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Volume 33, 1900
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Art. XIV.—On Lysiphragma howesii, sp. nov.

[Read before the Philosophical Institute of Canterbury, 4th July, 1900.]

Plate VIII. (in Part).

Larva. (Fig. A.)

Three larvæ received from Mr. G. Howes, of Invercargill, were found by him with others in rotten wood of Plagianthus betulinus, and were contained in rather tough cocoons. The length was respectively ⅜in., ¾in., and ⅞in., and there was no apparent difference in structure, but in the smallest specimen the colour was very pale compared with the larger specimens, especially in respect to the darker structures. My description was made from one of the largest specimens.

Colour: Head dark-brown. Thoracic dorsal plates brown, that of the prothorax paler on anterior edge. Segmental oily white. All tubercles are brown. Legs pale-brown, semi-transparent, not glassy. Hairs pale-brown. Spiracles pale yellowish-brown.

Shape, dorsally: Head broad, smaller than prothorax,

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sloping from base to front, which is produced, and, viewed laterally, snout-like. Thoracic segments are larger than the abdominal, which latter taper gradually to anus. Comparative size of segments twice the width of length; viewed laterally, about the same width as length.

Structure, lateral (under 1 in. objective): Head roughly striated; several dorsal and lateral hairs on lobes; the latter are not hemispherical, but rather square at sides and front. Antennæ have broad basal joints, with a longer joint terminated by a long bristle. The outer maxillary palpus resembles the antennæ, except having no bristle. Spinneret long and slender.

Prothorax: Dorsal plate covers about one-third of lateral area of segment and has one anterior dorsal, one anterior lateral hair, and two hairs, one above other, on posterior area of plate. Below the posterior area of the plate is the spiracle; anterior to the spiracle is a large tubercle with two (? three) hairs; below is a tubercle without hairs, and a large subventral tubercle with two hairs above the legs (in my figure there are three hairs on this tubercle).

Mesothorax: Dorsal plate small at anterior area, produced laterally at posterior; on dorso-anterior area two hairs (one above other). Below the plate is a curious curved tubercle with two hairs (one above other), a large posterior tubercle with one hair, and a small tubercle with one hair, a small tubercle (posterior) without hairs, and a large subventral anterior tubercle with one hair (in my figure there are two hairs on the tubercle); a small anterior subventral tubercle with one hair is sometimes present.

Post-thorax as mesothorax, except the small anterior subventral tubercle is not present. On each pro-, meso-, post-thoracic intersegmental membrane is a single dorso-lateral tubercle, apparently without hairs. The three thoracic segments have legs, each of which has hairs above the joints. The meso-and post-thoracic segments have no spiracles. 1st abdominal segment without feet; anterior trapezoidal dorsal and large, with one hair; posterior trapezoidal tubercle elongate laterally, with one hair situate at the lateral extremity. Below the anterior trapezoidal is a large inverted heart-shaped tubercle with one hair in centre (supraspiracular tubercle); within the curve of the supraspiracular is a minute pale (apparently functionless) spiracle; below are two anterior, two posterior tubercles, each with one hair, and a large subventral tubercle with two hairs. 2 corresponds. 3, 4, 5, 6. have abdominal feet, and correspond as to position of the tubercles, the subventral tubercle, with two hairs, being at base of the abdominal feet. 7, the subventral tubercle has only one hair. 8, the posterior trapezoidals are less remote; supraspiracular is horse-shoe shaped (with one hair in centre),

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and encloses a large spiracle (as on prothorax); subventral tubercle becomes ventral. 9, no spiracle; below the trapezoidals is a large elongate tubercle bearing three hairs, below is a small subventral tubercle with one hair. 10, above the anal flap are three hairs, below is a large tubercle with four hairs, and one hair at base of claspers.

Structure, ventral (under 1in. objective): At the base of each thoracic leg, on the segmental area, is a single hair; on 1 and 2 abdominal are hairs which correspond; 3, 4, 5, 6 have a single hair at the inner side of each of the abdominal feet; 7–10 have hairs which correspond.

Under ¼in. objective: The hooks of abdominal feet turn outwards, forming a complete margin. The skin of the segments is prickly—i.e., densely covered with minute hairs. The setæ, or hairs, of the tubercles are smooth, apparently finely striated.

All the larvæ expired from ill-usage during microscopical examination. My figure was drawn from one specimen, and description taken from another. Subsequently I received another larva from Mr. Howes, which pupated in a frail cocoon amongst moss.

Pupa. (Fig. B.)

Colour: Pale-mahogany.

Length: Exactly ½ in.

Shape and structure (under 1 in. objective): In front of head, above the eyes, is a pointed protuberance; there are two hairs between the eyes; the latter are large, dark, and conspicuous. I am not sure whether there are one or two hairs at base of antennæ. The antennæ and wing-cases extend to the posterior edge of 5th abdominal segment, and are quite separate from and unattached to either 4 or 5 abdominal segments. 4, 5, 6 abdominal segments are free, the remaining segments fused. Pupa tapers rapidly from 7–10, the posterior extremity being terminated by two dorsal and two ventral angular processes, with no trace of hooks or spines.

