THE BRITISH NATURALIST. [December 



and the seventh is deeply cleft. Many brachelytra have the seventh 

 dorsal segment in the male notched, or emarginate, as in some of the 

 genus AleocJiava, some of which also have the margin of the notch 

 furnished with minute teeth (A. lanuginosa ). Lathrohiiim terminaUun 

 has the seventh segment rounded in the male and somewhat pointed 

 in the female. Several species of Homalota (scapularis, suhterranea, 

 nntnmiialis, nigra,) have the last dorsal segment of the male split into 

 four teeth ; in the species of Tachinus, the last dorsal segment of the 

 male is split into four lobes, and that of the female into three, in 

 flavipes, humeralis, and nifipes, and into four, which differ, however, 

 from those of the male in shape, etc., in the other species of the 

 genus. Among the diversities of the underside of the abdomen we 

 may notice the follov/ing, treating the groups systematically for 

 convenience. Among the Geodephaga we find little of interest m the 

 abdominal sculpture, but in the genus Pterosticliiis the males of several 

 closely allied species can easily be differentiated by the condition of 

 the last ventral segment, which is always smooth in the female. 

 Thus while P. inadidus has a transverse ridge and a depression behind 

 it, P. cethiops (Avhich has been considered only a mountain form of 

 madidits) has a large tooth and a shallower depression. P. niger has 

 a keel on the last abdominal segment beneath, while P. vulgaris is 

 smooth in both sexes. P. anthracinus has a deep depression, P. nigrita a 

 tubercle, while the male of P. gracilis is simple, like the females of 

 all these species. Among the water beetles it is only necessary to 

 note the presence in the males of Agahus affinis and itnguicularis of a 

 series of striae on each side of the stridulatory file. Limnehius 

 tnincatellns has a blunt tubercle on the last ventral segment of the 

 male, while L. papposus has, in the same sex, a tuft of hair at the 

 extremity of the abdomen. A great many species of Brachelytra 

 (many species of AleocJiava, all the species of Microglossa, most of those 

 of Oxypoda, Chilopora, Calodeva, Hobates, many species of Homalota, 

 Tachyusa. etc.) — have the last ventral segment of the male narrowed 

 into a blunt point and projecting beyond the last dorsal ; but in some 

 species of Homalota {imhecilla, vestita, tibialis, etc.)- the last ventral 

 segment is rounded in the male and emarginate in the female. In 

 the males of some species the prolonged ventral plate is strongly 

 ciliate at the apex. In Conosoma, Cilea, Tachyporiis, and Tachiniis, the 

 last ventral segment of the male is so deeply notched as to expose 

 the (usually covered) eighth ; in the females of Conosoma and 

 Tachyj)onLS the last ventral segment is entire and ciliate, while in this 

 sex in Cilca it is six-lobed. In the genus Hypocyptus the sixth ventral 

 segment of the male tends to project over the deeply notched seventh ; 

 while in the males of Pliilonthus interrriedius, laniinatus, and scutatus, 

 tlie fifth ventral segment projects over and nearly covers the sixth. 



