Art. XXV.—Embryology of New Zealand Lepidoptera: Part II.
[Read before the Philosophical Institute of Canterbury, 11th February, 1902.]
Plate XIII. (See also pl. ix., vol. xxxiii.)
Embryology in interest supersedes the pleasures of collecting and preserving specimens in the imago stage, and enhances the scientific value of the Lepidoptera in entomology. Breeding insects is a means towards an end—good specimens to the collector. On the other hand, the desire of the student is to know what can be learnt of structure, habits, and so forth. I know prominent embryologists in England who, after devoting great attention to breeding and hybridizing species, hand over the resulting imagines to some collector friends.
Probably most collectors would at once kill and set a female specimen of any scarce or rare species, if in perfect condition, but an embryological student would almost certainly try and procure ova. Such a case I well remember. A party of several entomologists were at the New Forest, England, and my friend Mr. Arthur Bacot took a freshly emerged female of a scarce species—Peridea trepida, I think—which he decided to keep until night and try to assemble some males. Any other of the party would have killed it at once, on the principle of “a bird in the hand is worth two in the bush.” That evening, before sugar commenced, we hung her ladyship like a songster in a cage, from a branch of
a tree. Later on she caused an assembly of the opposite sex of her species, and as they hurried up we could see their little eyes glow in the darkness quite a distance away. They would fly straight to the cage and crawl all over the gauze sides, and the light from our lantern did not scare them. As they flew up we netted them, until quite a number of males had been taken; and when the flight was over one was let in do the cage, when it immediately copulated and fertile ova resulted. The captured males were handed over to the other entomologists present.
For the purpose of embryology and of classification it is necessary to describe the pattern of the ovum, the structure of the larva and pupa. Although we may not know the why or the wherefore, there must be some functional, constitutional, or environmental reason for such structures. Without further preface I will now offer for your consideration such observations on some species of New Zealand Lepidoptera as my limited time has permitted.
A Contribution to the Life-history of Metacrias (Meyr.)
For my material I am indebted to Mr. George Howes, who recorded the occurrence of this species at Invercargill.* The apterous female of this and of the two congeneric, species raises the interesting problem of the cause of such a condition. The Arctid genus Ocnogyna, of Europe, has females with rudimentary wings, but I know of no others in the group. Laparidæ, which by derivation must have more or less remote affinities with Arctids, have some completely apterous females, some with rudimentary wings. Other groups of Lepidoptera not associated with these exhibit the same phenomena. Such must be considered specialised, and the apterous condition of the female is intimately associated with reproduction. Lessen productivity and the species is nearer extinction. Whether specialisation of the ovum and its chemical contents is the great factor in reduction of productivity can hardly be proved, but I am inclined to think it is so. The organism, after exclusion from the egg, builds up physiologically from matter assimilated as food; but before exclusion from the egg the organism is formed entirely from matter contained within the egg, derived wholly from the female parent (granted seminal stimulus of the male) by the primary unicellular germ using up surrounding cells in the ovary of the parent until the ovum developed. This, at least, is as I understand the process. The quantity of cellular matter absorbed per ovum would affect the quantity of ova resulting; specialisation
[Footnote] * Trans. N.Z. Inst., vol. xxxiii.
no doubt would cause greater absorption, and consequent reduction, in number of ova. This might be partially counteracted by conversion of energy towards the formation of cellular matter in the ovary at the expense of imaginal structures, until, as in Metacrias, the female becomes a helpless ova-bag.
In his letters Mr. Howes tells me that a male M. strategica copulated with three separate females in the course of perhaps twenty-four hours. It is interesting to get authentic records of such. Many entomologists believe the males among Lepidoptera only pair once I have no doubt male M. strategica would assemble to a virgin female if exposed at the proper time of flight and in a suitable locality.
