Chap. X.] COLEOPTERA. 363 



the lower surface of the body," in the latter on the upper 

 surface of the head and thorax. In the Staphylinidae the 

 horns of the males in the same species are extraordinarily 

 variable, just as we have seen with the Lamellicorns. In 



Fig. 22.— Bledius tauras, magnified. Left-hand figure, male ; right-hand figure, 



female. 



Siagonium we have a case of dimorphism, for the males 

 can be divided into two sets, differing greatly in the size 

 of their bodies, and in the development of their horns, 

 without any intermediate gradations. In a species of 

 Bledius (fig. 22), also belonging to the Staphylinidae, male 

 specimens can be found in the same locality, as Prof. 

 "Westwood states, "in which the central horn of the tho- 

 rax is very large, but the horns of the head quite rudi- 

 mental; and others, in which the thoracic horn is much 

 shorter, while the protuberances on the head are long." " 

 Here, then, we apparently have an instance of compensa- 

 tion of gi'owth, which throws light on the curious case 

 just given of the loss of the upper horns by the males of 

 Onitis farcifer. 



Law of Battle. — Some male beetles, which seem ill 

 fitted for fighting, nevertheless engage in conflicts for the 

 possession of the females. Mr. Wallace " saw two males 

 of Leptorhynchus angustatus, a linear beetle with a much 



*• Kirby and Spence, iliid. vol. iii. p. 329. 



'^ 'Modern Classification of Insects,' vol. i. p. 1*72. On the same page 

 there is an account of Siagonium. In the British Museum I noticed one 

 male specimen of Siagonium in an intermediate condition, so that the 

 dimorphism is not strict. 



«» 'The Malay Archipelago,' vol. ii. 1869, p. 278. 



