is rarely crossed except by later portion of mine, and then usually only in distal third. First moult occurs at a point about 1 cm. from start; positions of moults easily found by holding leaf up against light and searching for cast pharyngeal skeleton with hand-lens; where these casts are found it will be noticed that in immediate vicinity there is less frass than elsewhere, and mine at this point may be slightly enlarged

on one side. Roof of mine slightly domed over larva. Frass deposited in semi-viscid state, scanty, dark green to black; in early part of mine it occurs in two thin parallel more or less interrupted lines of minute granules along sides of gallery; later deposits, are larger and more or less smeared over roof of mine, and are usually placed alternately towards first one side of mine and then the other. “Herring-boning” very plain. Under adverse conditions, as when leaves are picked while larvae still very young, there is a tendency for mine to become longer than normal, more tortuous, branching, and deeper in tissues. Colour of mine on underside of leaf a shade paler green than elsewhere, and but for this there is little evidence of it here. Rarely more than two or three mines in any one leaf. Average length of mine about 9 cm. Mines should be looked for during September.

Fig. 21.—A. umbrina.
Fig. 22.—A. umbrinella.
Fig. 23.—A. flavolateralis.
Fig. 24.—A. flavocentralis.
Fig. 25.—A. umbrosa.
Fig. 26.—A. citreifemorata.
Fig. 27.—A. clianthi.
Fig. 28.—A. flavopleura.
Fig. 29.—P. albiceps.
Fig. 30.—P. clematadi.

(Camera-lucida sketches; all to same scale.)

The Pupa. (Figs. 9, 10.)

Formed by hardened larval skin. At time of pupation larva ejects all unutilized food-material in form of a green fluid, and this serves to cement puparium to its support. Colour of pupa grey-brown; in some instances almost jet-black, due as a rule to presence of a parasite. Dorsum somewhat humped in region of fifth and sixth segments; cephalic extremity bluntly pointed; laterally anterior segments are slightly expanded about midlateral line to form on either side of puparium a bluntly-rounded ridge or shoulder bearing the horizontal suture. Anterior respiratory processes situated close together dorsal to suture; they are short, with small black expanded tips, and directed upwards and forwards. Segments moderately rounded, narrowed cephalad, marked with minute annular striae, and minutely pitted in intersegmental regions; dorsum of each segment bears a shallow pit in mid-line close against caudal margin. Last segment large; postero-dorsally it bears posterior respiratory processes, which are directed

backwards, and are stouter and farther apart than anterior pair, but, like these latter, have black expanded tips; below and lateral to post-respiratory processes is a small prominence on either side, and between and below these is situated the posterior aperture.

Average dimension: Length, 1·86 mm.; greatest transverse diameter, 1·04 mm; greatest height, 0·89 mm.

Duration of pupal period normally eighteen days. Dehiscence similar to that of other species already described.

(16.) Agromyza flavocentralis n. sp. (The Veronica Gallery-fly).

The Imago.

Male. Eyes dark reddish-brown; occiput and ocellar triangle black; frons lemon-yellow; area at base of antennae, scape, pedicel, and arista black, terminal segment orange; clypeus black; proboscis and genae lemon-yellow, palpi darker; three strong bristles along each orbit (some specimens possess a fourth weak pair below); ocellar bristles as long as post-verticals.

Thorax black, shining; dorso-lateral margin in front of wing-base yellow, pleura very narrowly yellow on sutures; setulae between dorso-centrals long and sparse, forming 3–4 irregular series; anterior two pairs of dorso-centrals weaker than the two posterior pairs; scutellum broadly yellow in centre from base to apex.

Abdomen black; intersegmental incisions showing pale-yellowish when abdomen is distended; ventro-lateral margin pale-yellowish.

Legs black; apices of femora yellow, first three joints of tarsi darker yellow.

Wings (fig. 24) pale-greyish, veins black; penultimate section of fourth vein as long as ultimate section of fifth, penultimate section of fifth vein over one-half as long as ultimate. Halteres yellow.

Length, 2·75 mm. Female slightly larger than the male.

Type in author's collection; reared from mines obtained in Botanical Gardens, Dunedin.

Distribution.

Appears to be widely distributed. First found on Mount Egmont, at 3,000–4,000 ft. (common), January, 1917, and again in April of same year. Has also been found since at Wanganui, Wellington, and Dunedin (common). Mr. Tapley has sent me mines from Governor's Bay, and reports it common about Christchurch. Mr. C. C. Fenwick secured mines on Milford track in January, 1921. Imagines may be caught on food-plant throughout summer months.

Food-plants.

Veronica salicifolia (koromiko), V. speciosa, and a large number of the larger-leaved hybrid veronicas.

Egg-laying and Larva.

Ova laid singly in small pockets beneath under-cuticle of leaf, most usually in proximal half. Duration of egg stage possibly not longer than a fortnight under favourable conditions. Egg-pockets soon become discoloured, dark brown to black, and are then very conspicuous on both surfaces of leaves; they can easily be distinguished from similar spots caused by blight by the small transparent centre. They are often to be

found in short series, half a dozen or so, and none of these may contain an ovum; they have been made by the same individual for purposes of refreshment only, the exuding sap from the freshly punctured hole being eagerly sucked up. The majority of the “egg-pockets” are really constructed for this purpose—apparently a common habit among most leafmining flies.

