Fussorial Ilymcnoptera of North America. 91 



Length of body, .33 ; head and thorax together, 18 ; abdomen, 15 

 inch. 



Illinois, (Coll. Ent. Soc. Phil.). 



Its three-toothed mandibles, non-striated enclosure of the propo- 

 deum, coarsely punctured head and thorax, shorter interspaces of the 

 wings and dull colors; also the other wing characters, the slightly sub- 

 pedunculate abdomen and long, slender legs will easily separate this 

 interesting species from C. sex-mac ulata, to which it is allied. 



Crabro auriceps. Oresson. 



C. auriceps, Oresson, Proc. iv. p. 150. (1865.) 



Into this section falls this interesting species. Its head is still more 

 cuboidal than in the preceeding species, being as long as broad and 

 si|uare in front, like the $ of C. quadriceps, while the abdomen is 

 much more pedunculate, the basal joint being nodose above. 



This is an instance of the great variability of the species of a genus 

 of wide geographical range in those characters which are structural, and 

 scarcely sj)ecific, as in the present species where the head is remark- 

 ably large, and the attachment of the abdomen to the thorax much 

 attenuated. In these tropical species much more of the body is highly 

 colored than in those inhabiting the temperate zone ; as in the present 

 instance, where the scutellum is not only yellow, but also the side pieces 

 as well as a slight spine just above the insertion of the wing. 



Cuba, (Coll. Ent. Soc. Phil). 



Crabro sex-maculatus. Say. 



Crabro se.c-maculatus, Say, Keating's Narr. Long's Exp. p. 341. (1821.) 

 Harris, Cat. Ins. Mass. p. 68. (1835.) 

 Smith, Tat. Hym. Br. Mus. iv. p. 418. (1856.) 

 Cresson, Proc. iv. p. 485. (1865.) 

 % . Short, thick and stout. Head larger than usual, in form not 

 differing essentially from the 9 , being cuboidal, about one-fourth 

 broader than long, not narrowing behind any more than in $ , nor 

 does the front differ. The head is a little more coarsely punctate, 

 black, no hirsuties in front, orbits as usual silvery, clypeal region 

 silvery, clypeus itself prominent, well carinated, black beneath the 

 pubescence. Mandibles with a large acute tooth just inside the mid- 

 dle of inner margin; usually black with a yellow streak in the middle, 

 or pale yellow, and black at base and corneous at tip. Antennae long 

 and slender, scape slender not dilated, but a little angular, yellow with 

 a black ovate spot on the inside, flagellum black, slightly toothed 

 beneath. 



Thorax more coarsely punctured than in 9 '■> prothorax yellow, in- 



