35G SEXUAL SELECTION. [Part II 



tection, except in the case of some flower-feeding species ; 

 and we cannot believe that they are purposeless. Hence 

 the suspicion arises tliat they serve as a sexual attrac- 

 tion ; but we have no evidence on this head, for the sexes 

 rarely diflfer in color. • Blind beetles, which cannot of 

 course behold each other's beauty, never exhibit, as I hear 

 from Mr, Waterhouse, Jr., bright colors, though they 

 often have polished coats : but the explanation of their 

 obscurity may be that blind insects inhabit caves and 

 other obscure stations. 



Some Longicorns, however, especially certain Prioni- 

 dce, offer an exception to the common rule that the sexes 

 of beetles do not difter in color. Most of these insects are 

 large and splendidly colored. The males in the genus 

 Pyrodes,^' as I saw in Mr. Bates's collection, are generally 

 redder but rather duller than the females, the latter being 

 colored of a moi'e or less splendid golden green. On the 

 other hand, in one species the male is golden green, the 

 female being richly tinted with red and purple. In the 

 genus Esmeralda the sexes differ so greatly in color that 

 they have been ranked as distinct species : in one species 

 both are of a beautiful shining green, but the male has a 



68 pyrodes pulcherrimus, in which the sexes differ conspicuously, has 

 been described by Mr. Bates in 'Transact. Ent. Soc' 1869, p. 50. I will 

 specify the few other cases in which I have heard of a difl'erence in color 

 between the sexes of beetles. Kirby and Spence (' Introduct. to Ento- 

 mology,' vol. iii. p. 301) mention a Cantharis, Meloe, Rhagium, and the 

 Leptura tcstacta ; the male of the latter being testaceous, with a black 

 thorax, and the female of a dull red all over. These two latter beetles 

 belong to the Order of Longicorns. Messrs. R. Trimen and Waterhouse, 

 Jr., inform me of two Laniellicorns, viz., a Peritrichia and Trichius, the 

 male of the latter being more obscurely colored than the female. In 

 Tillus elouffaius tlie male is black, and the female always, as it is believed, 

 of a dark-blue color with a red thorax. The male, also, of Orsodacna 

 atra, as I hear from Mr. Walsh, is black, the female (the so-called 

 0. ruJicoUis) having a rufous thorax. 