Full-grown larva—length 4 mm., pale-yellowish anteriorly, dark green posteriorly, shiny. Larval existence from two to four weeks under favourable conditions. Number of instars three; number of teeth on mandibular sclerite in each instar two. Length of pharyngeal skeleton, exclusive of mandibular sclerite—first instar, 0·18 mm.; second instar, 0·25 mm.; third instar, 0·37 mm. Length of mandibular sclerite — first instar, 0·05 mm.; second instar, 0·08 mm.; third instar, 0·1 mm. First moult occurs at a point in mine about 1·5 cm. from start, second moult about 5–6 cm. from start.

The Mine. (Plate 38, fig. 1; Plate 40, figs. 1–3, 5.)

A long, narrow gallery, margins practically parallel except in last two or three centimetres, where mine widens considerably and margins become irregular and scalloped. Mine close against upper cuticle of leaf throughout its whole extent; little indication of it on under-surface, but above it is most conspicuous. Course irregular and serpentine, frequently markedly vermiform in character, contiguous loops running so close as almost to form a blotch of the whole. Total length of mine averages about 14 cm. First one or two centimetres frequently closely looped around egg-pocket and would appear to be wound spirally round it for six or seven turns, and in some of the larger fleshy-leaved veronicas this is actually the case. “Herring-boning,” caused by the manner of feeding, is a very marked characteristic (see Plate 38, fig. 1). and makes the mine a most beautiful object when viewed by transmitted light with the low powers of a microscope. In the long narrow-leaved veronicas it is usual to find gallery following margin of leaf very closely; midrib forms a barrier in its proximal two-thirds. Occasionally gallery is closely looped upon itself across one-half of leaf, and area is just saved from being a blotch through intervening walls between the loops not being broken down; this type of mine frequently occurs when egg has been laid in vicinity of tip of leaf. Mine conspicuous on account of its dark colour, the cuticle covering it rapidly dying and becoming brown, and the frass showing darkly through it all along, causing the mine in its freshest portion to appear a darker green than surrounding leaf-surface. Frass not abundant; very dark green when fresh, but rapidly becomes black; deposited in a semi-fluid form, and occupies one or other side of mine in an interrupted line of small particles which adhere chiefly to roof of gallery. Frass-line does not keep to same side of mine throughout its length, but alternates in longer or shorter lengths, first on one side and then on other; where the mine is closely looped frass-line may occupy left side along one length and right side in next, this being due to the fact that the larva mines upon its side, and when it makes a sudden change of direction it has to turn over upon the opposite side, by so doing avoiding doubling upon itself in a narrow passage. Seldom more than one mine in a small leaf, though a large leaf may contain two or three. When full-grown, larva emerges by semicircular cut in epidermis of leaf at end of mine; in almost every case escape is made through roof of gallery. Position of moults can easily be found as before.

From an examination of the mines it would appear that there is a distinct variety of this fly, for the following constant type has often been found. Mine a rapidly-widening pear-shaped gallery (see Plate 40, fig. 5), very dark coloured at apex and in central portion and pale along margins. Frass deposited in central line only, except in very early part, where there is tendency for it to be in two rows. “Herring-boning” occurs transversely across mine in close outwardly convex curves. Margin of mine slightly scalloped. Frequently terminal centimetre or so considerably narrower than middle portion. Average length of mine 4–5 cm., greatest average width 8 mm. Larva almost invariably escapes from mine through lower cuticle. Larvae slightly heavier built with a somewhat heavier pharyngeal skeleton than the long narrow-gallery type; pupae darker in colour and slightly larger, and in the breeding-jars were far less securely attached to their support. The mine, however, is a very distinct feature. A long series of both flies have been reared, but superficially show no differences, so one hesitates to go further at present than simply state the facts.

The Pupa. (Figs. 13, 14.)

After emerging from the mine, larva pupates on or near ground; in breeding-jars larvae never penetrated beneath surface of sand. Pupa is pale amber in colour; dorsal outline well rounded; segments moderately rounded, shiny, unsculptured, possessing microscopic spines cephalo-laterad, slightly produced cephalad in mid-dorsal line. Antero-lateral “shoulder” not well developed. Anterior spiracles short, black, and relatively close together; posterior stout, black, on strong tubercles, and relatively wide apart. Posterior ventro-lateral tubercles well marked. Anal aperture on a small elevation ventrad.

Average dimensions: Length, 2·41 mm.; greatest ventro-dorsal diameter, 1·17 mm.; greatest transverse diameter, 1·21 mm.

Duration of pupal stage: The following dates are from my fieldbook: Larvae pupated 6th January emerged 30th January=24 days; 1st July to 30th August=60 days; 20th March to 28th April=39 days. Dehiscence identical with that of species already described.

(17.) Agromyza umbrosa n. sp. (The Small Veronica Gallery-fly).

The Imago.

Male. Frons and genae green-yellowish, covered with a minute black pubescence; eyes dark-reddish; occiput, ocellar triangle, antennae, and palpi black; each orbit with four strong bristles, the lower two convergent across the face, the upper two erect; ocellar bristles as long as or slightly longer than the post-verticals; arista pubescent; third joint of antennae as long as second; proboscis greenish-yellow.

Thorax black, shining; lateral margins in front of base of wings, and pleural sutures, greenish; scutellum with an obscure broad antero-posterior band of greenish-grey; four series of setulae between the four pairs of dorso-centrals; anterior two pairs of dorso-centrals only slightly weaker than the posterior two pairs.

