158 C. G. LAMB. 



beneath. The last segment is large, and is hollowed out in a shallow pocket whose 

 boundary is shown by a dotted line. Towards the tip of the abdomen this pit is 

 bounded by a very hairy elongate papilla (P), which is very like the similar hairy 

 prominences so usual in females of this family. It is well marked and definite, and 

 can be just seen projecting beyond the end of the body when the insect is viewed 

 from above. Inside the shallow pocket lie two very stout sharply bent chitinous 

 rods, each being L-shaped, attached by the longer arm of the L to the bottom of the 

 pocket (A) with the pointed end (B) of the rod pressing against the ventral surface. 

 Between the rods the floor of the pocket is somewhat arched. Forward of these 

 rods arises a fine sharp chitinous rod. slightly curved, based as at C, with the sharp 

 point projecting backwards. The presence of these appendages causes much 

 difficulty. But for them, the general appearance of the insect, the points in which 

 it differs from the other two, the external form of the abdomen, &c, are such that 

 one would have had little hesitation in considering it to be the female of the other 

 two specimens. Remarkable chitinous appendages occur in some male Drosophilids ; 

 for example, D. obscura possesses an extraordinary five-branched chitinous appendage 

 projecting forwards from the last segment, and other species seem to possess such 

 structures, though not so highly specialized in form. ^ This process is apparently the 

 penis. Most males show no signs of such external appendages, but it is possible that in 

 such cases they are small and internal, though all that can be seen consists of various 

 complex fleshy processes. The question is one well worthy of investigation, and 

 the author is hopeful that Dr. Keilin (of the Quick Laboratory, Cambridge) may 

 be able to devote a little of his unexampled skill to the elucidation of this point in 

 some of our more common species. These chitinous processes are, as far as one knows, 

 all median and single. The female genitalia are apparently nearly always simple 

 in structure and of soft tissue, but exceptions occur in some cases. Thus, in 

 Scaptomyza graminum the abdomen is provided with two chitinous processes which 

 look like tiny saws, and in a mount they are seen to be truly saw-like external 

 appendages with sharp bordering teeth. Hence the presence in the female of paired 

 chitinous appendages is proved in certain species of the family, and thus the objection 

 to the present insect being a female (owing to their presence) is of less weight. 

 In fact, it is possible that they are homologous with the saws of Scaptomyza, and 

 have been modified in some way to suit the parasitic habits of the present species. 

 The median process is so inserted and so orientated that it is highly improbable 

 that it is a male organ. It might, indeed, be argued that we have before us the 

 males of two different species, but a close and critical comparison was made of the 

 Trinidad specimens, and the agreement in chaetotaxy, venation, and nearly all 

 the external characters is so very close, that nothing warranting such a conclusion 

 is apparent. Hence, for the present, the only thing to do is to consider the two 

 similar individuals of the Trinidad species to be males, and the third to be a highly 

 aberrant type of female of the same species. 



It may be as well to add a few words concerning the Panama species, as little 

 can be said later on. The pinned example was rather shrivelled, and so bent as to 

 make critical examination almost impossible, hence it can only be described in a 

 rather superficial manner. As far as outside appearance went, both the pinned 

 and the spirit specimens were females. Hence the latter fragments were given to 



