INTRODUCTION. Xlll 



and space occupied by the ova compared with the rest of the body, and 

 the greater wing area due to the positive necessity of larger structures 

 to carry the greater weight when the female shall fly for the purpose 

 of oviposition, and still further would " a sluggish conservative habit 

 of body " affect the size of the imagines at all, considering that this 

 (size) is positively determined in the larval stage, long before the per- 

 fect insect has a separate existence and therefore " conservative habits " 

 to indulge in ? I fail to see its effect in our lepidoptera, as the larvae 

 which produce females, as a rule grow somewhat larger than those 

 which produce males, but I have never noted any difference in habit 

 in the larvae which produce the different sexes, except in one instance, 

 that of Orgyia antiqua, and then in that species, the female larva 

 wanders about immense distances to pupate, but its more active habits 

 do not prevent it producing a moth with an immense body compared 

 with that of the male. As to difference in the size of the larvae which 

 are to produce males and females, Dr. Chapman has recorded that 

 antiqua female larva has one more moult than the male larva, and that 

 the male nevertheless is longer in pupa than the female. Probably this 

 occurs in other species. 



(5). SHAPE. The shape of the wing is occasionally a secondary 

 sexual character and is sometimes very marked, although it must be 

 confessed that shape is generally rather comparative than absolute and 

 to a certain extent dependent on sexual variation in size. The male 

 Lyccena astrarche is narrower- winged than the female ; in Hepialus 

 sylvinus and H. velleda, the wings of the female are larger and broader ; 

 in lupulinus and hectus, longer but narrower in comparison than those of 

 the males ; whilst in Neuroma popularis, Galleria mellonella and Aphomia 

 sociella, the wings are much broader and more ample in the female ; 

 the female of Nonagria neurica has a more pointed wing, and so usually 

 has the female of Viminia albovenosa. The same character is essentially 

 well-developed in Chilo phragmitellus,mucronellus and Cledeobia angustalis, 

 but whilst the first mentioned generally has the pointed character allied 

 to a greater wing area, the last has the wings much less ample in 

 the females than in the males. The females of Chortodes arcuosa, 

 Stilbia anomola, Hydrilla palustris, Rusina tenebrosa and Scapula alpina 

 have small square wings compared with the exceptionally full and 

 ample wings of the males. Although striking instances of difference 

 in the shape of the wings in the two sexes are comparatively rare 

 among our British species of lepidoptera, some of the tropical butter- 

 flies give examples which are extreme. Among the American 

 lepidoptera Scudder mentions that Chlorippe in the female has " the 

 hind wings full and rounded, while those of the male are angulated, 

 the outer margin being nearly straight ; " the fore wings of the male 

 of Strymon titus have "pointed tips and the hind wings have the 

 inner angle sharply defined, while in the female, both the tip of the 

 fore wings and the inner angle of the hind wings are broadly rounded." 

 I have before mentioned that sexual difference in shape is to a great 

 extent coincident with sexual difference in size. This is especially 

 noticeable among our Bombyces, among the NocTiLaE, Neuronia popu- 

 laris, Noctua umbrosa, Hydrilla palustris, Agrotis cinerea, Rusina tene- 

 brosa being examples, whilst the difference in the shape of the wings 

 of the males of Galleria mellonella and Aphomia sociella are very re- 



