GUESTS AND PARASITES OF HALICTUS. 25 



very obtusely angulate at the middle and minutely toothed in front. Legs 

 slender, provided like the body with silvery erect hairs, four or more strong 

 spines on the outer edge of the hind tibiae, the tibial spurs and spines black. 



Ferruginous or somewhat darker, the mandibles, the flagellum except 

 its basal joint, /. e., the third antennal joint, more or less of the second ab- 

 dominal segment, and all of the other segments of the abdomen, from the 

 third apically, both ventrally and dorsally black. Legs including the coxae 

 piceous or black. Second segment of the abdomen with a varying extent 

 of the front margin, a diffused median vitta and the hind margin more 

 strongly black or blackish. On each side of the median stripe is a pair of 

 conspicuous rounded testaceous spots. Last ventral segment sometimes 

 reddish. 



Length, 4.75 mm. 



Woods Hole, Massachusetts. Parasitic on Halictus prui- 

 nosus (?). 



The edentate mandibles, the facetted eyes and the nodose 

 petiole of the abdomen would lead one in placing this species in 

 the small group scrupea, where it is obviously distinct from the 

 only other known female by its rugose thorax, etc. Notwith- 

 standing this, we shall have to disregard the well-marked om- 

 matidia and place the species in the group occidentalis , intermedi- 

 ate.between cariniceps Fox and mgitlosa Fox, differing from each 

 by the structure of the pygidium, etc., but related by its general 

 habitus, sculpture and chfetotaxy. 



Mutilla vesta Cresson. 



* 



Mutilla ferrugata Fabricius. 



Like the former species this too is doubtless parasitic on the 

 larger Hymenoptera such as PJiilanthus or the Pompilidae that 

 nest near by. 1 



Myrmosa unicolor Say. 



The males of this species fly about the roadside flowers while 

 the females are frequently found about the bee nests. Their 

 presence is undoubtedly due to the bees. 



Family PHILANTHID.E. 

 Philantus punctatus Say. 



This species was observed nesting in the very midst of several 

 of the colonies of Halictus. 



1 In Europe Sichel records J\I. incompleta Lep. as parasitic on Halictus (cf. Horae, 

 Soc. ent. Ross., VI., p. n) and M. coronata as a parasite of Larra anathema 

 (ibid., p. 12). 



