128 



HVMENOPTERA 



CHAP. 



Fig. 50.- 



-Mimesa hicolor i . 

 Britaiu. 



information exists as to their habits; but A^erhoetf states that 



the species of Psen — like mem- 

 bers of the Pemphredoninae — 

 do not form cocoons. 



The Pemphredoninc subdivi- 

 sion includes numerous small and 

 obscure Insects found chiefly in 

 Europe and North America (Fig. 

 51, P. lugiibris); they resemble 

 the smaller black species of Cra- 

 bronides, and are distinguished 

 from them chiefly by the exist- 

 ence of at least two complete, 

 submarginal cells on the an- 

 terior wing instead of one. 

 The species of Passaloecus live in the burrows that they form 



in the stems of plants ; Pemphredon lugubris frequents the decayed 



wood of the beech. The larva and pupa of the latter have been 



described by Verhoeff; no 



cocoon is formed for the 



metamorphosis. Both these 



genera provision their nests 



with Aphidae. This is 



also the case with Stigmus 



fendidus, but the burrows 



of this species form a com- 

 plex system of diverticula 



proceeding from an irregu- 

 lar main channel formed in 



the pithy stems of bushes. 



Cemonus unicolor, according 



bramble -stems, but it also 



-Pemphredon luyubris 



Britain. 



to Giraud, forms its burrows in 

 takes advantage, for the purposes 

 of nidification, of the abandoned galls of Cynvp^, and also of 

 a peculiar swelling formed by a fly — Lijmra lucens — on the 

 common reed, Ariindo phragmiies. This species also makes 

 use of Aphidae, and Verhoeff states that it has only an imperfect 

 instinct as to the amount of food it stores. 



Sub-Fam. 10. Crabronides. — Pronotum short, front u-mg with 

 one complete suhniarginal and itvo dlscoidcd cells : hind body 