Abdomen very dark grey to black on dorsum; posterior margins of tergites greenish; sides yellowish-green; under-surface dark grey with yellowish-green intersegmental regions.

Legs entirely black.

Wings (fig. 25) pale-greyish, veins darker grey; ultimate section of fourth vein eight and a half times as long as penultimate section, the latter one-fifth as long as ultimate section of the fifth; penultimate section of fifth two-thirds as long as ultimate. Halteres very pale lemon-yellow.

Length, 2 mm.; length of wing, 2 mm.

Type in author's collection; reared from mines obtained in Botanical Gardens, Dunedin.

Distribution.

Has only been found in the Botanical Gardens, Dunedin. Larvae starting mining in early November started to pupate beginning of December, imagines emerging about 22nd December.

Food-plant.

Apparently confined to Veronica monticola.

Egg-laying and Larva.

Egg laid in a small pocket under lower cuticle of leaf, almost invariably within 1 mm. of extreme tip and about half-way between midrib and outer margin.

Full-grown larva, length 3 mm.; yellow in anterior half, dark green posteriorly, shiny. Larvae have been found mining in February, March, and November.

The Mine. (Plate 40, fig. 4.)

A simple gallery, varying in length from 2·5 cm. to 4 cm. Larva, on hatching, mines at once to upper surface of leaf, and thenceforth mines closely under upper cuticle. At first the gallery closely follows outer margin of leaf as far as its basal quarter, and then turns back between its previous course and midrib, which forms a barrier till larva is fairly matured; enclosed between these narrow limits practically all the leaf-substance between the two cuticles is removed; soon the larva is able to break through midrib, generally near apex of leaf, and continues mining in opposite half, there being no indication of this portion of mine on the underside of leaf. Gallery usually terminates about half-way down leaf, occupying entire width of this half between midrib and margin. Colour of mine very dark brown, lighter around margins; dark green over terminal part while fresh, very dark towards middle owing to frass. “Herring-boning” not very marked. Fresh mines appear somewhat swollen and stand out in relief. Frass black, rather scanty, deposited in a semi-fluid condition on both floor and roof of mine. In the narrow gallery at start it occupies two thin more or less interrupted lines, one on either side of mine, close to margin; this double formation is practically lost in later wider gallery. Never more than one mine found in a leaf. When full-grown, larva makes escape through upper or lower cuticle indiscriminately.

The Pupa. (Figs. 19, 20.)

Pupation normally occurs on or in ground, but not more than ¼ in. below surface. Colour of pupa pale to dark brown. Dorsum rounded; ventral surface almost flat; anterior end directed more ventrad than dorsad, bluntly pointed in lateral profile.

Anterior respiratory processes short, slender, knobbed, almost as far apart as posterior pair, which are stouter with black expanded ends. Seg ments well rounded, shiny, covered with fine annular striae; very fine

and minute spines in intersegmental regions. Posterior ventro-lateral tubercles very prominent, can be seen in dorsal profile. Ventral aperture slightly prominent. Antero-lateral shoulder well pronounced as far back as transverse suture. Dehiscence as in other species already described.

Average measurements: Length, 2–4 mm.; greatest ventro-dorsal diameter, 1·1 mm.; greatest transverse diameter, 1·3 mm.

Average length of pupal existence, three weeks in normal conditions.

(18.) Agromyza citreifemorata n. sp. (The Ngaio-fly).

The Imago.

Male. Frons, palpi, and genae lemon-yellow; antennae orange, arista pubescent, black; ocellar triangle and occiput black; eyes dark blackishbrown; each orbit with four bristles; ocellar and post-vertical bristles of about equal length.

Thorax—dorsum black, faintly shagreened; lateral margins of mesonotum broadly yellow, pleura with sutures and upper margin broadly yellow; four pairs of dorso-central bristles, anterior pair weak; about six irregular series of setulae between dorso-centrals; scutellum bright yellow in central two-fourths.

Abdominal tergites black, with very narrow yellow posterior margins; ventro-lateral areas yellow, under-surface black.

Legs lemon-yellow; tibiae brownish medially.

Wings (fig. 26) clear, veins brown, yellow at their bases; fringes of calyptrae fuscous. Halteres yellow. Last section of fifth vein twice as long as preceding section and four times as long as penultimate section of fourth vein.

Length, 3 mm. Female similar to male, with exception of being slightly larger.

Type in the author's collection; reared from mines obtained in St. John's Hill Reserve, Wanganui.

Distribution.

First discovered in St. John's Hill Reserve, Wanganui, 21st June, 1917, and has been found there every year since. Botanical Gardens and Tomahawk Lagoon, Dunedin (common). Mines have been sent to me by Mr. Tapley from Governor's Bay, Christchurch (scarce). Although widely distributed, by no means common except in restricted localities. Imagines appear in September, November, and January.

Food-plant.

Myoporum laetum (ngaio).

Egg-laying and Larva.

Ova laid singly in small pockets beneath lower cuticle of leaf. Usually three or four pockets, all containing ova, very close together.

Full-grown larva 4 mm., long, pale greenish-yellow, shiny, darker posteriorly; mandibular sclerite has only two teeth in all three instars. Length of pharyngeal skeleton, exclusive of mandibular sclerite—first instar, 0·13 mm.; second instar, 0·24 mm.; third instar, 0·35 mm. Length of mandibular sclerite—first instar, 0·035 mm.; second instar, 0·06 mm.; third instar, 0·09 mm. First moult occurs at a point about 1 cm. from start of mine, second usually within blotch.

