82 
PAPERS READ BEFORE THE SOCIETY. 
-==@333a©3«a=-- 
SECONDARY SEXUAL CHARACTERS IN BRITISH COLEOPTERA. 
(Read May 2nd, 1S99, by H. HEASLER). 
In bringing the subject of secondary sexual characters before the 
Society, it is more particularly with the idea of drawing the attention 
of the members to the importance of these characters in throwing 
light on the history and development of insect genera, than the recital 
of a host of these characters, which are either well known or which 
convey no information to anyone who is not actually a coleopterist. 
For this purpose I propose omitting those characters whose utility is 
obvious, such as the dilated tarsi in our Geodephaga, the suckers on 
the anterior tarsi of Dytiscus, the antennal development in the cock¬ 
chafer, &c., and shall deal more with those obscure characters which 
are so difficult to understand. This side of the question has always 
had for me a particular fascination, and it is only by the actual study 
of these structures, and their connections and points of resemblance in 
closely allied species, that one is able to trace something of the lines 
along which the numberless species of insects have been, or are being, 
developed by natural laws. The subject then becomes surrounded 
Avith an interest which the bare compilation of facts could never have 
given to it, and when facts have been compiled without some theory 
or working basis to go upon, it is generally found that they are useless 
for the purpose of any theory that may be subsequently developed, 
as the facts have not been got together in a way that the theory 
necessitates. 
It may be in the memory of some of the members that when I 
read a paper on the subject of beetle coloration, I endeavoured to show 
by studying the coloration of certain groups that it was possible to see 
in some measure the past history of the family by this means alone, 
and it is with a similar object in view, namely, that of showing how 
the secondary sexual characters of insects assist us in forming some 
knowledge of the history of the families and genera displaying them, 
that I intend to treat the subject of secondary sexual characters. 
With this object in view I want to draw your attention especially to 
the family of the Dytiscidae or carnivorous water-beetles. I have read 
somewhere, I forget now where, that the reason given by someone of 
the fact that the females of so many of our water-beetles were rough 
where the males were shiny was for the purpose of assisting the male 
during copulation by giving a better surface to which to cling. This 
explanation seemed to me to be particularly ill-adapted to the facts of 
the case, since in the genus Dytiscus, where the roughness reaches the 
maximum, the male insect has very elaborate and well developed 
suckers on the anterior tarsi, which as everyone knows are con¬ 
trivances suited only to a smooth surface, and the rule is the smoother 
