92 



THE BRITISH NATURALIST. 



[May 



sufficient constancy to be of utility in the classification of families, 

 and only occasionally can they be relied upon in the constitution of 

 any but the small genera — small, that is, in the number of contained 

 species. But though of little real value from a systematic point of 

 view, the philosophic mind is able to find much of interest in the 

 study of such details of sexual difference from the point of view of 

 their teleological significance, for, if we admit the Darwinian 

 hypothesis of evolution, we are forced to believe that these sexual 

 peculiarities have in the present, or have had in the past history of 

 the species, some purpose to fulfil in the economy of their possessors. 

 It is interesting to observe how frequently some of these modifications 

 of structure occur in wddely separated groups of beetles often differing 

 greatly in habit ; and with a view to facilitate comparison of the 

 distribution of the various types of secondary sexual characters in the 

 British beetles the subject has been approached from an anatomical, 

 rather than from a systematic point of view, and these various 

 characters will be considered under the following heads : — 



{a) size. (b) texture. (c) colour. (d) structure. 



Size. — Among the coleoptera, as in the insect world generally, we 

 find that the female tends to preponderate in size, and especially, as 

 might be expected, is this noticeable in the increased size of the 

 abdomen, which, among the British species, reaches its maximum in 

 the bloated females of Meloe and in the apterous females of Lampyris 

 and Drilus."^' In a few British beetles, however, the males are some- 

 what larger than the average females, and this is the case in the 

 larger Staphylinidae [Ocypus, Creophilus), Dysticus, Dorcus, and, most 

 noticeably of all, in the fully developed males of Liicanus cervm. 



Texture. — I use this word to denote the condition of the upper 

 surface of the insects under consideration ; and though this is a 

 character of great importance in the systematic study of the order, it 

 is only in a few groups of beetles —sometimes only in isolated species 

 — that we find any appreciable dis-similarity between the sexes in the 

 amount or character of the pubescence or sculpture, and when there 

 is a difference m texture the female is almost always duller and less 

 shining than her frequently highly-polished mate. Not only do we 

 meet with this condition among insects characterised as a group by 

 their brilliancy, as the Chrysomelidae, where the females are (as in 

 C. niarginata) of a silkier texture than the males, but also, and chiefly, 



* In the early days of spring the Wallasey sandhills swarm with the common 

 coast weevil — Philopedon (Cncorhinus) reminatns ; and these are so frequently found in 

 copula crawling on the bare sand, and the disproportion of the sexes is so great, that 

 one of my entomological acquaintances was obliged to meet the enquiries of his 

 children by informing them that the large specimens were the " mothers carrying 

 theiSr babies." 