Deposited, 4th November, 1900; hatched, 27th November, 1900–23 days. Spherical in shape; pale honey-colour; eggshell apparently exceedingly thin, with irregular hexagons over its surface, more distinct than on Nyctemera annulata. It may here be noted that I have examined batches of N. annulata ova which were quite smooth, others having a faint hexagonal pattern. Mr. Howes mentions that the young newly hatched larvæ eat the eggshell. This is done by N. annulata.*
Larva. (Plate XIII., fig. 8; vol. xxxiii., pl. ix., fig. 18.)
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Newly hatched.—Robust; all the segments approximately uniform except head, prothorax, and the two posterior abdominal segments, which are smaller than the others. Tubercles are crowded together and give the larva a rather dark colour, though the skin is yellowish-brown. The head, scutellum, dorsal anal shield, and tubercles are brown; the setæ are black. The setæ are spinulose, and the skin is covered with minute (secondary) hairs. At first the head appears to be larger than prothorax, but, enclosed in its chitinous envelope, it does not grow, and prior to ecdysis the prothorax is larger than the head. The dorsal and lateral multisetiferous tubercles are at first prominent elevations on all the segments, but when the skin is fully distended prior to ecdysis the dorsal tubercles of 9th abdominal segment only appear to be specially prominent. When full fed in first skin the length is 3/16 in., and there is a slight reddish mottling on the skin.
Head: The ocelli are crescentic; the numerous hairs are spinulose.
Prothorax: Dorsal shield has on each side of the median
[Footnote] * Entom., vol. xxxiv., p. 141.
line three anterior marginal setæ and two posterior setæ. Supraspiracular and prespiracular tubercles each have three setæ. The spiracle is circular in shape, and posterior. A tubercle above the legs has two setæ.
Meso- and post-thoracic segments: Trapezoidal tubercles appear to be coalesced, forming large dorsal tubercles with about six setæ. Supraspiracular has about eight setæ, slightly below which a small posterior (subspiracular) tubercle has a single very fine seta; a larger anterior subspiracular tubercle has a single seta. Tubercles above the legs have two setæ.
The thoracic legs have spinulose hairs, and terminate with a long claw, a rudimentary claw, and a flattened seta, to which Dr. Chapman gives the name “battledore palpus” in describing Arctia caia.*
Abdominal segments (vol. xxxiii., pl. ix., fig. 18): Anterior trapezoidal tubercle has three setæ, posterior, trapezoidal one seta. Supraspiracular tubercle is anterior above the small circular spiracle, and has about seven setæ. One subspiracular tubercle is below the spiracle, but posterior to it, with one seta, and almost beneath this, but a little anterior, is another, with a single seta, and still lower a tubercle-like area without seta. On the base of abdominal feet are one spinulose seta, one smooth seta; on the footless segments 1 and 2 these rise from a subventral tubercle and are both spinulose; the subventral tubercle of segments 7 and 8 have only one seta (spinulose). Segment 9 has a very large dorsal multi-setiferous tubercle, one lateral, one subventral, each with only one seta. Segment 10 has a dorsal multisetiferous tubercle, a lateral spinulose seta, and some setæ on claspers; also on each side of the anal orifice a single smooth seta curved upwards. On all the segments one sefa of each supraspiracular tubercle is about twice the length of any other. Mr. Howes mentions the presence of several long grey hairs from the anal extremity. This is a very striking feature, and persists, I believe, until the larva is full fed. These hairs are actually the post-trapezoidal setæ of abdominal segments 7 and 8, which are about four or five times the normal length, are spinulose throughout, and greyish beyond.
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Second Skin.—Length immediately after ecdysis 3/16 in. The tubercles, being more setiferous, are larger, and form very prominent elevations on all segments. The skin is yellowish-brown, the setæ brown and spinulose
Head has spinulose setæ, but not noticeably more numerous than in first stage.
[Footnote] * Ento. Record, vol. 4, p. 267.
Prothorax: Dorsal tubercle very prominent, having about a dozen anterior and two posterior setæ on each side. Supra-spiracular tubercle about three setæ, prespiracular about ten setæ; spiracle posterior; tubercle above leg has about ten setæ.
