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Simuliidae
Austrosimulium vexans Mik. This species is recorded by Lamb (1909) from Campbell Island and Auckland Island, but there is some confusion in his record since Auckland Island, the type locality, is given as a new locality, and Mik is quoted as the authority for the Campbell Island record. The names of the two islands may have been transposed and Lamb may have seen specimens from Campbell Island.
Specimens of adult females were collected by Mr. R. J. Langbein on the window of a hut on Campbell Island, in December, 1949. The adults of vexans Mik and ungulatum Tonnoir are the only New Zealand species with strongly toothed tarsal claws, but the two may be separated by the colouration of the base of the third antennal segment, which is red in ungulatum and black in vexans. Mr. Langbein also sent two larvae collected from leaves dipping into a small
Fig. 8.—Austrosimulium vexans Mik., antenna of larva.
Fig. 9.—Austrosimulium vexans Mik., submental plate of larva.
Fig. 10.—Austrosimulium vexans Mik., gill spot of larva.
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stream, in January, 1949. Both larvae showed gill spots. A later attempt by Mr. D. A. Challies to secure pupae was unsuccessful, but he sent more larvae, one of which had the gill spot present. The larva of vexans has not previously been described, and the pupa is still unknown, but the structure of the gill spot indicates that the pupa when found will be readily distinguishable from all other New Zealand species.
Larva. Length 4.5 mm. Dorsum of head without evident pattern. Length of first and second joints of antenna in ratio 1:1.5. Apical pseudo-joint of first joint less than one quarter the length of the whole joint. Teeth on submental plate as in Fig. 9. Gill spots (Fig. 10) with filaments coiled anteriorly. The gill filaments are relatively few, six to eight longer filaments and one or two shorter.
Fig. 11.—Austrosimulium vexans Mik., caudal view of anal segment of larva.
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They are relatively wide in basal diameter (0.025 mm.) and only slightly tapered distally. On the caudal segment the ventral papillae are present, and the rectal gills are tri-lobed with the lobes simple. The semicircular ventral ring sclerite is present, but the dorsal ends of this sclerite (Fig. 11) are not expanded, or very slightly expanded.
Of the New Zealand species of Austrosimulium this larva is most like A.tillyardi Tonn. in the small number and large diameter of the gill filaments, but all the New Zealand species (except ungulatum, which is unknown) have a much larger expansion of the dorsal ends of the ventral ring sclerite. On adult and larval characters vexans would fall in Mackerras' (1949) “mirabile group” with toothed claws in the adult and the ring sclerite and ventral papillae present. Of the Australian species of Austrosimulium,vexans is most like crassipes Tonnoir in the small number of gill filaments, the width of the gill filaments, and in the lack of prominent expansions on the dorsal ends of the ring sclerite, but the gill filaments are shorter than in crassipes.
The larvae collected by Mr. Challies were “mostly found on rocks on the side of dammed up, slow running streams, moving over the peat deposit on the rocks like small maggots.” Examination of the stomach contents of three larvae did not disclose any diatoms such as frequently pack the stomach of larvae of some of the New Zealand species.