FIELD BOOK OF INSECTS. 



PSENID.E 



1. Three complete submarginal cells. Pseninae. Our 

 principal genus is Psen. They nest either in sand or in 

 twigs and provision their nests with Homoptera. 



Two complete submarginal cells. Pemphredoninse. .2. 



2. Eyes large, their inner margins converging above. 

 Plenoculus. Nests in sand. 



Eyes small, inner margins not converging above; 

 head well developed behind the eyes ................... 3. 



3. Only i recurrent vein in front wings ............... 4. 



Two recurrent veins ............................. 5. 



4. Abdomen with a distinct petiole. Stigmus. Our 

 species, americanus, provisions its nests, in branches or 

 stumps, with aphids. 



Abdomen without a petiole. Spilomena; our principal 

 species is pusilla. 



5. Abdomen with a petiole; head and thorax rather 

 hairy. Pemphredon. As far as known, the species 

 prefer to make their nests in decaying wood, provision- 

 ing with aphids. 



Abdomen without a petiole; head and thorax not 

 hairy. Passalocceus. They nest in rotten wood, galleries 

 of wood-boring insects, and hollow plant-stems, provision- 

 ing with aphids and other small insects. 



In Notoglossa emarginata the process on the back of the 

 thorax is broad and slightly forked at the tip. Our 

 other species belong to Oxybelus, the process being acute 

 at the tip. European observations indicate that they nest 

 in sand, provisioning with small flies, w r hich they crush 

 with their mandibles but carry home on their sting. 



CRABRONIDvE 



These wasps are usually much less than half an inch 

 long and black, often marked with yellow. The head is 

 large and rather square-cut. Anacrabro has the abdomen 

 deoressed, flat beneath; the second discoidal cell is much 



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