Meso- and post-thorax: The dorsal tubercles (medio) appear to be coalesced, and are exceedingly setiferous. A subdorsal and two other tubercles are one below another, with about ten to fourteen setæ each; a smaller tubercle, slightly anterior, above the legs bears three or four setæ. Above the subdorsal tubercle is a small posterior tubercle with one seta.
The thoracic legs terminate as in the preceding stage.
Abdominal segments: Anterior trapezoidal about a quarter the size of posterior, and bears three setæ; post trapezoidal bear ten setæ. Supraspiracular is midlateral, bearing about fourteen setæ. The spiracle is immediately anterior to the uppermost seta of the post subspiracular tubercle, which bears about ten setæ. Immediately below this the other subspiracular hears the same number of setæ, and below this a small tubercle bears three setæ. The abdominal feet bear several single setæ.
The numerous setæ render it extremely difficult to make a description which is absolutely accurate. The larva lived until about three-quarter grown, and I did not observe any further structural difference. The setæ throughout were brown, but the subspiracular setæ were lighter brown than the dorsal setæ. Mr. Howes states that the larva, when full fed, is 1 ¼ length.
Pupa. (Plate XIII., figs. 9, 10.)
The pupa is enclosed in an oval cocoon of coarse silk threads interwoven with larval setæ. The cocoon is rather dark-brown in colour, and the enclosed pupa can be seen through it.
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Male pupa: Length, about 5/3 in.; at widest, ¼ in. Colour very dark-brown, with paler incisions. Wing-cases extend to the middle of 4th abdominal segment ventrally. Abdominal segments 5 and 6 are free; 7, 8, 9, 10 are consolidated and lessen rapidly, forming a rounded extremity with a rather sharp terminal process. The anal armature consists of about twelve stout bristles, with innumerable sharp points at their clubbed end (fig. 10). The anal armature of Nyctemera annulata (fig. 11) consists of numerous hooks, not straight bristles, and under a high power these are seen to be ball-tipped, resembling closely the anal armature of some Noctuæ (fig. 7, Melanchra mutans). In the position of larval tubercles numerous rudimentary setæ, pale yellowish-brown in
colour, resemble the longitudinal yellow spots on the pupa of Nyctemera annulata. On dehiscence the wing-cases separate from the ventral juncture and along the sides of the abdominal segments to the suture with thoracic segments, which separate mid-dorsally, and remain attached to either wing-case. The face, antennæ, and leg-cases remain welded together, but separate from the wing-cases almost to the juncture of the 5th abdominal segment.
Female pupa about the same length as male, but extremely robust in comparison. It tapers sharply from the 3rd abdominal segment to head, dorsally and laterally; 4, 5, 6 appear to be wholly free segments, and are the widest—fully 5/16 in.; 7, 8, 9, 10 are consolidated and form on extremity, with armature similar to the male. Small wing-cases extend to the posterior edge of 3rd abdominal segment, and abdominal rudimentary setæ correspond to the male. The head also is covered with numerous similar setæ.
Duration of pupal existence, about twenty days.
[Since my paper was written I received from Mr. George Howes several larvæ of Metacrias strategica, which, after very little feeding, pupated in the usual cocoons amongst moss or grass, and subsequently produced several male and female imagines. I may say, so far as colouration or size is concerned, there appeared to be no difference between the several larvæ such as might be interpreted as an indication of sex. Owing to the fact that the female did not leave its cocoon, I was unaware of it for at least several days, when it appeared to me to be dead, but had already deposited several ova—pale-yellow colour, with distinct hexagonal sculpture. On emergence the female entirely ruptured the pupa-case at every suture, and only remnants remained intact. The female certainly deposits its ova in a normal and proper manner amongst the wool which lines the cocoon. This wool (hair-like scales) acts as an envelope, possibly incubator, for the ova, in the manner observed amongst Psychidæ.* M. strategical however, has wool all over its body; but at the time of my examination this had been almost entirely rubbed off, except from the two or three posterior segments. Probably when the burden of ova has been disposed of the empty female M. strategica crawls out of the cocoon, as is the case with Psychidæ. In my previous remarks I was under the impression that the female M. strategica was entirely apterous. This is not strictly so, as there are rudiments of both fore and hind wings, though so small as to be entirely functionless. The several organs of the caput are better developed than are those of the female (Oeketicus omnivorus, which latter, has,
[Footnote] * Dr. Chapman, Trans. Ent. Soc., Lond., 1900, 403.