The Mine.(Plate 39, fig. 4.)

Disturbing influences being absent, the mine of this fly is a narrow gallery throughout, tortuous in direction, but rarely vermiform—that is, looping closely back and forth upon itself. It is a usual and marked characteristic for several closely adjacent egg-pockets to contain ova of same age, undoubtedly laid by same parent; these hatch together, and larvae tunnel along under upper cuticle of leaf; galleries extremely narrow, black with contained frass, their directions slightly tortuous but practically parallel with one another. At the end of 1 cm. first moult takes place, and galleries then begin to develop short blind branches; these from the several mines meet and intermingle, and so is formed a large irregular blotch. The larvae, however, do not work in common; each strives to maintain its own gallery: the blotch is a fortuitous structure. Frass relatively plentiful, black, semi-viscid. Colour of blotch dark grey-brown in older parts, dark green where fresh, with pale margins.

Mines conspicuous objects on upper sides of leaves; blotches are from 1 sq. cm. and upwards in size. Individual galleries may average 7 cm. in length. Midrib forms no obstacle. “Herring-boning” not as heavily marked as in mines of veronica-flies. Full-grown larvae escape through small slit in upper cuticle. Margins of gallery very irregular. The dry cuticle over blotches soon becomes much wrinkled.

The Pupa. (Figs. 7, 8.)

Leaving mine, larva descends, but does not appear to enter ground. Colour of fresh pupa light yellowish-brown, but within twenty-four hours black. Dorsum evenly rounded; cephalic extremity bluntly pointed; segments narrowing from behind cephalad, not prominently rounded, sculptured with fine annular striae and very slightly hollowed anteriorly in mid-dorsal line. A single row of minute dark-coloured dots between segments. Anterior respiratory processes small, short, and close together; posterior pair large, mushroom-shaped, or prominent tubercles. Antero-lateral shoulders not developed.

Average dimensions: Length, 2·79 mm.; greatest dorso-ventral diameter, 1·17 mm.; greatest transverse diameter, 1·38 mm.

Duration of pupal stage, twenty days and upwards.

(19.) Agromyza clianthi n. sp. (The Clianthus-fly).

Male. Frons, palpi, genae, and proboscis yellow; antennae darker yellow, brownish above; arista black, pubescent; eyes very dark reddish-brown; occiput and ocellar triangle black; each orbit with three strong bristles; ocellar bristles weaker and shorter than the post-verticals.

Thorax dark grey upon dorsum, lateral margin in front of wing-base broadly yellow, pleural sutures yellow; four pairs of dorso-central bristles, anterior two pairs much weaker than posterior, setulae between them long and sparse, arranged in two irregular series; scutellum broadly yellow from base to apex.

Abdomen dark grey above, posterior margins of tergites slightly yellowish; lateral margins yellow.

Legs—femora yellow, brownish near costa; tibiae and tarsi dark brownish-grey.

Wings (fig. 27) pale-greyish, veins black, extreme base yellowish; halteres lemon-yellow; penultimate section of fourth vein one-sixteenth as long as ultimate, and one-ninth as long as ultimate section of fifth.

Length, 1·5 mm. Female similar to but slightly larger than male.

Type in author's collection; bred from mines obtained in Virginia Reserve, Wanganui.

Distribution.

First discovered in Virginia Reserve, Wanganui, in September, 1915, and found there commonly every year since. Has also been found at Heretaunga (Trentham) and Dunedin. Imagines appear to be most common in September, November, and following summer months. Probably three or four generations.

Food-plant.

Clianthus puniceus (parrotsbill, kaka-beak).

Egg-laying and Larva.

Ova laid singly in small pockets constructed beneath under-cuticle of leaf, and usually close to outer margin.

Full-grown larva yellow in colour, shiny, 2 mm. in length. Duration of larval stage probably not longer than two to three weeks. Three stadia. Mandibular sclerite possessing only two teeth.

The Mine.(Plate 38, fig. 2.)

A small simple expanding gallery on upper side of leaf throughout. Width increases gradually from about 0·25 mm. to about 2 mm.; average length, 3–4 cm. Mine as a rule follows margin of leaf more or less closely, being directed first towards apex, and, crossing midrib here, passes on down opposite half of leaf, terminating, after a slightly serpentine course, in vicinity of base. Margins irregular in outline, but blind branches never present. Colour light-green when fresh, white later. Little or no indication of mine on underside of leaf, excepting, of course, the egg-pockets, the majority of which never contain ova. Frass deposited in minute semi-viscid masses, dark-green when fresh, but soon becoming black and clearly showing through transparent cuticle covering mine; deposition of frass very characteristic, occupying two almost parallel interrupted lines of granules increasing in size as mine expands, and occupying central part of gallery; this causes mine to assume a darker tone in centre, with pale margins. Larvae emerge from mine when fully grown, cutting a small semicircular slit through floor of gallery. Two or more larvae may be found mining in same leaf, though as a rule there is but one larva to a leaf.

The Pupa.(Figs. 5, 6.)

Larva pupates amongst vegetation near ground. Pupa differs but little in main features from those already described. Colour pale amber-brown; segments moderately rounded, smooth and shining; on lateral intersegmental regions are a number of microscopic spines; dorsally segments are slightly produced caudad in mid-line.

