PROCEEDINGS OF SCIENTIFIC SOCIETIES. 271 
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, illustraria, not delunaria, would 
be found to result from ilustraria.’ And again (loc. cit. p. 256) he puts it 
thus :—‘ If I. — illustraria, D. = delunaria, and — = winter; then if 
there be but one brood in the year the sequence will be J. — J. — J., and 
so on; if two broods, J. D. — f. D. — I. D., 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 pupe of 
Ephyra, but intend 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 polygoneutic species 
I believe to be true from my experience in breeding various insects. 
Remembering 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 spring 
forms are preserved through the winter in the pupal state, and so are 
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 pupe of single-brooded moths 
(e.g. Hriogaster and many Notodontida) remaining two, three, or more years 
in that stage, and then eventually making their appearance at the proper 
season with the ordinary flight of the species. 
“As bearing on the above suggestion, I may refer to what occurs in 
those single-brooded moths (Sphina Convolvuli, Acherontia Atropos, &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 perfect these delicate and highly specialized organs, and by 
a parity of reasoning it may perhaps be assumed that those pupe which 
remain longest in that stage will (ceteris paribus) produce the most highly 
developed and vitalized imagos.” 
The President read “ Notes upon a Strepsipterous Insect parasitic on 
an Exotic Species of Homoptera (Epora subtilis, Walk.) from Sarawak,” 
accompanied by drawings illustrating the metamorphosis. He also read 
Notes on the Genus Prosopistoma, especially with regard to the species 
from Madagascar described by Latreille, of which he exhibited the types. 
