N 
THe HyMeENopTerA oF MINNESOTA 21 
PSENIDAE 
Antennae inserted near middle of face; mesepisternum with a dorsal and ventral 
plate; abdomen petiolate; wings with three cubital cells. 
This family has the rank of a sub-family (Pseninae, Family 
Sphecidae) in the “Hymenoptera of Connecticut.” 
The family is fairly well represented in Canada and the United 
States. Psen concolor provisions its nest in hollow stems with Psyllids. 
In 1913 Psen (Pemphredon) tenax was reported as attacking roses in 
the Toronto district. 
OXY BELIDAE 
Head transverse; scutelleum margined; post scutellum armed with a spine, thorn 
or forked process and with squamae; front wings with the first discoidal cell oblit- 
erated, rarely distinct, most frequently confluent with the second discoidal cell. 
First cubital and first discoidal cells confluent. Eyes with their inner margins sub- 
parallel. 
These small wasps burrow in 
the sand and provision their 
nests with flies, not stinging 
them, but crushing the thorax 
and thus destroying the princi- 
pal nerve ganglia. The Peck- 
hams found in some of the bur- 
rows of Oxybelus quadrinotatus 
a dozen flies in the same nest, 
all with the thorax crushed. 
We figure O. subulatus as a 
Minnesota species. 
Fig. 105. Oxybelus subulatus Rob. 
CRABRONIDAE 
Head large, quadrate or trapezoidal; scutellum normal, post scutellum unarmed; 
front wings with the first discoidal cell always distinct; front wings with only one 
sub-marginal cell; middle tibia with only one apical spur. Eyes with their inner mar- 
gins strongly converging below. 
Sometimes popularly referred to as “sand wasps.”’ Over cne 
hundred species of this family are known. ‘They exhibit great diver- 
sity of habits. Westwood says, “Those (species) whose economy has 
been clearly traced, make their cells in wood, boring into palings, posts, 
willows, stumps, pithy stems, etc. Their fore feet are well adapted for 
digging and tunneling. Members of this group, like the preceding, 
are said to crush the thorax of their prey, thus paralyzing the chief 
