Smithsonian miscellaneous collections . he parasite evidently absorbs nutriment through its integument fromthe body liquid of the host. A special feature of the larva is thepresence of a pair of large, fingerlike diverticula containing bloodprojecting from the posterior end of the body. In the second-stagelarva (B) the body becomes distinctly segmented, and the posteriorsegments are ringed with short spines ; the mouth is open and stronglysclerotized mouth parts are present; there is a tracheal system but no 76 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 spiracles, and a few longitudinal mu
Smithsonian miscellaneous collections . he parasite evidently absorbs nutriment through its integument fromthe body liquid of the host. A special feature of the larva is thepresence of a pair of large, fingerlike diverticula containing bloodprojecting from the posterior end of the body. In the second-stagelarva (B) the body becomes distinctly segmented, and the posteriorsegments are ringed with short spines ; the mouth is open and stronglysclerotized mouth parts are present; there is a tracheal system but no 76 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 spiracles, and a few longitudinal muscles have been developed. Thecaudal diverticula of the first instar have lengthened into a pair oftails nearly half the length of the body, and fine tracheal brancheslater penetrate into their open basal parts. In the third stage the bodypreserves the general form and structure of the second stage, butthe tails have increased greatly in length, being one and a half timesor more the length of the body. In its fourth stage (C) the larva. Fig. 14.—Three larval stages of an agromyzid dipteron, Cryptochaetum iceryae(Will.), parasitic in the coccid Icerya purchasi Maskell (from Thorpe, 1931). A, first instar. B, second instar. C, fourth instar. becomes an ovoid, yellowish-white maggot composed of a head and10 body segments; the tails are greatly lengthened, slender filaments,but have become brittle and are easily broken. Each body segmenthas a belt of minute spines around its anterior end, anterior and pos-terior spiracles are now present, but the hooklike posterior spiraclesare still closed, the alimentary canal is open, the muscular system isfully developed. In Cryptochaetum striatum (Thorpe, 1941) the larval stages aresaid to be much the same as in C. iceryae, but in the third stage therespiratory tails are 10 times the length of the body and are filled forat least two-thirds of their length with fine tracheal branches. In contemplating a larva of such incomplete structure as t
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