The Males of Hemarine and other Sjihinges. 6S1 



of size and complexity affecting one side without very 

 great change in the other ; and in addition to this the 

 diminishing side appears to retain or increase its range of 

 movement, the larger side, by comparison at any rate, 

 losing it. The arrangements would seem to imply that in 

 pairing, approach is made laterally and not vertically, and 

 that to admit of this occurring more readily one side 

 becomes smaller and more movable. 



A similar change, apparently for a similar reason, is, I 

 believe, not infrequent in Coleoptera, perhaps it is only 

 ignorance that leads us to believe it rare in Lepidoptera. 

 Since it is, I think I may say, the rule, in Lepidoptera for 

 the insects to approach each other laterally, although the 

 mobility of the abdominal segments prevents this affecting 

 the actual pairing organs. It is, also, probable that the 

 approach is as often made from one side as from the other, 

 but on this point I have neither made nor heard of 

 any observations, beyond knowing that I have often, but 

 in what species I do not remember, seen the male endeavour- 

 ing to reach the female, first from one side, then from the 

 other, perhaps several times, before succeeding in his 

 endeavours. 



Still less can I guess as to the conditions obtaining in this 

 aspect, in the nearly allied family of the Trichoptera, in 

 which Mr. McLachlan records some striking instances of 

 asymmetry in the whole genus Glossosoma (European 

 Trichoptera, p. 468), as well as in Lctodcs interrupta (p. 340) 

 and Leptocerits inaeqimlis (First additional supplement, p. 

 34), in all cases with figures. 



To give any general description of the asymmetry of 

 the mdceagus as it occurs throughout the whole family 

 of Sphingides is practically impossible, so many different 

 forms does it assume. 



It is reduced to vanishing point in A. convolvidi,M. atropos, 

 Sp. ligustri, and Amhidyx rostralis, where the tube is cylindri- 

 cal and the opening terminal. In Mimas tilia) and A. popidi 

 it appears to be actually or very nearly symmetrical, but 

 there is a great difference in the armature of great spines 

 on tlie eversible membrane (true p)enis), between the two 

 sides. In Sm. ocellatus there is a great bluntly-pointed 

 projection on the left margin of the terminal opening. It 

 IS rather rare to have this eversible membrane in evidence, so 

 that its peculiarities remain easily unobserved, but except in 

 some Amorphids I have not observed it armed in any way, 



