366 ME. WALTER WESCH^ ON THE GENITALIA OF 



thick knobs with broad bases ; Pegomy'm bicolor, Wiecl., fine blunt spines inside (PL 30. 

 fig. 134). In the Cordylviridse it is also variable, qviite long and vermiform in Scato- 

 fliaga stercoraria (PI. 29. fig. 115 ; PI. 30. fig. 116). In Melomyza similis the receptacula 

 are four in number. In TJlidia nigripennis they are three in number and of very curious 

 form (PI. 28. fig. 95). In Seioptera vibrans (Linn.) they are four in number, but double, 

 the pairs being joined by the tvibes, each pair having only one duct (PI. 30. fig. 132). 

 Several preparations of Loncluea and Toxoneura muliehrls, two; Balioptera trlpnnctata. 

 Pall., and B. combinata (Linn.), two; Sepsis cynipsea, two. 



Ephydridce. — All the Ephydridae I have examined have a single receptaculum, but 

 this is of a peculiar design. In the small Hydrellia griseola, Fall., it is very large and 

 shaped like a thimble ; in Parydra coarctata somewhat of the same shape, but longer, 

 and from the flat end proceeds a thick stalk (PI. 29. fig. 114). 



Borborid(B. — Borhorns has two, and Limnosina three receptacula. 



Remarks on those Families ivhose Genitalia have not been analyzed. 



I shall now make a few remarks on the families that have been omitted in the fore- 

 going review. 



PuUcidce. — The Pulicida3 are a doubtful group, as some morphologists place tliem in 

 a separate order (the Aphaniptera or the Siphonajitera). Mr. Verrall, however, 

 includes them in his list of British Diptera. In JPulex irritans the penis is double and 

 consists of tw^o chitinous stiles, to each of which a hyaline membrane adheres. These 

 stiles coil on themselves, at the interior extremities appearing to connect with a large 

 gland (the testes ?). In an interior position is a strong apodeme ; between it and the two 

 stiles is a membranous tube, longitudinally wrinkled, which in the Muscidoe I should 

 recognize as the sacculus ejaculatorius but for the fact that no apodeme appears to be 

 present. The upper j)art, with which the great apodeme connects, is furnished with two 

 hairy processes (the forcipes superiores) and some complicated cldtinous ones which my 

 preparation docs not clearly define. Behind the forcipes superiores is the pygidium, the 

 curious sense-organ found in both sexes of the Pulicidse. 



In the female the valves are represented by several hairy processes below the pygidium, 

 and one large receptaculum seminis of peculiar shape is clearly seen (PI. 29. fig. 113). 

 In Ceratopsyllus jubatus. Wag., the flea parasitic on the bat, one of my preparations 

 shows organs at the end of the abdomen which may represent the appendages of the 

 theca, but these insects are so minute that I cannot definitely say so. Tlie other parts 

 resemble those in P. irritans. The double stile, so far as my knowledge goes, is not in 

 favour of the idea that the Pulicidse are degraded Diptera. 



Cecidumyiidce. — In the Cecidomyiidoe one preparation shows an armature approximating 

 to that of the Chironomida?. In another the forcipes superiores and inferiores, as well 

 as the forcipes interiores, are evident and the penis is membranous ; but it is difficult or 

 impossible to determine specimens till the group has been more systematized ; a study of 

 the genitalia of prepared insects will probably be the easiest means, as otherwise they 

 keep so badly that, after a few years, only specimens mounted in balsam are of much 

 use for comparison. 