Average dimensions: Length, 1·93 mm.; greatest ventro-dorsal diameter, 0·86 mm.; greatest transverse diameter, 1 mm.

Duration of pupal existence usually averages twenty to thirty days. Dehiscence occurs as in previous species.

(20.) Agromyza flavopleura n. sp. (The Fern-fly).

The Imago.

Male: Frons, antennae, palpi, proboscis, and genae lemon-yellow; ocellar triangle and occiput black; arista pubescent, black; eyes dark red; each orbit with three bristles and a number of long fine hairs; ocellar bristles weaker than the post-verticals.

Thorax black on dorsum, shining; pleura almost entirely lemon-yellow, two blackish spots, one on sternopleura and a smaller one above hind coxae; scutellum black, except at antero-lateral margins, where it is yellowish, as in adjoining part of thorax; anterior two pairs of dorsocentrals but little shorter than the two posterior pairs; about four irregular series of rather long setulae between dorso-centrals.

Abdomen infuscated except at extreme base, and narrowly at extreme apex of each tergite; under-surface yellowish.

Legs—coxae and femora lemon-yellow, tibiae and tarsi grey-brownish.

Wings (fig. 28) clear, veins dark fuscous, bases yellow; penultimate section of fifth vein over three-fourths as long as ultimate, last section of fourth vein about five times as long as penultimate; halteres yellow.

Length, 3 mm. Female similar to male.

Type in author's collection; reared from mines obtained in Botanical Gardens, Dunedin.

Distribution.

First found at Wellington, in the Botanical Gardens, 19th June, 1919 (fairly plentiful), and has been taken in same locality from time to time since. Found also at Wanganui (scarce) and at Dunedin. Imagines best procured by rearing from mines, and will be found emerging throughout summer months till April.

Food-plants.

Polypodium australe, P. Billardieri, Lomaria filiformis, Asplenium flaccidum.

Egg-laying and Larva.

Ova laid singly in minute pockets constructed beneath under-cuticle of leaves; there appears to be no especially selected part.

Full-grown larva when fully extended 6 mm. in length, just prior to pupating 3·5–4 mm., cylindrical, slightly expanded cephalad in region of third segment; light yellow, shining; mandibular sclerite in each of the three instars with but two teeth; anterior respiratory processes long and slender, about one and a half times the length of the mandibular sclerite. Length of pharyngeal skeleton, exclusive of mandibular sclerite—first instar, 0·19 mm.; second instar, 0·29 mm.; third instar, 0·43 mm. Length of mandibular sclerite—first instar, 0·3 mm.; second instar, 0·07 mm.; third instar, 0·13 mm. Durations of stadia not known.

The Mine.(Plate 39, fig. 3.)

Under favourable conditions, a long, narrow, tortuous gallery. Margins fairly regular. Owing often to narrow fronds, gallery is so much involved as to become in many cases, and especially in A. flaccidum, a blotch covering almost the entire leaflet. Constructed closer against lower cuticle than upper, but just as conspicuous on one side as other. Colour pale green, becoming white, generally slightly discoloured brownish in region of the pupa and at tips of leaflets. Frass dark green to black, very scanty,

irregularly scattered throughout mine, can be easily seen from exterior, and mostly deposited against roof of mine. Gallery may extend into stalks of fronds. In longer and larger leaves of L. filiformis gallery is seen at its best, attaining an average length of 12–18 cm. Frequently several larvae mine in a single leaf.

The Pupa. (Figs. 1, 2.)

Larva pupates within mine in terminal portion. Pupa firmly cemented to roof of mine (occasionally the floor), and dorsal halves of first three and a half segments become flattened to form a definite head-plate, exposed to exterior of mine, a small flap of cuticle being uplifted here. Pupa is flattened dorso-ventrally; greatest diameter about sixth segment; rounded anteriorly; bluntly pointed caudal extremity interrupted by the two tubercles bearing posterior spiracles. Segments barely rounded, of almost equal length, sculptured with remarkably fine annular striae, shiny; a single line of small dark spots between each segment. Hinder segments slightly produced anteriorly in mid-dorsal line; there is, of course, no antero-lateral shoulder. Head-plate bears near extremity the two anterior respiratory processes; these are dark brown, elevated, directed upwards and laterally, each on a distinct tubercle, and they are as far apart as posterior pair; these latter are shorter, directed backwards and downwards, and not expanded at tips, dark brown in colour at tips. Colour of pupa very pale amber, yellowish posteriorly. On dorsum a more or less well-marked median stripe of darker brown, commencing about the next to last segment and gradually expanding cephalad; head-plate light brown with a central stripe of ground-colour.

Average dimensions: Length, 3·24 mm.; dorso-ventral diameter, 0·86 mm.; transverse diameter, 1·21 mm.; length of head-plate, 1 mm.

Average duration of pupal period, twenty-five days. On dehiscence dorsal head-plate, with its respiratory processes, is lifted up, allowing fly to escape; also a slight amount of splitting ventrally around transverse suture.

(21.) Agromyza flavopleura var. casta n. var.

The Imago.

Male differs from preceding species in having no blackish spots on pleura. Length, 3 mm. Female similar to male.

Type in author's collection; reared from mines obtained in Botanical Gardens, Wellington.

Distribution.