however, a greater capacity for the production of ova as regards quantity. With regard to assembling males of M. strategica, I have received a note to the effect that Mr. Philpott, of Invercargill, was successful in taking a large number by exhibiting virgin females. No doubt similar results would be obtained with other species of this genus.]
A Contribution to the Life-history of Melanchra (Hb.)
Ovum. (Plate XIII., figs. 1, 2, 3, 4.)
A batch of ova was found on the 14th April, 1901, which hatched on the 19th April, 1901. The parent female had pushed them between a blade and stem of withered grass, where they were effectually hidden. The ova were laid in two parallel rows of six each, three others separate, and two rows of three each were laid on top of the first; total number, twenty-one.
Ova: Dull to the naked eye, shining under the microscope Colour, pale-whitish, upper half irregularly coloured a dirty brown. Shape, a flattened sphere—i.e., wider at equator than in vertical section. Micropyle at top with irregular hexagons, from which strong corrugations diverge towards the equator, converging below. About one in three of the corrugations coalesce with another at the shoulder of the egg, and there is irregularity in this respect: in more than one instance three corrugations coalesce. About twenty-one corrugations meet the micropylar depression. Between the corrugations equidistant finer lines apparently form four-sided figures, but, examined with a higher power, it is found they are really modified hexagons, with strong longitudinal sides. The evolution of parallel ribs on specialised ova from more primitive hexagonal forms is here clearly evidenced.
The contents of a female abdomen were microscopically examined. Within the abdomen the ova are pale-green in colour, placed end on end, pressed flat against each other, so forming continuous rouleaux of ova, from which each ovum is easily separable. This fact is due to the absence of connecting-tissue such as envelopes the ova of Hepiah within the abdomen.
The exact process is, necessarily, not easy to detect, but I was fully satisfied that the rouleaux of ova are bathed lengthwise by a fluid (fat?). So long as this continues the ova are smooth, but as activity decreases and the quantity of fluid diminishes on exposure to the air sculpturing appears on the eggshell. When quite dry the ova have the orthodox sculpture of deposited ova.
That the sculpture is due to the fluid is nearly certain—
i.e., in the process of drying it forms into natural crystalline shapes. of course, this crystalline formation would occur so rapidly on deposition of the ova that it would be difficult, if not impossible, to detect. It is probable, however, that the bathing of the ova continues until the ovum is excluded from the oviduct.
At the top of the egg-mass, where the incision would be first made, a few ova remained smooth when dry. This detracts nothing from the foregoing, as I conclude that these, being earliest exposed to air, were insufficiently bathed by the necessary sculpture-producing fluid.
The results of this examination justify the conclusions suggested by the experiments of Messrs. Woodhead and Dawson, to which I refer in Part I. of this paper.
Larva. (Plate XIII., figs. 5, 6.)
The first meal consists of the empty eggshell, and, though frequently disturbed so that the larvæ moved away or dropped by a thread, they invariably returned and recommenced feeding on the eggshells.
Newly hatched.—Robust, slightly tapering towards posterior; head large and long, tubercles prominent, setæ long and widened at tip. The first two pairs of abdominal feet are small, that of segment 3 being little more than large tubercles provided with hooks. Neither pair of segments 3 and 4 seems to be used, so the larva in walking progresses in semi-looper manner (fig. 5). Colour, reddish. Skin smooth.
Head: Setæ pointed, mandibles serrate.
Prothorax: Scutellum bears on each side two separate anterior and two posterior setæ. Supraspiracular tubercle bears two setæ; prespiracular two setæ (?); tubercle above legs two setæ. Meso- and post - thorax, three single-seta tubercles, one below the other; one anterior and one posterior lower each with one seta.
