THE BIOLOGY OF NEARCTIC LEPIDOPTERA 
I. FOODPLANTS AND LIFE-HISTORIES OF 
COLORADO PAPILIONOIDEA 
By Charles L. Remington 
Osborn Zoological Laboratory, Yale University 
In recent years the impact of evolutionary studies on 
taxonomy has greatly enhanced the interest in pairs or 
groups of species the members of which are almost indis- 
tinguishable according to the usual taxonomic criteria but 
which show no tendency to interbreed in nature and which 
differ in at least one important environmental specializa- 
tion. For these Mayr (1940) has coined the convenient 
term “sibling species”. In the Lepidoptera many instances 
have been discovered in which the siblings differ most 
strikingly in having special foodplant requirements, the 
food of each being unacceptable to the other ( e.g ., Thorpe, 
1928; Berger & Fontaine, 1947-48; Rawson & Ziegler, 
1950) . Some of these situations have been known for many 
years, and the siblings were formerly characterized as 
“foodplant races” of a single species. 
The exposure of these unrecognized sympatric species in 
the Lepidoptera is very much hampered by the lack of 
precise knowledge of the species of foodplants on which 
each species can develop successfully. By such “success” 
we ultimately refer to the plant species on which the larvae 
of the insect will feed readily without fatalities from nutri- 
tional failure or from poisoning and on which they can 
develop to adulthood with normal fertility and inclination 
to mate. Several instances are now well understood in 
which: a) females occasionally oviposit on plants on which 
the larvae cannot thrive; b) larvae appear to prosper on a 
given plant, but very high losses occur through failure to 
pupate successfully; c) larvae seemingly develop normally 
on a given plant, producing adults as usual, but the adults 
of one or both sexes show no inclination to mate and are 
apparently sterile. But for most species this precise in- 
formation is lacking, and even more limiting are the cases 
in which the food plants are completely unknown. 
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