First discovered in Wellington Botanical Gardens, 19th June, 1916. Has also been found at Karori, Day's Day, and Petone, but so far not recorded outside environs of Wellington. Imagines emerge September to January, probably throughout summer. Uncommon.

Food-plant.

Asplenium lucidum.

Egg-laying and Larva.

Apparently similar in all respects to A. flavopleura.

The Mine. (Plate 39, fig. 2, and text-figs. 31–34.)

Mine an extremely long narrow conspicuous white gallery, its margins more or less even, blind branches frequent. General course of mine more or less influenced by ribs of leaf. Galleries, usually two or more in a leaf, and extend aimlessly over surface, rarely following outer margin of leaf, and cross each other in all directions, rarely forming a blotch in so doing. Average width of gallery, 1·5–2 mm. Midrib appears to exercise but little influence, cuticle being frequently lifted from it in course of the mine. “Herring-boning” well but not heavily marked. Frass practically negligible, occupying thin broken line along one or other side of gallery. Entire mine close under upper cuticle and little evidence of it on underside. Total length, 15–30 cm. or more.

Fig. 31.—Three complete mines of A. flavopleura var. casta in a leaf of A. lucidum.
Fig. 32.—The work of four young larvae.
Fig. 33.—A single mine, complete.
Fig. 34.—The result of the mining operations of three larvae.

(All tracings from actual specimens; about one-half natural size.)

The Pupa.

Similar to that of A. flavopleura, already described. The following differences occur: Colour, excepting head-plate and spiracles, white; head-plate and anterior respiratory processes entirely dark rich brown, almost black; tips of the tubercles bearing posterior respiratory processes dark brown, the processes themselves white; a very pale yellowish line between each segment; dorsal streak brown and confined to segment immediately behind head-plate, it is expanded and very dark anteriorly. Anterior respiratory processes as far apart as, or farther than, posterior pair, longer and more slender, slightly expanded at their tips.

Average dimensions: Length, 3·38 mm.; greatest ventro-dorsal diameter, 0·68 mm.; greatest transverse diameter, 1·29 mm.; length of head-plate, 0·68 mm.

Dehiscence exactly as in A. flavopleura.

(22.) Phytomyza clematadi n. sp. (The Clematis-fly).

The Imago.

Female. Frons yellow, paler above; ocellar triangle black, ocelli brown; eyes dark red; distal joint of antenna black above, brownish beneath; arista pubescent, black; first two joints of antenna yellow, pedicel obscurely blackish above; proboscis and genae pale lemon-yellow; palpi dark brown, somewhat circular; occiput black; each orbit with four bristles, the lowermost one very weak; between the row of orbital bristles and the eye is a single series of small hairs not extending below third orbital bristle; ocellar and post-vertical bristles strong, the latter almost as strong as inner and outer verticals.

Thorax—dorsum dark greyish-brown, very faint indications of three darker narrow antero-posterior lines; four pairs of strong dorso-central bristles with two or three irregular series of setulae between the two anterior pairs; scutellum dark greyish-brown, bearing four strong bristles; a very narrow lateral line of pale green in front of base of wing; pleural sutures narrowly and obscurely green.

Abdomen dark grey above and below, pale green on sides; narrow bars of pale green between segments.

Legs—first coxae yellowish except for a small area of brown at base; first femora yellowish with obscure brownish darkening towards tibiae; second and third coxae and femora obscurely brownish-yellow; all femero-tibial joints yellow; tibiae and tarsi dark grey, joints yellowish.

Wings (fig. 30) pale-greyish, veins black; bases of wings yellowish; knobs of halteres pale yellow, stems brownish.

Length, 3 mm. Male similar to female, but slightly smaller.

Type in author's collection; reared from mines obtained in bush at Opoho, Dunedin.

Distribution.

Discovered first at Ravensbourne (Dunedin), 12th October, 1919, by Mr. W. G. Howes; since then it has been found to be plentiful throughout the Dunedin district. Has also been found at Heretaunga (Trentham).

Food-plant.

Clematis indivisa (puawananga, pikiarero).

Egg-laying and Larva.

Eggs laid singly in pockets constructed almost invariably beneath lower cuticle of leaves; no apparent preference for any particular part. Pockets not so elaborately made as in P. albiceps, one diagonal thrust of ovipositor into leaf-tissues being apparently all that is necessary. Here also a large number of pockets are constructed, but no eggs deposited therein. Old pockets become very conspicuous on the leaves, both on upper and under surfaces.

Full-grown larva pale green; length, 4 mm. Particulars of stadia not known.

The Mine. (Plate 41, figs. 1, 2.)

A fairly long narrow gallery, averaging 1·5–2 mm. in width. As a rule, all except the final 2 cm. or so lies close beneath upper cuticle of leaf.

Direction of mine tortuous, and in small leaves markedly vermiform; little tendency to formation of branches; margins fairly even and almost parallel. Colour conspicuously white except when covering cuticle is quite fresh, then pale green. Neither veins nor midrib appear to be any barrier to larva at any stage of its existence. Margin of leaf rarely followed closely except for very short distances. At terminal part gallery widens slightly, and within this area larva pupates. Frass scanty, deposited in minute black semi-fluid spots in a single narrow line towards one side of gallery. Very little evidence of mine on underside of leaf. Rarely more than one larva to a leaf. Not only are leaves nearest ground attacked, but also those 15 ft. to 20 ft. up. Average length of mine, about 15 cm.

