434 Transactions 



A. Order Diptera. 



In the great order Diptera, which includes all the two-winged flies, there 

 is usually very little difference in colour between the sexes, and the only 

 striking difierences noticeable, so far as our New Zealand species are 

 concerned, occur amongst the Tipulidae, or " daddy-long-legs," in which 

 the males of some of the species either have very long antennae, or 

 antennae furnished with long plumes or branches. The supposed use of 

 these elaborate antennae to the male will be explained when we consider 

 the secondary sexual characters of the Lepidoptera. The male of one of 

 our handsomest Tipulidae, Cerozodia plumosa, has magnificently branched 

 antennae. The female is at present unknown, and is possibly semiapterous. 

 ' This at least would explain why collectors have not yet succeeded in 

 finding her. 



5. Order Lepidoptera. 



Notwithstanding the fact that ornamental colouring is more in evidence 

 in the great order Lepidoptera, comprising the varied tribes of the butter- 

 flies and moths, than in any other order of insects, instances of the direct 

 operation of sexual selection are perhaps not quite so numerous or so 

 striking as might have been anticipated. It is true that in the case of many 

 species, especially amongst tropical butterflies, the males are more brilliantly 

 and beautifully coloured than the females ; yet, on the other hand, there are 

 many thousands of species where both sexes are equally ornamental. In 

 such cases Darwin assumes that the highly ornamental colours and patterns 

 were first acquired by the males* through sexual selection and afterwards 

 equally inherited by both sexes. He points out that in considering the 

 effects of sexual selection in the Lepidoptera it must be borne in mind that 

 the courtship of butterflies is a prolonged affair. The males sometimes 

 fight together in rivalry ; and many may be seen pursuing or crowding 

 round the same female. Unless, then, the females prefer one male to 

 another, pairing must be left to mere chance, and this does not appear 

 probable. If, on the other hand, the females habitually, or even occasion- 

 ally, prefer the more beautiful males, the colours of the latter will have 

 been rendered brighter by degrees, and will have been transmitted to both 

 sexes or to one sex, according to the law of inheritance which has prevailed. 

 The process of sexual selection will have been much facilitated if the con- 

 clusion can be trusted, arrived at from various kinds of evidence, that the 

 males of many Lepidoptera, at least in the imago state, greatly exceed 

 the females in number.* 



So far as New "Zealand is concerned, there is not a great number of 

 Lepidoptera where the males are more strikingly ornamental than the 

 females. The tropical-looking Hypolimnas holina, a wide-ranging species,' 

 found through the Pacific islands and Australia, and casually in New 

 Zealand, has the male blue-black, with a large white blotch in the middle 

 of each wing surrounded by a wide ring of iridescent blue. The female 

 is rather variable, black, with white and orange-brown markings ; and, 

 although highly ornamental, almost entirely lacks the brilliant glistening 

 blue which is so characteristic of the male. 



The females of our common tussock-butterfly, Argyro-phenga antipodum, 

 are usually much lighter coloured than the males, and the same applies 

 in a more marked degree to the female of our small mountain-butterfly 



* Descent of Man, 2nd ed., p. 317, 1890. 



