I 
C50 
THE STUD Y OF INSECTS. 
Fig. 771 .—Pomfilus, 
Family Pompilid^e (Pom-pil'i-dae). 
The Spider-wasps . 
The spider-wasps are so called because they provision 
their nests with spiders. They are slender in form, with long 
legs (Fig. 771), and are usually black with 
dusky reddish or black wings; sometimes 
they are variegated with red or orange. The 
peduncle is short, so that the abdomen is very 
closely united to the thorax. Many of the 
species are of medium size, but some are very 
large. In fact, the largest of all known Hymenoptera belong 
to this family. 
One of the giants of the family is the well-known Taran¬ 
tula-hawk, Pepsis formosa (Pep'sis for-mo'sa), of the South¬ 
west, which stores its burrows with Tarantulas. Many a 
hard-fought battle does this digger-wasp have with these 
enormous spiders; and sometimes it is conquered and igno- 
miniously eaten. 
Most of the Pompilidae dig burrows in the ground; but 
some species of Agenia (A-ge'ni-a) make cells of mud attached 
to the lower surface of stones or in the chinks of walls; and 
the members of the genus Ceropales (Ce-rop'a-les) are inqui- 
lines in the nests of other digger-wasps. 
About one hundred and twenty species belonging to this 
family are known in our fauna. 
Family SPHECID/E (Sphec'i-dae). 
The Sphecids ( Sphe'cids) or the Thread-waisted Wasps. 
These are the most commonly observed of all our 
digger-wasps, as certain species build their mud nests in the 
attics of our houses • and, too, the peculiar shape of the 
body makes them very conspicuous. The Sphecidae differ 
from the preceding families of digger-wasps in that the pro- 