The Pupa. (Figs. 15, 16.)

Pupa well cemented to floor and roof of mine. The two anterior respiratory processes are thrust through cuticle of leaf to exterior. There appears to be no decided preference for one side of the leaf or the other. Pupa flattened dorso-ventrally, and as viewed from above somewhat ovoid in shape; segments barely rounded, slightly roughened, and shiny, a slight shallow transverse furrow in centre of dorsum of each segment both in front and behind; a single row of minute spots arid several series of microscopic spines in intersegmental regions. Ventral halves of first three and a half segments slightly flattened to form a “head-plate,” and in consequence anterior end of pupa with anterior respiratory processes is directed ventrad; respiratory processes are not here connected with “head-plate,” as in A. flavopleura; they are fairly long and slender, knobbed, fairly close together, and arise from a distinct tubercle. Posterior respiratory processes stouter, about half the length of the anterior, farther apart, and barely expanded at their tips. Colour of pupa dark brown (dark amber in empty puparia), with a darker mid-ventral stripe which widens cephalad and is almost black at anterior end. Anterior respiratory processes black, and posterior ones very dark brown at their tips; head-plate dark brown with an obscurely darker central band. Anal aperture slightly sunken.

Average dimensions: Length, 2·7 mm.; greatest ventro-dorsal diameter, 0·76 mm.; greatest transverse diameter, 1 mm.; length of ventral head-plate, 0·63 mm.

Average duration of pupal existence under normal conditions, thirty days.

On dehiscence the ventral head-plate breaks through cuticle of leaf and allows fly to emerge; also a slight splitting dorsally around transverse suture. Unlike A. flavopleura, where dorsum of pupa is outermost—that is to say, next cuticle through which the anterior respiratory processes are extruded—in both P. clematadi and P. albiceps it is the ventral surface that is outermost.

(23.) Phytomyza albiceps Mg. (The Thistle-fly).

Phytomyza albiceps Mg. : Miller and Watt, Trans. N.Z. Inst., vol. 47, p. 279, 1915.

The commonest and most widely spread leaf-mining fly in New Zealand, its white galleries showing conspicuously in the leaves of the common sow-thistle. It has been identified at the Imperial Bureau of Entomology as P. albiceps, and, as mentioned previously, it is quite possible that it is

the same fly as has been quoted from time to time by T. W. Kirk in the N.Z. Journal of Agriculture. Owing to several inaccuracies in the former paper, it has been found necessary to review it and bring it into line with the present series. The following account entirely supersedes the earlier article.

P. albiceps is attacked by several small hymenopterous parasites, fully 90 per cent, of the larvae perishing from this cause. All the parasites that have emerged in the breeding-jars from this and other leaf-mining hosts are being carefully preserved, with notes on their life-histories, and will be dealt with in a separate paper.

The Imago.

Female. Frons and genae yellowish; ocellar triangle and occiput dark grey; antennae entirely black; arista pubescent; eyes reddish-brown, widely dichoptic; ocelli dark orange; palpi black; proboscis lemon-yellow; each orbit with three strong bristles, and between these and the eye a single series of fine hairs extending the whole length of the front; ocellar and post-vertical bristles about equal, and much weaker than inner and outer verticals.

Thorax dark grey; four pairs of dorso-centrals with rarely any setulae between them, two anterior pairs are weaker than the posterior, and any setulae that may be present are situated between the former. Scutellum dark grey, with four strong bristles.

Abdomen dorsally dark grey with narrow pale-green intersegmental lines; sides pale green; under-surface dark grey with green intersegmental lines.

Legs dark grey to black; femero-tibial joints yellowish.

Wings (fig. 29) colourless, bases yellowish, veins dark grey; halteres pale lemon-yellow.

Length, 2 mm.; wing, 2·5 mm. Male similar to female but slightly smaller—length, 1·5 mm.; wing, 1·75 mm.

Food-plants.

The common sow-thistle (Sonchus asper), also on S. oleraceus and S. arvensis; Scotch thistle; dandelion; nettle; Cape weed (Cryptostemma calendulacea); common groundsel (Senecio vulgaris); Erechtites arguta and E. praenanthoides; dahlia; large cultivated daisy; and possibly also in cineraria, chrysanthemum, marguerite, Melilotus, Noogoora burr.

Distribution.

Apparently common throughout New Zealand; has been found plentifully at Whakamarina, Wanganui, Wellington, Christchurch, and Dunedin.

Ovum, Egg-laying, and Larva.

Ovum cylindrical, pearly-white, glossy, ends rounded; shell very delicate, and devoid of any kind of sculpturing. The micropylar(?) end slightly broader than its nadir.

Length, 0·32 mm.; greatest diameter, 0·15 mm.

The female fly appears to deposit her ova on both surfaces of the leaves of the food-plant. Close observations show that the upper side is almost

invariably preferred, the majority of eggs being laid on the outer margin of the leaf. Having selected a suitable spot for oviposition, the fly lowers her ovipositor till it is at right angles to the surface of the leaf, having to stand on tip-toe for the purpose; with several downward jerks of the abdomen the ovipositor is thrust through the cuticle and pushed beneath its surface, pushing at first directly backwards and later laterally, in this way prising up the cuticle so as to form a minute semicircular pocket in the leaf. After a moment's rest the ovipositor is withdrawn, leaving a single egg within the pocket. Some little time after the cavity has been made the separated cuticle dries, and the whole becomes visible to the naked eye as a minute white spot on the leaf.

