ASXLIM. 
603 
velox, an orthopteron.) There is a large field for interesting work on 
these lines in India, and the student should consult Prof. Poulton’s 
paper. Some of the Asilids are very large, and several (especially the 
Laphrince) look much like bees, having a comparatively short and 
thick body (PL LXIV, fig. 7) ; others {Leptogaster , fig. 395) are of the 
most slender build, with a very long thin abdomen, and no pulvilli 
on the feet. These are not uncommon in the hills, and the prevalence 
of this elongated body-form, not in this family alone but in others 
also, seems to be a characteristic of the flies of that region as 
compared with those of the plains. Why this should be is at 
present an unanswerable question. In the case of the Bombyliid 
Systropus (PI. LXIII, fig. 4) the strong resemblance which it certainly 
has to long-bodied Hymenoptera common in the same locality may very 
possibly be of benefit in some way ; we do not know in what way. The 
same might perhaps be said of the elegant little Syrphids of Baccha, 
Sphegina, and allied genera (PL LXY, fig. 4), but not of Leptogaster 
since this is not like any common Hymenopteron, and in this case 
some other explanation must be sought. Perhaps the requirements of 
their larval stages are not fulfilled in the plains ; perhaps the large 
surface exposed on the long abdomen is uncomfortable in very hot dry 
conditions ; it may be that the flies prey especially upon certain species 
of insects which occur in abundance only in the hills, or they may have 
some parasite or other enemy which lives only in the plains. These are, 
of course, the merest suggestions, and entirely valueless, as all such 
speculations must be until backed up by adequate knowledge of the 
life-histories and physiology of the insects. In one respect we may say 
with some certainty that the attenuate 
shape of Baccha and Leptogaster is of 
advantage, and that is as a protection, 
at any rate from human enemies, for 
unless shown up by a light background 
they are very noticeably inconspicuous. 
Another point which is perhaps worth 
notice is the strong likeness in form and 
general build between Leptogaster and 
Dragon-flies. It is probable that this 
superficial likeness in two such distantly 
Fig. 395— Ax Asxlid (Lepto¬ 
gaster) Simla. 
