36o 
Psyche 
[December 
Fig. 2. Latitudinal gradients in species richness for Eurasian and Afri- 
can Papilionidae. 
( x 973)- The smaller number of species of Papilionidae occurring 
in the 20-30 degree North latitude belt of figure 2 is presumably due 
to the Sahara and Arabian deserts. The great number of species in 
the 20-40 degree North latitude belts in figure 3 is correlated to a 
large degree with the strong radiation especially of the Parnassiinae 
and also of the Papilioninae subfamilies in the mountainous Hima- 
laya region and the Tibetan Plateau. (See Table 1.) There is a 
relatively sudden drop in species richness south of 10 degrees South 
latitude in figure 3, the biogeographical relevance of which is un- 
certain. 
Figure 4 shows the overall pattern of latitudinal gradients in the 
number of species of Papilionidae, corrected for distributional over- 
lap of certain species that occurred in more than one of the earlier 
three figures. Also the number of species for each tribe of Papilioni- 
dae feeding on two or more plant families and the overall percentage 
of generalized feeders for each latitudinal belt are shown in relation 
