Ciiap. X. 
NEUEOPTERA. 
363 
line ; whilst two other species w r ere attracted by shining 
white colours. 
It is an interesting fact, first observed by Schelveiy 
that the males, in several genera belonging to two sub- 
families, when they first emerge from the pupal state 
are coloured exactly like the females ; but that their 
bodies in a short time assume a conspicuous milky-blue 
tint, owing to the exudation of a kind of oil, soluble in 
ether and alcohol. Mr. MacLachlan believes that in the 
male of Libellula depressa this change of colour does not 
occur until nearly a fortnight after the metamorphosis, 
when the sexes are ready to pair. 
Certain species of Neurothemis present, according 
to Brauer 51 a curious case of dimorphism, some of the 
females having their wings netted in the usual manner ; 
whilst other females 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.” This 
latter character is generally developed in the males 
alone, but being, like every other masculine character, 
latent in the female, is occasionally developed in them. 
We have here an illustration of the manner in which 
the two sexes of many animals have probably come to 
resemble each other, namely by variations first appear- 
ing in the males, being preserved in them, and then 
transmitted to and developed in the females ; but in 
this particular genus a complete transference is occa- 
sionally and abruptly effected. Mr. MacLachlan in- 
forms me of another case of dimorphism occurring im 
several species of Agrion in which a certain number of 
individuals are found of an orange colour, and these are 
51 See abstract in the ‘Zoological Record ’ for 1867, p. 450. 
