128 



BRITISH LEPIDOPTERA. 



(both sexes) boom along heavily only in the hottest sunshine, and are 

 entirely inactive by night ; on the other hand, the Sphingids fly 

 swiftly by night, many of the species migrating vast distances, whilst 

 by day they rest on posts, tree-trunks, and similar objects, to which 

 the colour of their roof-shaped wings assimilates. 



The shapes of the wings of the various superfamilies follow, to 

 some extent, the habits of the insects. Thus, the Sphingids have long 

 pointed wings that carry them swiftly forward in their long nights ; 

 the females of the Eucleids, Lasiocampids, Bombycids, Saturniids, etc., 

 have large wings that enable them to carry their huge egg-laden bodies 

 when ovipositing. No one has yet told us the special value of the peculiar 

 shape of the wings of the plume moths, but the resemblance of some 

 to tiny pieces of dried grass and stick is remarkable, when they have 

 their wings folded up and are at rest, but these will be dealt with at 

 length when we consider the superfamilies individually. 



The variability of the habits of the imagines of the different super- 

 families of this group is, perhaps, less remarkable than the difference 

 between the habits of the sexes of the same species. Thus in the 

 Eucleids, Lasiocampids, Bombycids, Endromids and Saturniids, as we 

 have said, the male flies swiftly in the hottest sunshine, whilst the female 

 is comparatively sluggish and rarely seen. In the late afternoon or 

 evening the males of almost all these species "assemble" freely to 

 the females (a habit also indulged in during the daytime by the An- 

 throcerids), the female flying much later for the purpose of oviposition. 

 The huge abdomina of the females of these moths explain the differ- 

 ence, for, in spite of the increase of wing area in this sex, in these 

 superfamilies, the weight of the body prevents the species flying very 

 fast, or to any very great distance. Packard associates this sluggish- 

 ness with the habit of the females laying their eggs near their cocoons. 

 He says : " When the ancestors of the moths belonging to the Bombycid 

 stirps, became arboreal feeders, the species tended to become segre- 

 gated. For example, the females of the Attaci and their allies, as 

 well as the Cochliopodids may, at first, have had larger wings and 

 smaller bodies, or been more active during flight than their descend- 

 ants. Their present, heavy, thick bodies and sluggish habits are 

 evidently secondary and adaptive, and these features were perhaps 

 induced by the habit of the females ovipositing directly upon leaving 

 their cocoons, and cocoon-spinning moths are, perhaps, more slug- 

 gish and heavy-bodied than those which enter the earth to transform, 

 as witness the Ceratocampidae, compared with the cocoon-spinning 

 Bombyx mori and the Attaci. Spinning their cocoons among the 

 -leaves at a period of the earth's history when there was no alterna- 

 tion of winter and summer, and probably only times of drought (as in 

 the dry season of the Tropics at the present time), the females may have 

 gradually formed the habit of depositing their eggs immediately after 

 exclusion, and on the leaves of the trees forming their larval abode. 

 The females thus scarcely used their wings (as in Callosamia pro- 

 methea), the males with their larger wings, lighter bodies, broadly 

 pectinated antennae, and consequently far keener sense of smell could 

 fly to a greater or less distance in search of their mates " [Bombycinc 

 Moths of America, p. 19). Among our British species the general 

 principle involved in the above may be largely true, but as a matter of 

 detail, it is open to criticism, for although the females may not 



