Carpknter and Pollard — Lateral Spiracles in Hypoderma Larva. 81 



Conclusion. 



Our failure to find vestigial lateral spiracles, corresponding with those of 

 the Hypoderma maggot, in the larva of any other muscoid tiy that we have 

 examined for them is rather disappointing in view of Pantel's statement, 

 already quoted, that they are present in tachinine larvae. We have had no 

 opportunity of s.tudying examples of the last-named group, but in the maggot 

 of the bluebottle and in other dipteran larvae — that of Tipula, for example 

 — we thought that we had detected them, only to find later that we were 

 examining cuticular bristle-bearing pits from which the bristles had been 

 broken off. We do not for a moment suggest that so careful an insect- 

 anatomist as Pantel could have been deceived in this way ; but if we under- 

 stand aright his statement that "les larves amphipneustiques possedent bien 

 les stigmates et trache'es stigmatiques complementaires prevus par Palmen," 

 he seems to imply that he has detected them on all the body -segments of the 

 tachinine larvae, whereas in Hypoderma we find them only on the abdominal 

 segments from the second tc the seventh inclusive. 



If these lateral spiracles are indeed absent from many genera of muscoid 

 flies in the larval state, their presence must be regarded as a definitely 

 primitive character, and it becomes all the more surprising to find them in a 

 maggot like that of Hypoderma, specialized in many ways for a parasitic life 

 and remarkable for the extreme reduction of the anterior region, so that the 

 front spiracles, belonging to the prothorax, lie only just behind the mouth. 

 The facts set forth in this paper suggest that, if Hypoderma be really a 

 near ally of the typical muscoids, it must have diverged from the common 

 stock before these larval lateral spiracles had been lost, so that the specialized 

 parasitic habit of the group must have begun at a period comparatively 

 remote from to-day. 



The life-history of Hypoderma is of much practical interest on account of 

 the damage caused by the maggots to the hides of cattle, and this paper may 

 be regarded as a by-product of a series of researches, largely economic in 

 their object, affording an illustration of the inadvisability of trying to draw 

 a sharp demarcation between "pure" and "applied" science. Ami it may 

 be "ratifying to those who believe that morphological lines of inquiry have 

 still much instruction to yield to the student to find that one of the 

 commonest and best-known of the insect-larvae of the farm exhibits such a 

 remarkable and unexpected series of vestigial organs, which throw light on 

 the history and relationships of a highly specialized group. 



K.T.A. PROC, VOL. XXXIV, SECT. B. [L] 



