"feeding up quickly") the completion of the [lupal btaj^'e is accelerated, 

 then delunaria produces delunaria, not iUustraria. Further, it is my belief 

 that the converse will be found to hold good, viz. that should the completion 

 of the pupal stage be retarded either by cold seasons or climates in a state 

 of nature, or artificially by aid of an ice-well, iUustraria, not delunaria, would 

 be found to result from iUustraria.' And again (he. cit. p. 2.36} he puts it 

 thus: — 'If /. = iUustraria, D. = delunaria, and — ==^ winter; then if 

 there be but one brood in the year the sequence will be /. — I. — /., and 

 so on ; if two broods, I. D. — I. D. — I. I)., and so on ; if three broods, 

 I. D. D. — I. D. D.., and so on.' 



" T have not yet tried the effect of artificial retardation on the pup« of 

 Ephijra, but iutend to do so when opportunity offers. My experiment 

 shows that the effect of natural retardation over the winter months is to 

 produce the type whatever may be the form of the parents ; and that such 

 natural retardation does usually (? always) occur in double-brooded species 

 I believe to be true from my experience in breeding various insects. 

 Kemembering that the summer broods of season-dimorphic species are 

 smaller, and apparently vitally weaker than the spring ones, and that it is 

 from the former that the latter are usually descended, may we not assume 

 that the provision by which some few of the direct offspring of the sprino- 

 forms are preserved through the winter in the pupal state, and so arc 

 enabled to pair with the offspring of the summer form, is of advantage to 

 the species, in affording a ' cross ' between individuals which have developed 

 under very different conditions ? A similar benefit may be derived in the 

 commonly observed case of individual pupa3 of single-brooded moths 

 {e.g. Eriogaster and many Xotodontidce) remaining two, three, or more years 

 in that stage, and then eventually making their appearance at the proper 

 season with the ordinary liight of the species. 



"As bearing on the above suggestion, I may refer to what occurs in 

 those single-brooded moths {Sphinx Convohuli, Acherontia Atrojws, &c.}, 

 which sometimes appear abnormally from the pupa before the winter 

 hybernation, or which by 'forcing' have been artificially so developed. It 

 has been stated, I believe, in most such cases in which an anatomical 

 examination has been made, that the ovaries, &c., were found in an abortive 

 or rudimentary condition. This goes to show that a long period of quiescence 

 is necessary to perl'ect these delicate and highly specialized organs, and by 

 a [larity of reasoning it may perhaps be assumed that those pupae which 

 remain longest in that stage will [ceteris paribus) produce the most highly 

 developed and vitalized images." 



Papers read. 

 I'lie President read " Notes upon a Strepsipterous Insect parasitic on 

 an Exotic Species of liomoptera (Epora subtilis, Wulk.) from Sarawak," 



