COLLECTION AND PRESERVATION OF DIPTERA 411 



broader than long, projecting leaf-like in front of the head and not 

 forming a sheath for the proboscis. Abdomen with a distinct basal 

 segment and characteristic bristles ; the remaining segments indistinct. 

 Coxae of hind legs enlarged; all fifth tarsal segments elongated and 

 enlarged. Claws not distinctly toothed ; pulvilli present. Wings either 

 wanting or rudimentary. 



All the species belonging to this family, with one exception, are 

 parasitic on bats ; their life histories are unknown. 



WILLISTON'S KEY TO THE NORTH AMERICAN GENERA 



1. Wings functional, with six longitudinal and nearly parallel 



veins and three outer cross-veins ........ 2 



Wings vestigial or wanting, not functional ....... 3 



2. Thorax distinctly longer than broad; abdomen distinctly 



segmented, with two large proximal and three small distal 

 segments ; last tarsal joint not remarkably thickened . St rebla. 

 Thorax rounded, but little or not at all longer than broad ; 

 abdomen usually indistinctly segmented ; last tarsal joint 

 thickened and elongate .' Trichobius. 



3. Legs of usual length Aspidoptera. 



Hind legs greatly elongated, twice the length of the body . Megistopoda. 



THE COLLECTION AND PRESERVATION OF THE 

 BLOOD-SUCKING DIPTERA 



The only way to collect the blood-sucking diptera in large numbers is 

 to take advantage of their feeding habits ; searching for them in their 

 resting places takes up a lot of time. A tame animal, that is, one which 

 will allow the collector to manipulate a glass tube on its skin, and will 

 stand the whisking of a fly-net near it, is practically invaluable. One of 

 the authors has for many years used for this purpose a white cow, now 

 so well trained that one can sit down beside her and watch a fly feeding 

 through a pocket lens. In course of time all the blood-sucking Diptera 

 in the neighbourhood have been taken from this host. The use of such 

 a trained animal is of course not practicable when one is moving from 

 place to place, but for those settled in a laboratory it is such a great 

 advantage, and such a saving of time, that it is well worth the initial 

 trouble and cost. Animals ordinarily regarded as ' very tame ' by their 

 owners are as a rule no use for the purpose, as they resent the too close 

 attention of the collector. Failing a horse or cow which will stay quiet 

 while grazing, the next best host to collect from is one in harness, as 



