Chap. X. Hymenoptera. 291 



Certain species of Neurothemis present, according to Brauer, fa 

 % curious case of dimorphism, some of the females having ordinary 

 wings, whilst others have them " very richly netted, as in the 

 " males of the same species." Brauer " explains the phenomenon 

 " on Darwinian principles by 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 colour, and these are invariably females. This is 

 probably a case of reversion; for in the true Libellulte, when 

 the sexes differ in colour, 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 cha- 

 racters, 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, in some of the smaller 

 Bpecies 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 female, and contending with great eagerness 

 " who shall win the prize." 54 The Atropos jndsatoi-ius is said 

 to make a noise with its jaws, which is answered by other 

 individuals. 55 



Order, Hymenoptera. — That inimitable observer, M. Fabre, 50 in 

 describing the habits of Cerceris, 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 57 says that the males of one of the saw-flies (Tenthre- 

 dinse) " 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 mind 

 that insects belonging to this Order have the power of recognising 



53 See abstract in the 'Zoological 56 See an interesting article, 

 Record' for 1867, p. 450. 'The Writings of Fabre,' in 'Nat. 



54 Kirby and Spence, ' Introduct. Hist. Review,' April 1862, p. 122. 

 to Entomology,' vol. ii. 1818, p. 35. 57 'Journal of Proc. of Entcmolog 



55 Houzeau, ' Les Facu'.tes Men- Soc.' Sept. 7th, 1863, p. 169 

 tales, 1 &c. Tom. i. p. 104. 