On all the abdominal segments except 1 and the last two there is an anterior transverse dorsal series of short blunt spines, varying from three rows in middle to one row at extremities of series. These spines extend from spiracle to spiracle, and are terminated at or by a single hair (homologous of the supraspiracular hair). The spiracles are very like those of the larva—small, round, and elevated. Below the spiracle is a minute hair, and posterior to it is another. Abdominal segments 3 to 6 have a second series of spines—a single posterior row, and not so numerous as the anterior series. Among the spines of the anterior series are hairs possibly analogous to the anterior trapezoidals of the larval

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stage, but I cannot find traces of the posterior hairs. The ventral area of pupal segments is smooth (no spines), with some hairs possibly homologous of the subventral and ventral larval hairs.

This pupa met with an accident during examination and succumbed. However, I had the satisfaction of receiving a note from Mr. Howes, saying he had bred a specimen of the imago. Upon this I wrote, asking him to forward empty pupa-case, so that I could examine the manner of dehiscence, and I subsequently received same. The dorsum of metathorax is split centrally. Prothorax, head parts—antennæ, proboscis—and leg-cases separate from each other and from the wing-cases throughout their length; the latter remain connected with the thoracic segments, but are quite severed from the abdominal segments.

Mr. G. Howes was also kind enough to forward specimens of the imago to me, same having been bred on and after the 21st December, 1899.

Imago.

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Expands 13/16in. The markings of wings are not very distinct. Ground-colour of fore wings is greenish, intermixed with paler scales; near the base is a suffused blackish line. At ⅓ on the inner margin is a black spot, at ½ a similar spot; both extend upwards by a thin wavy line to about the middle of wing. On the costal margin at ⅔ is a light patch edged with black; at the apex there is also a light patch. The costa is marked with black dots. Hind wings are grey on basal area, darker at margin. Thorax silvery, with green scales intermixed. Abdomen silvery-grey.

Structure: Antennæ comparatively long; clavola segments elongate, with a broad margin of basal scales, directed anteriorly. The labial palpi are large, ascending, each joint covered with scales. Maxillary palpi are long and slender, with several joints covered with scales; there is apparently a short proboscis.

Neuration (Fig. C): Fore—Subcostal, 1; radius, 5; media, 3; cubitus, 2; anal, 2 = 13 nervules. Hind—Subcostal, 1; radius, 1; media, 3; cubitus, 2; anal, 1 = 8 nervules.

The neuration is distinctly specialised—that is to say, very much modified from assumed (Trichoptera) lepidopterous primitive type. The loss of the stem (nervure) of the median system is itself a mark of specialisation, although the median of the hind wings remains. The number of radial nervules (hind) is reduced to one only. It would be interesting to compare this neuration with that ofSesiidæ (New Zealand) representative, S. tipuliformis, introduced from Europe),

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which, so far as my memory serves me, is a further specialisation of a similar type.

Wing-scales: Towards the base of the inner margin of fore wings I observed some hairs and a few scales without teeth (fig. 1). On the wing-surface are three types of scales—broad with blunt dentation, broad with sharp dentation, long narrow scales irregularly dentate; the latter appear to be associated in position with the nervures on the wing (figs. 2, 3, and 4). Towards the outer margin I only observed the broad scale with sharp dentation (fig. 3). The fringe is composed of two patterns of scales: one forms a narrow fringe of scales longer than the surface scales, broad at outer end and more deeply dentate (fig. 6); one pattern forms a broad fringe of longer, attenuated scales, the broad end split into very long teeth (fig. 5). Both these patterns are contained in the fringes of fore and hind wings, and they rise from the edge of the wing-membrane.

The study of scale-structure seems to be usually neglected, yet appears to me worthy of attention. Among Lepidoptera of more ancient type—for instance, Hepialidæ —the thorax, legs, and abdomen are covered with hair, and the covering of the wings is partly hair, partly—towards the margins—scales. These scales have smooth (rounded somewhat) tips among ancient genera (instance Porina), dentate tips among specialised genera (instance Hectomanes, of Australia), and, though the majority of Lepidoptera appear to have dentate wing-scales, and scales on the thorax, &c, the study of their structure would appear to be of value as an indication of affinity.

Mr. Howes also kindly sent me specimens of Lysiphragma epyxila, * imago, the larvæ of which he states have similar habits, and feed on the “soft inner bark of the broadleaf-tree.” This species, as regards neuration and wing-scales and antennæ, is also identical with that which forms the subject of my paper. It is, however, a larger insect. The markings are similar, and evidently the two are most closely allied.

Explanation Of Plate VIII. (In Part).

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Imago of Lysiphragma howesii, nat. size.
Fig. A Larva of Lysiphragma howesii; enlarged about 4 by 4.
Fig. B. Pupa of Lysiphragma howesii; enlarged about 4 by 4.
Fig. C. Neuration of wings; enlarged about 50 diameters.
Fig. 1. Basal wing-scale enlarged about 200 diameters.
Fig. 2. Surface wing-scale
Fig. 3. Surface wing-scale
Fig. 4. Surface wing-scale
Fig. 5. Outer-fringe scale
Fig. 6. Inner-fringe scale

[Footnote] * Meyrick, Trans. N.Z. Inst., vol. xx., p. 105 (1888).