246 MISS A. L. EMBLETOxV ON THE ANATOMY 



the spur l^eing no louger than the first tarsal joint ; the tmsi comprise five segments, 

 the last being the claic, made up of two hooked down-curving setae. The whole leg is 

 covered with short dark hairs. 



(i) Second legs (PI. 12. fig. 30). — These difi'er from the first only in colour and in the 

 length of the tibial spur. The coxce are black, the two trochanters rather paler, while 

 the femora are almost white ; the tlbioi are yellow, and dilated distally ; the spur 

 is Icng and powerful, and by its means the creature performs the characteristic hopping 

 movements; in preserved specimens the second legs project beyond the third (PI. 12. 

 figs. 19, 20, 30). 



(j) Third legs (PL 12. fig. 28). — The small rounded coxce are silvery white, i\ie femora 

 ore brown and the tibiae black, while the tm^si are almost white, the tip of the claw being 

 black. The spur is of normal size, as in the first leg. 



(k) Abdomen (PI. 12. figs. 32, 33, 34, 35, 36, 37).— The abdomen is of a deep glossy 

 black, with numerous long dark hairs, and ventrally a soft down of short hairs. There 

 are seven segments succeeding the petiole. The structure of the exoskeleton of the 

 abdomen in the perfect insect is not easily ascertained, for there are many obscure points, 

 and it was only after dissecting a great number of specimens that I was able to arrive at 

 even an approximately correct knowledge in this matter. After trying many methods, 

 I found that the most satisfactory specimens were those that had been macerating for a 

 day or two in water, until they were quite soft and greatly distended ; in such prepara- 

 tions the black abdominal plates stand clear of each other with the swollen white 

 internal tissue showing between : this was most useful, for in such a condition one could 

 clearly and unmistakably make out the relative positions of the parts before dissection. 

 Another advantage is that the pieces of the exoskeleton can be removed one by one if 

 great care be used, and the whole series put together again on a slide and mounted in 

 Canada balsam (PL 12. figs. 34, 35, 30, 37). An alternative method, which often proved 

 very helpful, was to leave the flies in 10 per cent, (or 5 per cent.) KOII for 24 hours, 

 when all the soft parts are destroyed, the chitinous parts remaining uninjvired and in a 

 condition in wdiich they can be easily separated from one another ; when properly 

 washed, dehydrated, cleaned, and mounted in Canada balsam, the structure is seen to 

 even better advantage than in the former method, for the cbitin has become, to some 

 extent, transparent. Nevertheless, the difficulty always remains that curved and 

 rounded pieces of the armature must be flattened when mounted, rendering some 

 distortion unavoidable. This difliculty is met with chiefly in the matter of obtaining a 

 correct interpretation of the structures which go to make up the petiole (figs. 34, 35, 30, 

 37). This has a dorsal and a ventral face, each composed of two small chitinous plates, 

 of which the dorsal pair is much the thicker and stronger, being always conspicuous in 

 mounted preparations, while the ventral pieces need careful search before they arc 

 discovered. In these flattened mounted specimens, the dorsal factors of the petiole 

 appear as a dark mass situated between the side wing-like parts of the abdominal plate 

 immediately behind the petiole (figs. 34-37). In life these two lateral flaps of the 

 abdominal plate curve round the abdomen to the antero-ventral face, leaving the petiole 

 standing out in front ; its dorsal elements also curve round, forming a sort of short tube. 