Abdominal segments: All the tubercles bear a single seta. Trapezoidals normal. Supraspiracular beneath the anterior trapezoidal and above the round spiracle, immediately posterior to which is one subspiracular tubercle, and below the spiracle is the other. The abdominal feet bear two single-pointed setæ, which are subventral on segments 1 and 2. On segments 7, 8, and 9 there seems to be only one subventral seta each; segment 10 has all pointed setæ. Two subdorsal posterior, curved downward, two posterior, curved upward, and two on each of the claspers.
On the 1st May some of the larvæ had changed to second and some to third skins.
Second Skin.—Colour, pale-green, head pale - brown;
tubercles, setæ, and spiracles brown; faint pale spiracular line, the skin above being really darker than below. Anterior segments darker than posterior.
Structure: Prothorax (fig. 6) apparently as in first stage. Meso- and post-thorax have an additional tubercle. Careful comparison of first and second stages induces me to think this is not the one immediately above the leg, but the posterior tubercle above it in position. Abdominal segments also have an additional tubercle above the legs in a posterior position. The posterior subspiracular tubercle appears to be rather lower down in relation to the spiracle than in the first stage. The abdominal feet bear three pointed setæ; the first two pairs are larger than in first stage.
In succeeding changes of skin the abdominal feet gradually become normal. This, I think, takes place not earlier than the fourth skin, but I have no note on this point. Adult markings are also gradually assumed. In that skin preceding the last, two larvæ confined in the same pot of grass assumed entirely different plumage as regards colour, one being wholly green, the other brown (this was probably green, more or less, ventrally, but I omitted to note). This striking difference is not unusual amongst Noctuæ larvæ, and appears to be attributable to environmental causes. One at least frequently rested during the day-time on the reddish earthenware pot. In a state of nature they rest on the earth, or on a stem of food near the earth. The exciting cause of the variation may be considered to depend on whether the larva rests habitually on the earth or on the stem. In the former case we might expect them to assume a brown colouration, in the latter green, each being to respective individuals equally protective during the period of rest from feeding.
Immediately preceding pupation the length is about 1 in.; colour above spiracular line reddish-brown, below pale-green (the larva mentioned above lost its green colour at last ecdysis). A rather indistinct medio-dorsal line is marked more distinctly at the incisions as a brown spot. Thin dark sub-dorsal line is edged with lighter, and very distinct dark spiracular spots on all the segments. In preceding stage these were oblique dashes. The clypeus of head is dark-brown, middle of lobes a dark streak, edges dark-brown. Under the microscope the larva-skin is mottled, and the pattern of markings not apparent. No doubt the larva is more inconspicuous to small foes than to our eyes, which take the whole form and markings at one comprehensive glance. Even so, to us the larva seems wonderfully protected by its colouration when at rest.
I omitted to note the exact duration of larval existence.
Pupa. (Plate XIII., fig. 7.)
Colour, reddish - brown; length, 9/16 in.; widest at 4th abdominal segment. Wing-cases extend to posterior ridge of 4th abdominal ventrally; hind-wing margins show laterally from post-thorax to anterior edge of 4th abdominal. On dehiscence the headpiece, leg-covers, antennæ, and proboscis-covers remain intact, but separate throughout their length from the wing-cases. Spiracles are transverse and fully developed on 2nd to 8th abdominal segments; on 2nd and 3rd the position is subdorsal, on others normal. Posterior edges of 4th, 5th, and 6th abdominal segments form prominent ridges; the other segments are smooth and taper gradually to the 10th viewed laterally and dorsally, but ventrally the 10th is depressed suddenly from the suture to anal armature.
The anal armature is more especially a dorsal apparatus, though the two strong hooks are terminal processes. On the dorsum there are two pairs of weaker hooks. Somewhere I believe I have seen a statement of Dr. Chapman in which he says that the more he studied the structure of the pupal anal armature the less value it seemed to be. With this species and M. composita (vol. xxxiii., pl. ix., fig. 21) there is decided affinity in the anal armature, which in both consists of six hooks, yet there is abundant specific distinction.
