Carpkntior & Hewitt — Genitalia and Larva of the Warhle-flij. 275 



2. The Genital Armature. 



As in the ease of the ovipositor, we have been able to make a fairly complete 

 comparative study of the exoskeletal parts connected with reproduction in 

 the male in the two species. So far as we know, these structures have never 

 before been examined in Hypoderma, in which genus their condition throws 

 some light on the vexed question of the segmentation of the abdomen in the 

 higher Diptera. 



In the male the hinder abdominal segments are usually hidden, like those 

 of the female, by retraction within the fifth. The fifth tergum and sternum 

 (Plate XXI, fig. 3, v) are broad, especially the former, with an angular notch 

 at the hinder end of each, so that a large sub-quadrangular space is left 

 within which the tail-segments can be withdrawn. Their protrusion is 

 rendered possible by a vast extent of infolded euticular membrane connecting 

 the hinder edges of the fifth tergum and sternum with the front edges 

 of the sixth (fig. 3, vi). The sixth tergum is a distinct and fairly well- 

 developed sclerite, larger in H. Kneatum (Plate XXV, fig. 26, T. 6) than in 

 R. bovis (Plate XXIV, fig. 22, T. 6) ; the sixth sternum is much reduced. 

 In H. lineatum it is of great interest to find behind the sixth tergum 

 small but perfectly distinct vestiges of the seventh and eighth terga (figs. 26, 

 28, T. 7,8 ; fig. 29, vii, viii). Thepe are absent in H. bovis, as one of them 

 apparently is in Calliphora and Musca, so that Lowne ('95, pi. L.) and 

 Gordon Hewitt ('07, pi. 23, fig. 10) reckon the hindmost tergum in the male's 

 abdomen to be tlie eighth. The existence of reduced seventh and eighth 

 terga in S. lineatum shows that there are certainly ten segments in the abdomen 

 of male Muscoidea, the tergum hitherto regarded as the eightli being the 

 ninth (figs. 22, 26, T. 9), and the terminal dorsal plate of the abdomen 

 (figs. 22, 26, T. 10 ; fig. 26 A.) the tenth tergum. These correlations 

 render needless Briiel's suggestion ('97, pp. 530-], pi. 42, fig. 8, ix) that 

 minute longitudinal chitiuous ridges in front of the anal valves of Calliphora 

 represent the ninth tergum ; what he has identified as the eighth tergum is 

 in reality the ninth. 



It will be convenient to describe these hinder terga before pro- 

 ceeding to discuss the sternal region and the processes of the genital 

 armature. In front of the ninth tergum in H. bovis and also in B. lineatum 

 is an extensive intersegmental cuticle, beset with numerous strong hairs. 

 The ninth tergum is, in both species, a fairly large plate, emarginate 

 at its hinder edge, the emargination being shallow and sinuate in H. bovis 

 (fig. 25, ix), deeper and more angular in IT. lineatum (fig. 29, ix). This 

 tergum is prolonged backwards and latero-ventrally into a pair of prominent 



SCIENT. PEOC. E.D.S., VOL. XIV., NO. XIX. 2 X 



