362 SEXUAL SELECTION. Part II. 



vermilion metallic tints; and the sexes often differ. 

 Thus, the males of some of the Agrionidse, as Prof. 

 Westwood remarks, 48 "are of a rich blue with black 

 " wings, whilst the females are fine green with colourless 

 "wings." But in Agrion Ramburii these colours are 

 exactly reversed in the two sexes. 49 In the extensive 

 N. American genus of Hetaerina, 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 ' Modern Class.' vol. ii. p. 37. 



49 Walsh, ibid. p. 381. I am indebted to this naturalist for the 

 following facts on Hetsorina, Anax, and Gomphus. 



50 ' Transact. Ent. Soc' vol. i. 1836, p. lxxxi. 



