COLORATION IN POUSTES. 55 



In the carolinus group coloration is conspicuously reddish brown. 

 Yellow appears in the borders, but rarely in the metameric spots, and 

 black, if present, is confined to the ventral surface of the female and 

 limited areas in the mesothorax and metathorax and anterior part of the 

 abdominal segments. In range of pattern it corresponds very closely 

 with the darker members of the rubiginosm group, from which it is 

 separated mainly by difference in size. 



The rubiginosus group comprises the largest members of the genus, 

 and in pattern presents all transitions from the light reddish-yellow 

 texanus, with conspicuous yellow ornamentation, to the uniformly dark 

 red-brown rubiginosus. It is noticeable that here, as in the canadensis 

 group, the largest members tend to be least conspicuously colored ; 

 flavus, which perhaps stands more alone than any other species, con- 

 nects the most xanthic members of this group with those belonging to 

 the aurifer type. 



DISTRIBUTION OF TYPES. 



Plate V represents the distribution of these types in a map of the 

 United States. From this it will be seen that the aurijer type occurs 

 throughout western United States from Vancouver to L,ower California. 

 Eastward and westward it is replaced by variatus, which is the pre- 

 vailing species for the Plains and the States just east of the Mississippi 

 River. A line passing through Texas, Colorado, Utah, and Oregon 

 roughly marks the transition zone of these two species. 



The pallipes group is well represented through all the eastern portion 

 of the United States from Maine to Georgia and from the Atlantic 

 Ocean to the Mississippi River. 



The annularis group is scattered throughout southern United States, 

 the more melanic members, such as canadensis and annularis, being 

 best represented in the Gulf States ; the less melanic, such as navajoe 

 and comanchus, in Arizona and New Mexico. 



The carolinus group occurs in the Gulf and the South Atlantic States 

 as far north as North Carolina. P. rubiginosus reaches its highest devel- 

 opment, both in numbers and species, in Texas. It occurs also in 

 Florida and the other Gulf States and scatteringly as far north as Penn- 

 sylvania, southern Ohio and Indiana, Kansas, Colorado, and westward 

 to Arizona and New Mexico. In the last two States this group is rep- 

 resented almost entirely by the xanthic flavus, which is to be regarded 

 as the xanthic extreme of the series, while in Kentucky, Ohio, and 

 Illinois it is represented by the dark rubiginosus, the melanic extreme 

 of the same series. 



The most striking feature in this distribution is the increase in mel- 