The moths emerged about the 10th September, 1901.
A Contribution to the Life-history of Asaphodes (Meyr.)
Ovum. (Vol. xxxiii, pl. ix., fig. 4.)
Colour, pale-green when laid, partly reddish to the naked eye, but salmon-colour under microscope in two days. Shape is longer then broad, small end rounded, broad end rather fiat, transverse section almost circular. The whole shell is covered with hexagonal cells. The ovum is laid on its side. The larva emerges at the broader end.
Deposited on the 2nd December, 1900; hatched on the 16th December, 1900—fourteen days.
The young larvæ do not eat the empty eggshell.
Larva. (Vol. xxxiii., pl. ix., figs. 5, 6, 7, 8.)
Newly hatched.—Colour, pale yellowish - brown. The thoracic segments have thin red longitudinal lines; the incisions between abdominal segments 1 to 7 are ringed with red all round. The abdominal segments also have yellow spiracular and subspiracular lines running through the red rings.
The larva is robust, with uniform segments, but 7, 8, 9, and 10 are very crowded. The thoracic segments have legs;
the abdominal feet are midway between the 6th and 7th segments, and 10 has claspers.
The arrangement of the thoracic segments is not quite clear, but appears to agree with the structure in the second skin. The head has pointed hairs.
The abdominal tubercles have single setæ, which are club-tipped. Owing to the robust build of the segments the tubercles are very wide apart. The trapezoidals are normal. Supraspiracular and anterior subspiracular are both anterior to the spiracle and equidistant; post-spiracular moved up close to the spiracle. There are anterior and posterior sub-ventral tubercles. The setæ on the abdominal feet are pointed. The larva-skin appears to be covered with very fine hairs.
Second Skin.—Larva attenuated, tubercles still widely separated. Head yellowish, spotted with red. From prothorax to anal segment yellow and red lines alternate longitudinally.
Head: Anterior hairs are pointed, posterior clubbed.
Prothorax: On each side of the thin median line of scutellum there are two anterior, two posterior, equidistant setæ. The prespiracular tubercle has a single seta. Above the spiracle, close to the scutellum, a very fine seta. The spiracle is posterior. Prespiracular tubercle has a single seta. Tubercle above the legs has two separate setæ.
Meso- and post-thorax: Close to the median line a minute normal tubercle bears a single seta, below this a larger tubercle and another (subdorsal); anterior, and posterior tubercles are equidistant from the subdorsals beneath; the tubercle above legs bears one seta. All the tubercles bear only a single seta.
Abdominal segments have an additional tubercle below the spiracle. The spiracle is level with the posterior subspiracular tubercle. On the abdominal feet there are seven single setæ, and numerous setæ on claspers. Abdominal 9 has all the tubercles on the posterior edge; 10 has, above the anal orifice, two normal setæ, two pointed setæ on each side.
Full fed (30th January, 1901).—Length, 9/16 in., wider at 5th abdominal, from which it tapers to head and to anus.
Colour: Brown, with mediodorsal pale line on the thoracic segments, represented on abdominals 1 to 5 by an inverted V—apex anterior, and line resumed but wider on the posterior subsegments of 6 to 9. The posterior trapezoidal setæ of 6th and 7th abdominals are on elevated humps; segment 8 has pale-coloured humps; 9 also has pale humps, but with a larger hump between them.
Laterally there is no definite marking, the whole skin being finely mottled brown and whitish. The setæ are all very
dark—black(?). The tubercle arrangement appears to exactly correspond with second skin.
In an earlier stage there is a lateral subspiracular and spiracular line in addition to the dorsal markings. The skin also has numerous white dots.
A slight cocoon is made on the top of earth.
On the 6th February, 1901, all had pupated.
Pupa. (Vol. xxxiii., pl. ix., fig. 22.)
