Art. VIII.—Illustrated Life-histories of New Zealand Insects: No. 1.
[Read before the Wellington Philosophical Society, 3rd December, 1919; received by Editor, 9th December, 1919; issued separately, 4th June, 1920.]
The present article is the first of a series I hope to publish from time to time on the life-histories of New Zealand insects, which to the best of my belief have not previously been recorded. The subjects will not be selected in any systematic order, but the life-histories will simply appear as they are worked out in the field. Preference will, however, be given to those orders of insects where the least is known regarding their habits, and the species dealt with will therefore mainly belong to the so-called “neglected orders.” Hence species belonging to the better-known orders of Lepidoptera and Coleoptera will be excluded from the scope of these papers at present. Illustrations will be given with each paper, which it is hoped will enable any naturalist to recognize the insects in all their stages. Such structural descriptions as may be given will be extremely brief, as it will necessarily devolve on specialists in each order to give fuller details when the study of the “neglected orders” is taken up in real earnest. In the meantime the present notes and illustrations may be useful in arousing interest and in presenting the subject in an intelligible form to the general student of nature.
Gnophomyia rufa. (Plate I, fig. 7. ♂.)
Tipula rufa Huds., Trans. N.Z. Inst., vol. 27, p. 294. Gnophomyia rufa Hutton, ib., vol. 32, p. 39.
This large and very handsome species of crane-fly, or “daddy-long-legs,” may be found occasionally in dense forests in the Wellington and Nelson districts. It is very possibly a generally distributed species, but precise
Fig. 1.—Limnophila sinistra ♂. Nat. size.
Fig. 2.—Pupa of L. sinistra. Magnified.
Fig. 3.—Larva of L. sinislra. Magnified.
Fig. 4.—Larva of Melanostoma decessum. Magnified.
Fig. 5.—Melanostoma decessum. ♂. Magnified.
Fig. 6.—Pupa of M. decessum. Magnified.
Fig. 7.—Gnophomyia rufa. ♂. Nat. size.
Fig. 8.—Larva of G. rufa. Magnified.
Fig. 9.—Pupa of G. rufa. Magnified.
records of its distribution are at present lacking. The larva lives and feeds in the semi-liquid vegetable detritus which accumulates in large quantities at the bases of the leaves of the well-known Astelia Solandri, a common and very conspicuous epiphytic plant in most of our untouched native forests. The length of the full-grown larva (see Plate I, fig. 8) is about 1¼ in. It is subcylindrical, considerably flattened, with the head very minute, and eleven visible body-segments. Special oval warts armed with minute teeth are situated on the upper surface of body-segments 5 to 10 inclusive, similar larger warts being present on the underside, and this no doubt facilitates the insect's movements between the leaves. The colour of the larva is very dark slaty-brown, darker towards the extremities; the posterior end is considerably tapered.
Apparently only one larva inhabits each space between two sheathing leaves; and only those full of the thick brown coffee-like liquid are so inhabited.
The pupa is enclosed in a rather tough, extremely elongate silken tube situated between the sheathing leaves. It rests in an upright position in the midst of the semi-liquid mass, breathing, no doubt, being effected by means of the remarkable thoracic process. The length of the pupa is about 1½ in. It is very elongate, with the head and thorax unusually small; there is a large double breathing-process on the top of the thorax, shaped somewhat like a bivalve shell. Four of the abdominal segments are furnished on the dorsal surface with special finely-toothed warts like those of the larva, the ventral surface with plain ridges. There is a horny cremaster with two recurved hooks and several other smaller processes. (See Plate I, fig. 9.)
The perfect crane-fly appears from November till March. It is probable that the larva is feeding during the autumn and winter, and that pupation usually takes place in the spring, although the pupa which was actually reared was found in company with feeding larvae early in March.
Limnophila sinistra. (Plate I, fig. 1. ♂.)
Tipula obscuripennis Huds., Trans. N.Z. Inst., vol. 27, p. 294; not Limnophila obscuripennis Skuse, 1890. Limnophila sinistra Hutton, Trans. N.Z. Inst., vol. 32, p. 40.
This very distinct species of crane-fly is fairly common in most dense forests throughout the country.
The larva (Plate I, fig. 3) inhabits fallen tree-trunks in an advanced state of decay, forming burrows between the soft decayed portion and the harder part of the wood. It is about 1 in. in length, cylindrical, tapering towards the head, which is very small and furnished with two minute jaws and a pair of very short antennae. There are eleven visible body-segments. The extremity of the last segment is truncate and deeply excavated, the concavity being protected by five converging spines, which can be spread out or drawn inwards at the will of the insect. The orifices of the air-tubes are situated in this concavity, that of the alimentary canal being placed on the underside of the final segment, quite remote from the breathing-apparatus. Pedal warts occur on the undersides of all the segments, excepting the three immediately following the head and the terminal segment.
The pupa (Plate I, fig. 2) is about ½ in. in length, rather stout; the thoracic breathing-appendages are about one-third the length of the wing-cases; moderately stout and strongly recurved. There are two dorsal rows of hooks on each exposed abdominal segment, and one ventral row near the terminal extremity. The cremaster is bifid, strongly recurved, and very stout. The head and thorax are dark blackish-brown and highly polished; the abdomen greyish-ochreous, darker in the middle. The cremaster and extremities of the hind-leg cases are reddish. The pupa rests in a burrow made by the larva near the surface of the log.
The perfect crane-fly appears from November till March. It is practically invisible when at rest on an old fallen tree-trunk, and it is evident that the rather unusual colouring of both the wings and body has been specially adapted to harmonize with the insect's natural surroundings.
Melanostoma decessum. (Plate I, fig. 5. ♂.)
Melanostoma decessum, Hutton, Trans. N.Z. Inst., vol. 33, p. 43.
The larva of this fly (Plate I, fig. 4), which is one of the so-called “rat-tailed maggots,” feeds during the early spring in the liquid decay which occasionally involves certain portions of the inner bark of the cabbage-tree (Cordyline australis), and very possibly inhabits liquid decaying vegetable matter generally. When full grown it is about ½ in. long, of the usual maggot type, with a long breathing-tail and two short air-tubes near the head. Although apparently very fragile and gelatinous, it is really extremely tough. Its body is semi-transparent, and the internal organs are clearly visible. The head is retracted within the second segment; there are two dark patches on each side of the head which may be rudimentary eyes. A row of hooklets extends along the outer edge of the second segment, which assists the larva in progression. It is active in habit, being almost constantly on the move.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
The pupa (Plate I, fig. 6) is about 5/16 in. in length, immobile, pear-shaped, flattened beneath; the segmental divisions are very indistinctly indicated. There are several obscure tubercles on the anterior portion, and two rows, of about six in each, on the flattened ventral portion. The posterior segments are strongly curved, and bear at their extremity the breathing-tube proper. The pupa rests partially embedded in the dried portion of the decayed bark of the cabbage-tree.
The fly appears in November.