While engaged in laying, the fly is very sluggish, and can be closely observed with a magnifying-glass without taking to flight, and can even be gently transferred from one leaf to another; it is, however, extremely rapid of flight. Almost invariably on the withdrawal of the ovipositor from the leaf the fly will immediately turn and eagerly lap the exuding sap. Before continuing the process of laying, the ovipositor and body generally are subjected to a thorough cleansing; all extraneous matter is removed. The egg-laying capacity of any individual probably reaches about 200 ova. The time taken in probing a cavity and depositing the egg rarely exceeds a minute. During the proceedings the back legs are at times violently stamped upon the leaf. Occasionally leaves are found crowded with these pockets, but in such cases only a few of them will contain eggs.

Under normal conditions lava hatches on sixth day after laying of egg, and commences burrowing against upper cuticle of leaf. It passes through three stadia: the first occupies about three days, moult taking place about 1 cm. along mine; second stadium occupies about three days, moult occurring about 4 cm. along mine; third and final stadium occupies about four days, and lava pupates within mine.

Full-grown lava a minute cylindrical grub; cephalic extremity slightly broader than caudal end; colour white, inclining to pale green on account of assimilated food and transparency of skin; head is largely retractile: posterior respiratory processes minute and black, anterior pair white and longer. Average length of full-grown larva, 3 mm.; average diameter, 0·9 mm.

Pharyngeal skeleton fairly strong and black; consists of two similar halves joined cephalad of a narrow cross-bar; each half consists of a long narrow horizontal bar, broadest caudad, and joined at about junction of anterior third and posterior two-thirds of a shorter, more slender, mid-lateral process; anteriorly the mandibular sclerite (also a double process) bears on either half two strong curved teeth. Number of teeth the same in each instar. Average length of pharyngeal skeleton — first instar, 0·13 mm.; second instar, 0·21 mm.; third instar, 0·34 mm.

The Mine. (Plate 39, fig. 1.)

Mine a long narrow gallery, frequently forming an intricate pattern on leaf owing to tortuous course, it and other mines on same leaf crossing each other in grand confusion. Longer or shorter blind branches are frequent. Margins of gallery even and almost parallel. The greater length of mine, as a rule, lies close against upper cuticle, and there is little trace of it on under-surface. In cases where egg has been laid on under-surface the mine will lie close against this for a short distance at first, but sooner or later

comes to lie against upper epidermis. Occasionally, however, a mine may be found altogether on under-surface of leaf. Towards end of third stadium larva forsakes upper side of leaf for lower, and finally pupates within slightly expanded terminal part of mine, the anterior respiratory processes being thrust through lower cuticle to exterior. Pupation seldom takes place on upper side of leaf. Light appears to govern to a great extent the choice of position for pupation; in instances where leaves were placed in the dark the larvae pupated on whatever side of leaf they happened to be mining at the time, whereas in leaves kept in the light the larvae pupated on the side farthest from source of light. Colour of mine white, very conspicuous. Frass black, granular, scanty; granules deposited in a thin interrupted line along one or other side of floor of gallery. Total length of mine averages 15–20 cm., the last 12 cm. or so being constructed during third (final) stadium. Individual leaves may contain eight to ten or more larvae, but these avoid each other as far as possible.

The Pupa. (Figs. 17, 18.)

Pupa somewhat elongated; segments only moderately rounded and tending to be slightly produced caudad in mid-ventral region, each, excepting the four anterior ones, possessing ventrally two short shallow transverse furrows in central line, best marked in middle segments. Anterior end of pupa pointed, and at extreme tip bears the two short slightly knobbed anterior respiratory processes, these being placed-very close together, closer than in P. clematadi.; caudad to these processes, but not including them, ventral portion of first three and a half segments is somewhat flattened to form an ill-defined head-plate, which lifts on dehiscence; in consequence anterior end of pupa is distinctly downturned in dorsal profile, since anterior respiratory processes and head - plate are all on a level with ventral surface of pupa, this surface being outermost as pupa is situated in mine. Posterior extremity bluntly rounded; anal protuberance considerably masks posterior respiratory process when viewed, ventrally; these latter are short and stout, knobbed, and relatively far apart. Anterior processes thrust through cuticle to exterior. Colour of pupa pale amber-brown dorsally, darker ventrally, with broad dark mid-ventral stripe extending whole length; anterior processes rich brown, paler at tips; posterior processes black-tipped.

Average dimensions: Length, 2·45.mm.; greatest ventro-dorsal diameter, 0·83 mm.; greatest transverse diameter, 1 mm.; length of ventral head-plate, 0·5 mm.

Duration of pupal existence under normal conditions, twelve to thirteen days. Dehiscence as in P. clematadi.

Agromyza australensis Mik.

A. australensis Mik., Verh. z.-b. Wien, xxxi, p. 202, pl. xiii, fig. 15, 1881; Hutton, Trans. N.Z. Inst., vol. 33, p. 93, 1901.

“Greyish-brown; the abdomen, in some lights, luminous grey; middle and hind legs pale-tawny. (The fore legs missing.) Posterior cross-vein about twice its length from the chief cross-vein, and about one and a half times its length from the margin.

“Length, 1 ¾ mm.; wing, 2 mm.

“Hab.—Auckland Islands (Dr. Krone).”