SEXUAL SELECTION 391 



cephalic horn, which is common to the males of so many 

 Lamellicorn beetles, as in Phanseus (Fig. 18). 



The old belief that rudiments have been created to com- 

 plete the scheme of nature is here so far from holding good, 

 that we have a complete inversion of the ordinary state of 

 things in the family. We may reasonably suspect that 

 the males originally bore horns and transferred them to the 

 females in a rudimentary condition, as in so many other 

 Lamellicorns. Why the males subsequently lost their 

 horns, we know not; but this may have been caused 

 through the principle of compensation, owing to the de- 

 velopment of the large horns and projections on the lower 

 surface; and as these are confined to the males, the rudi- 

 ments of the upper horns on the females would not have 

 been thus obliterated. 



The cases hitherto given refer to the Lamellicorns, but 



Fio. 23.— Blediua taurua (magnifled). Left-haod figure, male; right-hand figure, female. 



the males of some few other beetles, belonging to two 

 widely distinct groups, namely, the Curculionidse and 

 Staphylinidse, are furnished with horns — in the former on 

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

 surface of the head and thorax. In the Staphylinidse the 

 horns of the males are extraordinarily variable in the same 

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

 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 intermediate gradations. In a species of Bledius 

 (Fig. 23), also belonging to the Staphylinidse, Prof. West- 

 wood states that "mnle specimens can be found in the 

 same locality in which the central horn of the thorax is very 



'' Kirby and Spence, "Introducl. Bntomolog.," vol. iii. p. 329. 



