IV INTRODUCTION. 



were utilised in copulation and gradually outdistanced those without 

 such, in other words " on the advantage which certain individuals 

 have over others of the same sex and species in reproduction," whilst 

 the words in which he sums up the means through which, probably, 

 " sexual selection " has led to the development of " secondary sexual 

 characters " are as follows : " It has been shown that the largest number 

 of vigorous offspring will be reared from the pairing of the strongest 

 and best-armed males, victorious in contests over other males, with 

 the most vigorous and best-nourished females, which are the first to 

 breed in the spring. If such females select the more attractive, and 

 at the same time vigorous males, they will rear a larger number of 

 offspring than the retarded females, which must pair with the less 

 vigorous and less attractive males. So it will be if the more vigorous 

 animals select the more attractive, and at the same time healthy and 

 vigorous females ; and this will especially hold good if the male de- 

 fends the female, and aids in providing food for the young. The 

 advantage thus gained by the more vigorous pairs in rearing a larger 

 number, has apparently sufficed to render sexual selection efficient." 



It may be well now, to run cursorily over the various " secondary 

 sexual characters " presented among our British lepidoptera with a 

 view to drawing further attention to a most interesting subject. 



(1). ANTENNA. It strikes one at once that sexual differences in 

 the antennae are not to be found in our British butterflies except in the 

 most minimised form. Slight differences in length and stoutness are 

 found in certain species of the Argynnidce, Papilionidce and Pieridce, but 

 these are so slight as to be almost unnoticeable. Amongst the 

 Sphingidce, there is a distinct difference, those of the males being more 

 decidedly ciliated than those of the females. In the Sesiidce and 

 Zygcenidoe there is again but little difference, whilst among the 

 Bombyces, made up as it is of so many unequal groups, there is very 

 considerable variation. The Hepialidce, which do not really belong to 

 this sub-division at all, have simple antennas without sexual 

 difference ; the Lithosidce and Euchelidce present slight differences, 

 the Chelonidce stronger ones, whilst in the Cochliopodidce, Liparidce, 

 Bombycidce, Endromidce and Saturniidce the differences are very great. 

 The differences are fairly well developed in the Depranulidce, Dicranu- 

 ridce, and Notodontidce. Amongst the NOCTILS:, PYRALES, CRAMBITES P 

 GEOMETER, TORTRICES, TINEINA, etc., there are considerable differences, 

 the antennae varying much in closely allied species, and showing how 

 intimate certain phases in the development of the antennae are with 

 the habits of particular species. The power that certain species have 

 of finding their mates is well-known, and it would appear that all 

 species have this power more or less developed in some form or other. 

 Generally the male, by means of some special sense, finds out the 

 female, but it is beyond doubt that the female frequently asserts an 

 external and direct attractive influence over the male. This is termed 

 " assembling " by lepidopterists. The way in which a virgin female 

 of Bombyx quercus, B. rubi, Endromis versicolor or Heterogenea limacodes 

 will, in the day-time, attract considerable numbers of males to them 

 is well known, and it is therefore necessary to examine the habits of 

 some of the species, to get some general idea of its action. We notice 

 that the species just mentioned, constitute a class of insects the males 



