SEXUAL SELECTION. 
Part IE 
o/»o 
vermilion metallic tints ; and the sexes often differ,. 
Thus, the males of some of the Agrionidse, as Prof. 
Westwood remarks / 8 “are of a rich blue with black 
“ wings, whilst the females are fine green with colourless 
“wings.” But in Agrion Bamburii these colours are 
exactly reversed in the two sexes . 49 In the extensive 
N. American genus of Hetmrina, the males alone have 
a beautiful carmine spot at the base of each wing. In 
Anax junius the basal part of the abdomen in the male 
is a vivid ‘ultra-marine blue, and in the female grass- 
green. In the allied genus Gomphus, on the other 
hand, and in some other genera, the sexes differ but 
little in colour. Throughout the animal kingdom, 
similar cases of the sexes of closely-allied forms either 
differing greatly, or very little, or not at all, are of 
frequent occurrence. Although with many Libellulidae* 
there is so wide a difference in colour between the sexes, 
it is often difficult to say which is the most brilliant ; 
and the ordinary coloration of the two sexes is exactly 
reversed, as we have just seen, in one species of Agrion. 
It is not probable that their colours in any case have 
been gained as a protection. As Mr. MacLachlan, who 
has closely attended to this family, writes to me, dragon- 
flies— the tyrants of the insect-world — are the least 
liable of any insect to be attacked by birds or other 
enemies. He believes that their bright colours serve 
as a sexual attraction. It deserves notice, as bearing 
on this subject, that certain dragon-flies appear to be 
attracted by particular colours: Mr. Patterson observed 50 
that the species of Agrionidse, of which the males are 
blue, settled in numbers on the blue float of a fishing 
48 1 Modern Class.’ voi. ii. p. 37. 
49 Walsh, ibid. p. 381. I am indebted to this naturalist for the* 
following facts on Hetserina, Anax, and Gomphus. 
50 ‘ Transact. Ent. Soc.’ yol. i. 1836, p. lxxxi. 
