1973] 
Scriber — Papilionidae 
365 
Further speciation has apparently taken place in those regions where 
Umbelliferae are most diverse. Several of these species, however, 
are still able to utilize rutaceous food plants. 
Feeding patterns of the Papilionidae and phytophagous insects in 
general, range from strict monophagy (stenophagy) , in which a single 
species of foodplant is utilized, to wide polyphagy (euryphagy) in 
which many species, genera, or families may be utilized (Brues, 1920; 
Dethier, 1954). The exploitation of a particular hostplant involves 
many adjustments on the part of the insect to the plant’s micro- 
community. This includes host-specific predators (Brower, 1958b) 
and parasites (Read et al., 1970). Facultative polyphagy in some 
Papilio larvae, conveying the ability to take advantage of oviposi- 
tional mistakes of the adult, may allow some escape from the intense 
mortality rates that can result from host-specific parasitism (Stride 
and Straatman, 1962). Polymorphisms in larval color patterns can 
also be involved (Clarke et al., 1963), but perhaps the most im- 
portant factor in this coevolving community is the metabolic adjust- 
ments on the part of the insect to the secondary chemistry of the 
plant (Fraenkel, 1959; Jermy, 1966; and Thorsteinson, i960). As 
pointed out by Ehrlich and Raven (1965), the plasticity of the 
chemoreceptive response and the potential for physiological adjust- 
ments to secondary plant chemicals may be very important factors in 
determining the potential for evolutionary radiation in a phytopha- 
gous species. Since the possibility exists that taxonomically general- 
ized feeders may in fact be allelochemical specialists that cue in on 
one key set of chemicals in the plants, feeding niche breadth may well 
take on new meaning. 
Increased specialization by a species is generally presumed to in- 
crease the competitive ability of a species largely because the species 
utilizes its resources more efficiently (Emlin, 1966; MacArthur and 
Levins, 1964; MacArthur and Pianka, 1966; Morse, 1971; Rosen- 
zweig, 1966; and Schoener, 1971). Presumably, the less efficient 
species should be completely eliminated (MacArthur, 1972) or 
crowded to the periphery to become a specialist on another niche 
dimension (McNaughton and Wolf, 1970). In this sense, the rela- 
tive efficiencies of exploiting a critical limiting resource may in large 
part determine the niche breadth. 
Previous attempts to measure niche breadths have had varying de- 
grees of success. Various works in the literature attempt to relate 
morphological characters, behavioral repertoires or habitat selection 
response with niche breadth or overlap (Klopfer, 1962, 19675 
Schoener, 1969; Van Valen, 1965; and Wellington, 1968). Upon 
