278 Scientific Proceedings. Royal Dublin Society. 



On either side of the theca, articulating with the membranous cuticle at 

 its base, is a conspicuous hooked process, bearing fine spines, which is broader 

 in E. lineatum (figs. 26, 28, G.9 ; 27, G.9 i) than in E. bovk (figs. 22, 24, G. 9 ; 

 23, G.9 i). This pair of processes we identify, agreeing with Lowne, as 

 posterior gonapophyses ; they are termed paramera by Briiel. Between them 

 and the anterior gonapophyses are situated another pair of processes (figs. 23, 

 27, G.9e; 24, 28, G.9, angled index-line) with the tips somewhat complexly 

 hooked, especially in E. lineatum, directed outwardly, and lying partially 

 hidden by the hinder edge of the pre-genital sternum. A forwardly directed 

 extension of tlie base of each of these processes is fused with the base of the 

 anterior gonapophysis of the same side (figs. 23, 27). Nevertheless, from 

 their position we consider that they belong to the ninth, not to the eighth 

 segment, and that they may reasonably be regarded as outer posterior gona- 

 pophyses. If tliis homology be correct, the typical tliree pairs of gonapophyses 

 are to be recognized in the male genital armature of Hypoderma. This 

 would lead us to consider the organs in these insects as somewhat primitive in 

 type — a conclusion supported also by their perfect symmetry. 



In recent systematic work on the Diptera, the importance of the genital 

 armature in distinguishing species has been repeatedly enforced. The com- 

 parison of these structures in Eypoderma bovis and E. lineatum shows the 

 existence of definite specific differences. The male genitalia of the Horse 

 Bot-fly, Gastrophilus (see Schnabl and Dziedzicki, '11, figs. 647-8) show no 

 close likeness to those of Hypoderma. 



3. Pairing. 



As we have not seen the operation of pairing, we add a summary of the 

 account given by Glaser ('13, pp. 23-5), who observed the behaviour of flies 

 that he kept in cages 40 cms. long. This disposes of a fancy that the Warble- 

 flies pair only in open hill-countries. The male is ripe a day after emergence 

 from the pupa, and flies about ; the females usually remain quiet, though 

 some are rather lively, and appear to entice the male. Males were observed 

 to seize their mates sometimes on the floor and sometimes on the vertical walls 

 of the cage. There is a struggle between the paired insects, both partners at 

 times waltzing around the floor, the male beating his wings and humming 

 loudly. During these evolutions the male with his claspers or hook-processes 

 seizes the female's ovipositor, and then the pair remain fairly quiet for three 

 minutes or longer— in one case fifteen minutes. The male stands almost 

 vertically, his front legs holding the roots of the female's wings, his second 

 pair the middle region of her wings, and his hind pair resting on the ground 

 so that he can move in case the female tries to wander away. She rests usually 



