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. 



