S82 THE DESCENT OF MAN 



Brauer "explains the phenomenon on Darwinian principles 

 oj the supposition that the close netting of the veins is 

 a secondary sexual character in the males, which has been 

 abruptly transferred to some of the females instead of, as 

 generally occurs, to all of them. ' ' Mr. MacLachlan informs 

 me of another instance of dimorphism in several species 

 of Agrion, in which some individuals are of an orange 

 color, and these are invariably females. This is probably 

 a case of reversion; for in the true Libellulae, when the 

 sexes differ in color, the females are orange or yellow; 

 so that, supposing Agrion to be descended from some 

 primordial form which resembled the typical Libellulse in 

 its sexual characters, it would not be surprising that 

 a tendency to vary in this manner should occur in the 

 females alone. 



Although many dragon-flies are large, powerful, and 

 fierce insects, the males have not been observed by Mr. 

 MacLachlan to fight together, excepting, as he believes, iu 

 some of the smaller species of Agrion. In another group 

 in this Order, namely, the Termites, or white ants, both 

 sexes at the time of swarming may be seen running about, 

 "the male after the female, sometimes two chasing one fe- 

 male, and contending with great eagerness who shall win the 

 prize." " The Atropos pulsatorius is said to make a noise 

 with its jaws, which is answered by other individuals." 



Order, Hymenoptera. — That inimitable observer, M. 

 Fabre," in describing the habits of Oerceris, a wasp-like 

 insect, remarks that "fights frequently ensue between the 

 males for the possession of some particular female, who 

 sits an apparently unconcerned beholder of the struggle 

 for supremacy, and, when the victory is decided, quietly 

 flies away in company with the conqueror." Westwood" 



" Kirby and Spence, "Introduct. to Entomology," vol. ii., 1828, p. 35. 



" Houzeau, "Les Facult^s Mentales," etc., torn. i. p. 104. 



'" See an interesting article, "The Writings of Pabre," in "Nat. Hist 

 Review," April, 1862, p. 122. 



" See the "Journal of the Proceedings of the Bntomological 8ocie(y" for 

 September 7, 1863, p. 169. 



