276 
Psyche 
[June-September 
developmental temperatures, but low temperatures cannot induce 
diapause in long-day animals. (This system was first demonstrated 
for P. rapae (L.) by Barker, Mayer, & Cohen (1963).) When non- 
diapause, long-day pupae of P. n. venosa are chilled, they produce 
vernal phenotypes; thus diapause is not necessary to produce them. 
However, it is not known whether all diapause individuals are 
irreversibly determined phenotypically, because they have a manda- 
tory chilling requirement and break diapause in mid-winter, thus 
assuring that every individual will receive some post-diapause 
chilling. The entire system is summarized in Fig. 1. 
Although the necessary experiments to clarify this point have not 
been completed with P. n. venosa, they have been in the literature 
for 50 years in a very important paper which has been universally 
overlooked by English-speaking workers (Lorkovic, 1929). Lorkovic 
worked with P. rapae and, to a lesser extent, Pontia daplidice (L.). 
It is worth quoting at some length from a translation of the 
summary (“homodynamic” pupae are non-diapausers; “heterody- 
namic” are diapausers): 
“Not only the homodynamic but also the heterodynamic 
pupae of P. rapae are strongly influenceable in respect to 
the butterfly’s markings. If the homodynamic pupae are 
put in heat (25-30° C) during the sensitive period (which at 
25° sets in about 12 hours after pupation), they produce 
strongly black-spotted butterflies, while cold (5° C) brings 
about a disappearance of these spots as well as a densely 
dark powdering of the hindwing underside. Naturally 
there are formed at corresponding temperatures also all 
intermediates between the two extremes. The hetero- 
dynamic pupae produce as a whole intermediate forms . . . 
but, contrary to the results of Siiffert (on A. levana — 
A.M.S.), the heat form can also be produced by a high 
temperature of 32° C; but the black marking of the fore- 
wing always approaches the heat form more than the hind- 
wing underside, which can never attain the extreme grade 
of the heat form. At lower temperatures the spotless form 
is occasioned. The influencing of the heterodynamic pupae 
by temperature is successful only during the last section of 
development; pupae which for 3 months were kept at 
lower temperatures (—5° to +10°) produced heat forms 
after 6-8 days of exposure to higher temperature (32°). 
