ART. 9 DIGGER WASPS OF GENUS PODALONIA FERNALD 7 



be almost always black. The legs, usually black, may yield to the 

 tendency to become ferruginous and then the tarsal segments, tibia 

 and femora assume this color, the last tarsal segment often less so than 

 the others. Approaching the body, the tendency to become ferrugi- 

 nous appears to struggle for ascendency with the tendency to preserve 

 the black, passing out from the thorax. The result is that the coxae 

 and trochanters (except the hind pair) are usually entirely black, and 

 the femora are streaked with black on their proximal halves. The 

 claws in all species are ferruginous of some shade, even in the totally 



black species. 



In the female of argentifrons, the abdomen is a deep blackish blue, 



and glistening. 



The usual color of the hairs is black but they seem to respond to 

 the same influences though more slowly. The more ferruginous species 

 may have pale hairs though this is not a fixed rule. Even a tendency 

 to golden yellow on the clypeal hairs is sometimes noticeable. Pubes- 

 cence is present only in the males (and on the clypeus of nicholi 

 female) as far as observed, on the clypeus and frons, and is white or 

 "silvery." The minute hairs which produce a "sericeous" surface 

 are usually brownish on the antennal filament but may be white or 

 silvery, or of other colors elsewhere. 



There appears to be a close correlation between the area occupied 

 by the ferruginous and the habitat of the insect. Thus, specimens of 

 Podalonia violacevpennis taken near the ocean or large bodies of water 

 have less red and their wings are more fuliginous than those captured 

 inland. In semiarid regions, the area occupied by the red increases; 

 the wings become more nearly hyaline and the veins lighter. In arid 

 regions, much of the abdomen becomes red, the legs tend to piceous 

 in some cases, and the wings may be hyaline. Apparently the influ- 

 ence of humidity on this species closely corresponds to that already 

 described for Sphex procerus (Dahlbom).^ 



SEX DISTINCTIONS 



There are several ways by which the sex in this genus may be 

 determined. When the sting is protruded there is, of course, no diffi- 

 culty, but if not, the novice may need to look for other characters. 



In the males there are 13 antennal segments; there are no long 

 spines on the outer side of the fore metatarsus; the margin of the 

 clypeus extends much farther below a line joining the bottom of the 

 eyes than in the female; the petiole is longer and the tip of the abdo- 

 men is rather flattened laterally. 



In the female the antenna has 12 segments; there are long external 

 lateral and terminal spines on the fore metatarsus ; the margin of the 



> Ann. Ent. Soc. Ainer., vol. 19, p. 88, 1926. 



