74 Proceedings of the Royal Irish Academy. 



worked out in Palnien's classical memoir (77) on the tracheal system of 

 insects. 



If the metapneustic condition he indeed the outcome of the suppression 

 of the greater number of a series of paired spiracles originally present, it 

 might be expected that some of these should be recognizable in a vestigial 

 condition. Yet it appears that no account of such reduced spiracles in any 

 muscoid or similar larva has hitherto been published, although the minute 

 anatomy of such magg - those of ihe Bluebottle (Calliphora) and the 



Housefly (Musca) has been carefully and repeatedly studied. The only 

 statement of their existence known to us in entomological literature is in a 

 brief paper by Pantel (01 ). who, without giving description or figures, writes : 

 "Ord'apres nos recherches sur les tachinaires, les larves amphipneustiques 



at bien ]• - ■ •:•; trachfes stigmatiques complementaires prevus 



par r.ihiH'ii. et ainsi se trouve justifiee, dans ce quelle a de foudaineutale, la 

 theorie tuteur." After stating that in the larvae examined by him, 



the lateral -piracies " demeurent rudimentaires a tous les stades, aussi bien 

 que gmatdquea cot intes," and pointing out that the 



J tail-spiracles cannot therefore be, as Palmen 

 imagined, due bo the approximation of spiracles originally belonging to 

 three distinct segments [sixth, seventh, and eighth abdominal], Pantel tells 

 us no more about these extremely interesting structures except that "les 



is rudimentaires abdominaux soiit situes aux niveau.x d'insertion des 



With thi if the subject in this condition, it is with great satisfac- 



tion tha fcify the presence of a paired series of minute 



ral spiracles and of solidified air-tubes connecting them with branches of 

 the main longitudinal tracheal trunks in the highly specialized larvae of the 

 Ox Warble-flies Hyp derma . These vestigial structures are present in fourth- 

 the common species of Hypoderma — Hypoderma bovis 

 r) and H . lint ■■ Villers .- well aa in the Reindeer Warble-rly, 

 ndi (Linnci. The details given in this paper have been 

 for the most part by observations on // poderma bovis. These 

 maggots live during their later stages, as is well known,. just beneath the skin 

 of the backs of cattle, the large sub-circular dorso-posterior spiracular plates 

 situated immediately l>elow the breathing-hole that is bored through the hide 

 he beast which serves as host, while, the head-end being buried in the 

 sub-cutaneous tissue, the mouth absorbs the fluid-products of the iuflamma- 

 . set up in the " warble" or swelling induced by the parasite's presence. 

 The Hypoderma larva is tl typically metapneustic in accordance with 



its l • six pairs of vestigial lateral abdominal spiracles are 



