The Zoologist — May, 18G7. 726 



Ursinae, we find the males larger in Procris, Euchelia and Euthemonia ; 

 the females in Callimorpha and Euchelia; the sexes alike in Zygaena, 

 Nola, Nudaria and Arctia. In the Geometrae, the males are larger in 

 Phigalia, Nyssia, Acidulia, Scodiona, Selidosema and Hybernia ; while 

 in Urapteryx, Angerona and Amphydasis the females mostly have the 

 advantage ; but these are the exceptions : in an overwhelming majority 

 there is no disparity in size, and the same may be said of the Noctuae. 

 Certain insects are found in each group in which the sexes differ in 

 this respect from their immediate congeners: thus the females of 

 Lithosia quadra, the males of Larentia multistrigata and Miami arcuosa, 

 and the females of Nonagria Typhae and N. lutosa, are notably larger 

 than the opposite sex, and yet each of these is surrounded by closely 

 allied species in which no such difference obtains. 



In reply to these observations it has been urged that the females 

 generally are heavier, although not possessing a greater area of wing 

 surface ; but this also is hypothesis, and is not supported by the test 

 of weighing: and were it established that a gravid female exceeded a 

 male in magnitude or weight, we should scarcely render this available, 

 or pertinent to the matter under consideration. 



Disparity of Form. — In many of the instances I have mentioned of 

 the males exceeding the females in size, the discrepancy is accom- 

 panied by a marked change in form, the wings being partially or 

 entirely absent. In the genus Psyche, which, as at present constituted, 

 is perhaps the most comprehensive genus of Lepidoplera, there is not a 

 single species of which the female presents the slightest appearance of 

 a lepidopterous insect : none of them have wings, a few — a very i'ew — 

 have legs, still fewer scales, and in a great majority of those minutely 

 examined not a trace of antennae has been found. Nevertheless the 

 males are remarkable for intense and restless activity on the wing, for 

 the possession of perfect legs and for the great development of their 

 plumose antennae. In a thousand instances the volatile males of Lepi- 

 doptera escape the notice of scientific travellers, while the apterous 

 females are seen running like spiders over rocks aud on the trunks of 

 trees, and are invariably regarded as creatures Darwinized by isolation 

 or by climatal conditions. 



Disparity of Colour. — This is the most familiar, although perhaps 

 the least important, phenomenon in the variations of sex : it appeals 

 directly to our sense of sight, and cannot escape the notice of the most 

 superficial observer : as an instance I need only remind you of the 

 sooty black male, and snowy white female of Arctia mendica. But this 