Colour: Reddish; antennæ, leg-covers, &c., pale-brown, eye-covers dark-brown, wing-covers brown.
Length, 5/16 in. From tip of head to tip of wing-cases is fully two-thirds total length of pupa, the posterior third constituting abdominal segments 5 to 10. Pupa is thickest; at 1st, 2nd, and 3rd abdominals, and there is sharp irregular tapering from 7 to 10; 9 appears as a large swollen area overlying 10, which fits into it as if it were a cap, and terminates with two lateral, two central, hooks, with which a very firm hold is taken of the silk in the cocoon.
The eye-covers are large and prominent; antennæ extend to tips of wing-cases, enclosing legs and proboscis, which also extends to the tips of wing-cases.
Only the slightest portion of the base of hind-wing cases can be seen at the juncture with post-thorax. Spiracles on 1, 2, and 3 are subdorsal, 4 to 8 lateral. All the segments except 8 to 10 are deeply pitted.
Imagines emerged as follows: On the 25th February, a male; on the 26th February, a male and a female; on the 28th February, a male; on the 2nd March, a male; and on the 4th March, a female.
It is not my intention to discuss imaginal structures; indeed, this would not be in keeping with the title of my paper. What I have to say is rather in the nature of inquiry.
The larval antenna consists of a base, one or two joints, and appendages of a fleshy nature (Plate XIII., fig. 12). The imaginal antenna consists of scape (base), pedicel (2nd segment), and clavola (segments beyond). The scape is the muscular base and the pedicel is the nervous base, these being more or less simple in external structure (fig. 13). The clavola segments of A. megaspilata, male, have paired appendages attached to the shaft ventrally, and on this surface the segments are devoid of scales; dorsally the shaft is thickly protected with scales (figs. 14 and 15). The pectinations have no scales, but numerous fine hairs. The clavola segments act as sense-conductors.
The functions of the larval and imaginal antennæ are no doubt similar, and the homology of their respective parts should prove an interesting study. That such is possible is
suggested by the experiments of Dr. Chapman* on regeneration of the thoracic legs of Liparis dispar, which prove the homology of the larval and imaginal legs.
The marginal wing-bristles admit of further study (fig. 16). My note on those of Melanippe fluctuata† was, I understand, the first publication in England in reference to these. Dr. Chapman‡ has dealt with the same, but I have not yet seen his paper on the subject. Messrs. Furbush and Fernald had previously published observations on these structures in America. They are to be observed at the termination of the nervures, but are not of the nervures, since they occur at the wing-margin between the nervures. Professor Fernald believes they are found on the wings of all Lepidoptera. The function of the marginal wing-bristle is unknown.
Explanation of Plate XIII.
Fig. 1. Melanchra mutans, micropylar area of ovum; x 200.
Fig. 2. " longitudinal ribs of ovum; x 200.
Fig. 3. " ovum; x 50.
Fig. 4. " ova from female abdomen; x 50.
Fig. 5. " larva, first skin, showing the imperfect development of abdominal feet.
Fig. 6. " larva, second skin, thoracic segments; x 200.
Fig. 7. " pupa, terminal armature; x 50.
Fig. 8. Metacrias strategica, larva, first skin, thoracic segments; x 200.
Fig. 9. " pupa, segments 5 to 10; x 50.
Fig. 10. " pupa, anal bristle; x 200.
Fig. 11. Nyctemera annulata, pupa, anal bristle; x 200.
Fig. 12. Asaphodes megaspilata, antenna of larva.
Fig. 13. " antenna of imago, scape, pedicel, first clavola segments; x 200.
Fig. 14. " antenna of imago, terminal clavola segments; x 200.
Fig. 15. " intermediate clavola segments; x 200.
Fig. 16. " marginal wing-bristles; x 200.
[Footnote] * Entom. Record, vol. xii., 141.
[Footnote] † Entom., vol. xxxiv., 47.
[Footnote] ‡ “Some Wing-structures,” Trans. South London Nat. Hist. Society, 1900.