358 



ME. WALTEE WESCHE ON THE GENITALIA OF 



of beino- cuitinous, but Lowne says that tbis colour is due to tbe " pigmented epithelium 

 -ffliich forms tbe walls " *. In Scatophaga they are a reddisb brown ; in the Tipulidse, 

 according to Dufour, white. 



Homology. — Tbey bomologize with the ovaries of tbe female. 



Phylogeny. — Tbe foregoing examination of tbe male armature shows that the greatest 

 variations are in the central organ and in the ejaculatory duct ; also that the families 

 exhibit their relationship to tbe Tipvilid or the Muscid type by tbe character of this 

 duct, whether it is of the nature of a stiff flagellum or of a flexible membane. Tbe 

 Bibionidse seem anomalous ; tbe rest of the families appear to show that tbe structures 

 of tbis part are characters of the two great divisions of Ortborrapha and Cyclorrapha. 



Segments op Abdomen, 



Before proceeding to describe tbe ovij)ositor, I propose making some remarks on tbe 

 number of segments in the abdomen of both the sexes. This number is known to 

 be variable, as tbe following table, taken at random from tbe mounted Diptera in 

 my collection, will show ; but I think the normal is probably eight. In consequence of 

 this variability, when making comparisons between the sexes it will be advisable to 

 count from tbe last segment, that bearing the valves. 



The Ovipositor. 



The ovipositor in Diptera varies in length and structure. In what are usually 

 considei'ed (on the evidence of fossil remains) the older families, it consists of valves or 

 eo-g. guides, and is not telescopic or capable of extension (PI. 24. fig. 21). It approxi- 

 mates to this form in Bibio, Culex, Chironomus, Tabanus, and Tlpula, and also in some 



' Blow-fly,' p. 660. 



