1892.] 



THE BRITISH NATURALIST. 



187 



upright, sharp, and very strong horn or tooth, forming an outer margin 

 to the depression. In the genus Ontliopliagns, remarkable for the 

 horns on the head of the males, there is a tendency for the thorax of 

 the female to become elevated into a rounded protuberance — some- 

 times two protuberances separated by a groove in front. The 

 lozenge-shaped area situate between the intermediate legs in the 

 Aphodii, and which is generally known a? the mesosternal (sometimes, 

 but incorrectly the meta-sternal) area almost always differs sexually, 

 and frequently offers excellent points for the discrimination of cloh^ely 

 allied species. While in the females it is usually smooth and hat or 

 slightly convex, in the males it is usually more or less depressed and 

 frequently punctured and hairy. The meta-sternum is impressed in 

 the males of Scaphidiiini ; that of Agathidiiini atnim is depressed in 

 the male and furnished with a tuft of hair ; and in the same sex of 

 Strangalia nigra and avuiata the meta-stenum bears two crests of hair. 



Elytra. — As appendages of the thorax the elytra will 

 next require our attention, and. since in the great majority 

 of beetles (except in the sub -order Brachelytra) the wmg- 

 covers from the most conspicuous portion of the insect's body 

 it will be convenient under the same head to consider se ..^e 

 instances where the whole outline of the insect differs sexually 

 either from modification of the thorax and elytra, of the elytra 

 alone, or from absence of these latter organs. Among the Elateridae, 

 and most noticeable in Athons niger, A. longicollis, Sericosomus bvuuneus 

 and Campylus linearis, the male insect is much narrower than the female 

 which has the outline, especially of the elytra, somewhat rounded. 

 The males of Gonioctena and Lagria hivta are smaller and narrower t.^^an 

 the females, and the same sex of Blaps mucronata is also narrower, 

 with the produced tip of the elytra longer than in the female. Several 

 of the Carabi, especially C. violaceus, have the elytra of the female 

 much more rounded at the sides than those of the male ; the female of 

 Calosoma is distinctly dilated behind and produced at the apex ; 

 Pterostichus niger and vulgaris have the female elytra altogether 

 broader ; the females of Hydnrna usually have the elytra shorter and 

 broader and more flattened behind ; some Carabi, especially C. 

 grannlatus and nenioralis, have the elytra of the female very strongly 

 sinuate before the apex ; in several species of Silpha [tlioracica, riigosa, 

 sinuata, e.g.) the elytra of the males are truncate or obtuse, those of 

 the females are sinuate and produced at the sutural angle. The 

 females of several Aphodii (lapponiiiu , fcvfidnsj ha\e the elytra 

 distinctly dilated behind, and the same is the case in the females of 

 Tiliiis elongatiis. The sexes of at least two species oi Ptinus (licJwnuni 

 and fu-r) differ so much in shape as to appear specifically distinct, for 

 while in the male the elytra are oblong, with nearly parallel sides and 



