326 W. HOVANITZ 



tudes north of 40° N., only three extend beyond 40° S. South of the 

 equatorial belt the butterfly fauna is quite depauperate, because of 

 the relative lack of typically cold-adapted forms of northern origin. 

 On the other hand, many typically tropical forms are seen to extend 

 farther southward than northward for reasons that can only be 

 conjectured but are probably a combination of (1) lack of competi- 

 tive forms in the far south and (2) warmer winters at the same lati- 

 tudes south of the equator than to the north. 



DISTRIBUTION OF GENERA AND SOME SMALLER GROUPS 



Following the chart (Fig. 1) that compares the distributions of the 

 families of American butterflies, block histograms (Figs. 2-19) are 

 presented to show the latitudinal and altitudinal distributions of the 

 genera and of certain lesser groups, when this is deemed desirable. 

 The histogram for each family is repeated, in finely crosshatched 

 form, at the head of the series of black histograms for the contained 

 genera. Within the family divisions coarsely hatched histograms for 

 the recognized subfamilies head the appropriate series of black 

 histograms. As a variation in the scheme, below the black histogram 

 (on Fig. 2) showing the distribution of the first-entered genus, 

 Papilio, there are given three coarsely hatched histograms, each of 

 which gives the range of one of the main "groups" into which this 

 large genus is first divided. Each of the hatched histograms is in 

 turn followed by black histograms for the contained natural species 

 groups; and the first of the three main divisions, the Aristolochia 

 Papilios, is first divided into sections A and B (also shown in black). 

 Under the papilionid genus Parnassius black histograms portray the 

 distribution of the three American species. In the Satyriidae, under 

 the genus Euptychia, black histograms show the ranges of the 27 

 species groups. Otherwise, the black histograms portray the dis- 

 tribution of genera. 



Papilionidae (Figs. 2-3) 



This family is represented by only four genera, of which one 

 {Papilio) is very large and is subdivided many times. It probably 

 should be divided into many genera or subgenera, but so far no 

 other really good natural division has gained acceptance. The 

 groups as organized by Jordan are satisfactory for our purpose. 



The genus Papilio has almost the same distributional range as the 



