224 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
PEMPHREDONIDAE 
Eyes normal, not emarginate within; ocelli distinct; labrum most frequently 
hidden; front wings with two submarginal cells: middle tibia with only one apical 
spur; abdomen sessile or petiolate, without a constriction between the first and second 
segments. (Listed as a sub-family in Hym. of Conn.) 
These are rather small, slender 
wasps, of a shiny black color, which 
burrow in pith of dry branches, mak- 
ing very irregular and complicated 
channels. They. frequently store 
their nests with plant lice. 
Pemphredon tenax Fox. occurs in 
Minnesota, and Stigmus sp. has been 
taken in St. Louis Co. in August. 
Fig. 118. Pemphredon tenax Fox, 
female. 
BEMBICIDAE 
Antennae inserted close to eclypeus; cheeks narrow, prepectus wanting; eyes 
normal, not emarginate within; ocelli aborted, represented by sears; labrum large, 
free, well developed, much longer than wide, triangularly elongated: front wings with 
three submarginal cells; abdomen sessile, never petiolate, no strong constriction be- 
tween first and second segments; otherwise as in Sphecidae. 
These wasps nest in the ground, frequently in colonies, and provi- 
sion their nests with Diptera or Hemiptera. The biology of this group, 
particularly of Bembe.x, has been treated by various observers. An ex- 
tremely interesting account of Bembex occurs in Fabre’s “The Hunt- 
ing Wasps.” To the question as to why Bembex does not paralyze her 
prey by stinging, Fabre replies that her abdomen is so formed that 
shevcannotdo-so. Parker (Proc. U.S. Nat.’ Mus; Vol, 52 -pi2snee 
seq.) discusses at length the biology of the Bemicidae and in the course 
of his remarks states his belief that a Bembicid wasp finds her skill- 
fully concealed burrow by the sense of smell, citing several instances 
where he greatly disturbed the surface over the burrow, even to the 
extent of dashing water over it, but never succeeded in confusing the 
female wasp. 
A prominent member of this family is Sphecius speciosus Say, the 
giant sand wasp or “cicada killer,’ which provisions its burrows 
with different species of Cicadas. A Florida species preys upon the 
large horse fly Tabanus atratus. Coquillet reported frequently ob- 
serving, in California, Bembex fasciata storing its nest with Eristalis 
tenax and other flies. Members of the genus Stizus (large hairy 
bodied wasps) paralyze grasshoppers and other large insects (in- 
cluding the dog-day cicada) and carry them off to their burrows. 
