( xxxii ) 



far (■(iiiliiu'd tli(.'nisclvfs to anli'iit liaplism dI' iiidiviilual vai'iuties showing some 

 distinct ion only in colonr, jiiittern, or sliapc. There is, of course, no reason 

 for such restriction. There is just as much justification in Le])ido{)tera as there 

 is in beetles for naming structural varieties. If it is not objectionable to baptise 

 sculjiture-varieties of Carabus, there can also be no objection against providing 

 with a name, for instance, the numerous individuals of Chalcosiidae which are 

 different in neuration. However, it is our oj)inion that the naming of individual 

 varieties should not go further than is necessary, and that only the student of 

 variation can decide how far it is necessary. 



Conspicuous individual variability is observed among Sphingidae both in 

 the larvae and the adults, the caterpillars of Macroylossum and Cephonodcs and 

 tlie imagines of some Ambidicinae being very variable in colour. 



The differences between jiareut and offspring are no less marked in many 

 instances than those of the offspring inter sc. The generations as tiiey follow 

 one another are either practically the same, or there is a cycle of more or 

 less different generations. In Lepidoptera the cycle is generally restricted 

 to two or three broods. As these coincide in time of appearance with the 

 seasons as a rule, this particular kind of " gemratonj " variation is called 

 seasonal. Though as a matter of course the individuals of each separate brood 

 are a biological entity varying individually in the way explained above, 

 there is nowadays a great inclination amongst systematists as well as 

 biologists to confound seasonal with individual variation. If two different 

 specimens are offspring of the same female, they are snrely not seasonal 

 varieties. At the bottom of the confusion lies the assumption that, since 

 seasonal variation depends on meteorological differences of the seasons, all 

 differences are caused to appear by such factors. This assumption is certainly 

 incorrect, and therefore the indiscriminate treatment of different- looking 

 specimens as seasonal quite misleading. Everybody may draw conclusions as 

 he pleases, but the facts must be represented as they are ; they must not 

 be tampered with. Seasonal variation is observed in several instances among 

 Sphingidae. The most remarkable cases are found in Iliemorrhagia and 

 Hyloiciis. Though we know that generatory variation is often structural in 

 insects (^Aphidae, Physopoda, etc.), we were nevertheless surprised to find 

 a structural difference in the claw-segments of tiie two forms of Hi/loicus 

 perelegans, which forms we presume will turn out to be seasonal. 



Having studied the differences between the individuals proved by rearing 

 to be parents and offspring, the student will be able to select from the 

 individuals at large those which a comijarison of their bodies convinces him to 

 be so nearly identical with the specimens reared that they might very well be 

 brothers and sisters of tiiem. But knowing that corijoreal similarity is no 

 absolute proof of biological identity, he will prudently test his conclusion — 

 perhaps gather some female moths which come to his lamp and which seem to 

 him identical to all intents and i)urposes, get eggs from them, and rear the 

 larvae. To his astonishment he finds that the apparently identical females have 



