1973] 
Scriber — Papiliomdae 
36i 
to this pattern. Note that there is a considerable decrease in the per- 
centage of generalists toward the lower tropical latitudes (Figure 5). 
Discussion 
Although the absolute number of generalists is not strikingly dif- 
ferent, it is readily apparent that the percentages are considerably 
less in the lower latitudes. This fact appears to support the premise 
that there are relatively fewer generalists in the tropics and relatively 
more in the higher latitudes. There is, however, no sharp division, 
but instead a gradient of increasing relative degree of specialization 
from the extremes of latitude to the equatorial regions. It is not 
known whether increased competition could be the cause or the result 
of the increasing diversity gradients toward the lower latitudes, nor 
is it certain whether the observed gradients in feeding niche breadth 
are due to ecological release from competition in higher latitudes or 
just the inability to specialize in their unpredictable and unstable 
environmental conditions. 
It was assumed throughout this study that the niche breadth as 
measured here is that of the ‘realized’ niche as opposed to the ‘funda- 
mental’ (Odum, 1971). This study of feeding niche breadths in- 
volves a cross section of both ‘evolutionary’ and ‘ecological’ time 
(Slobodkin, 1962) and the differentiation at both intra- and inter- 
population levels. That is, there are probably areas of active compe- 
tition where we are not viewing only the neat results of evolutionary 
processes that have already and permanently narrowed the realized 
hostplant ranges from those plant families which are physiologically 
exploitable, but there are also the currently unfolding consequences 
of ecological interactions that someday may or may not result in more 
specialized herbivores. It should be noted that the relative merits of 
either specializing or generalizing may involve ‘qualitative’ and 
‘quantitative’ chemical defense of the host plants (Feeny, 1974) as 
well as other ecological factors besides competition alone. 
Emmel and Emmel (1969) have shown that for Papilio indra 
(Reakirt) and Papilio rudkini (Comstock) direct competition of 
sympatric populations is avoided most of the time by temporal isola- 
tion and utilization of mutually exclusive food-plant families. In 
one instance however they found that food did become the limiting 
resource and the separate host preferences broke down when the 
favored food became scarce. In this situation both Umbelliferae and 
Rutaceae were then utilized by the insects of these populations. 
Further evidence that competitive interactions leading to adaptations 
