364 SEXUAL SELECTION. Part II. 



invariably females. This is probably a case of reversion, 

 for in the true Libellulae, when the sexes differ in 

 colour, the females are always orange or yellow, so 

 that supposing Agrion to be descended from some pri- 

 mordial form having the characteristic sexual colours 

 of the typical Libellulre, it would not be surprising that 

 a tendency to vary in this manner should occur in the 

 females alone. 



Although many dragon-flies are such large, powerful, 

 and fierce insects, the males have not been observed 

 by Mr. MacLachlan to fight together, except, as he 

 believes, in the case of some of the smaller species of 

 Agrion. In another very distinct group in this Order, 

 namely in the Termites or white auts, both sexes at 

 the time of swarming may be seen running about, " the 

 " male after the female, sometimes two chasing one 

 t( female, and contending with great eagerness who shall 

 " win the prize." 52 



Order, Hymenoptera. — That inimitable observer, M. 

 Fabre, 53 in describing the habits of Cerceris, a wasp- 

 like insect, remarks that " fights frequently eusue 

 " between the males for the possession of some parti* 

 " cular 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 M says that the 

 males of one of the saw-flies (Tenthredinse) " have been 

 " found fighting together, with their mandibles locked." 

 As M. Fabre speaks of the males of Cerceris striving 

 to obtain a particular female, it may be well to bear in 



52 Kirby and Spence, ' Introduct. to Entomology,' vol. ii. 1818, p. 35. 



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

 Review,' April, 1802, p. 122. 



54 'Journal of Proe. of Entomolcg. Soc.' Sept. 7th, 18G3, p. 169. 



