76 Proceedings of the Royal Irish Academy. 



of several students — as the prothorax, and the doubtful series in front of this 

 be referred to the head or neck. Such is the scheme of nomenclature which 

 we adopt. In the maggot of Hypoderma (see figs. 1, 2, 3), the head region is 

 most abnormally shortened, so that the anterior spiracles lie only a short 

 distance dorsal to the mouth (see figs. 12, 13), close to the suture (figs. 12, 

 13, p.g.), that marks the boundary of the puparium-lid. The extreme anterior 

 position of this front spiracular segment in the "Warble-maggot makes it 

 unlikely that the segment can represent anything further back than the 

 prothorax. Accepting this view, the vestigial lateral spiracles occur on the 

 second to the seventh abdominal segments inclusive, and the large posterior 

 spiracles on the eighth, as suggested above. It must not be forgotten, how- 

 ever, that in the peripneustic larvae of some Diptera which may reasonably 

 be regarded as primitive— the Cecidomyidae and the Bibionidae (Morris, '17), 

 for example — the ninth abdominal segment bears a pair of spiracles larger 

 than those on the other segments. The possibility must therefore be recognized, 

 that in the grabs of the Tipulidae, in the maggots of the Muscoidea, and in 

 bapneustic and amphipneustic larvae generally, the apparent segment that 

 bears the large tail-spiracles may be due to a coalescence of the eighth and 

 ninth abdominal segment*. 



:-: on the Cuticle of the Hyfoderma Larva. 



The Warble-maggot is notoriously a " tough-skinned " insect, and sections 

 through the body-wall show the e thickening of the secondary cuticle 



(see figs. 11, 14). We have obtained fairly good results with sections cut from 

 spirit-specimens and stained with " light green," by which the two layers of 

 the chitinous cuticle usually recognized are clearly demonstrated. The outer- 

 most layer or pi thin, very hard, and stains strongly in its 

 deeper stratum (figs. 1 1. 14, rf.l); its superficial region (figs. 11, 14, d.), which 

 hardly takes tie divided into Bcale-like areas on the outer 

 surface, which, in microscopical preparations, appears like " crocodile leather" 

 (tigs. 5, 6, 13, 14). These areas correspond to the flattened epidermal cells 

 which secrete the cuticle. 



Beneath the primary cuticle is the clear, transparent, well-developed 

 sec" f iclc (figs. 11, 14, cl. 2) which does not take the light green stain, 



but shows feeble results with such a plasma stain as haemato.xylin. It 

 contains a number of clear granules, apparently harder than the general 

 substance of the cuticle ; these granules are especially numerous near the 

 attachment of a muscle, or where the spiracular air-tubes pierce the body- 

 wall (fig. 11, jr.) The innermost region of the secondary cuticle appears in 



