494 
Saw-flies, Gall-flies, Ichneumons, 
from the hole the wasp always backs upward out of it and while digging 
keeps up a low humming sound. After the tunnel is dug about three inches 
deep she covers up the mouth with a bit of salt crust or little pebbles, and 
flies away. Some minutes later she comes back carrying a limp inchworm 
about an inch long, which she drags down into the nest. Away she goes 
again and soon returns with another inchworm; repeating the process until 
from five to ten caterpillars have been stored in the tunnel. All these are 
alive, but each has been stung in one of its nerve-centers (ganglia) so that 
it is paralyzed. Finally, down she goes and lays a single egg, attaching 
Fig. 696. 
Fig. 697. 
Fig. 696. —Nest-burrow of Ammophila, with food for the young; paralyzed inch worms 
in bottom and burrow nearly filled. (Natural size.) 
Fig. 697 —Ammophila bringing covering bit of salt incrustation to put over the stored 
and filled nest-burrow. (From life; natural size.) 
it to one of the paralyzed caterpillars. She then fills the tunnel with pellets 
of earth, carefully chewing up the larger pieces so as to make a close, well- 
packed filling. Lastly, she carefully smooths off the surface and puts a 
small flat piece of salt crust on top, so that the site of the tunnel shall be as 
nearly indistinguishable as possible. 
Ammophilas are common all over the country, and the nest-building 
of various species has been watched by other observers. The use by an 
individual Ammophila of a small pebble, held in the jaws, as a tool to pound 
down and smooth off the earth has been twice recorded, once in Wisconsin 
and once in Kansas. These are perhaps our only records of the use of a 
tool by an insect. 
The habits of the Ammophila described above are typical of the interest¬ 
ing life-history which, varying indeed in many details, is common to nearly all 
of the solitary wasps, whether belonging to the Sphecoidea or Vespoidea. 
