Wasps, Bees, and Ants 



501 



to its prey by its shrill singing, pounces upon a cicada, paralyzes it by a swift 

 stab, and then laboriously flies with or drags the heavy body to the burrow. 

 This burrow may be a foot or even more in depth, usually consisting of a 

 nearly vertical tunnel for 6 inches, with a sharply diverging nearly horizontal 

 part as long as or longer than the entrance one. Sometimes instead of a single 

 terminal cell there are several lateral cells, in each of which one or two cica- 

 das are stored. Another familiar group of diggers are the spider-wasps, 

 Pompilidae, mostly black or steely-blue with bluish or light-bronzy wings 

 (PL XII, Fig. 13). This is a large family including a few guest-wasps 

 (Ceropales) and a few mud-daubers or mason-wasps (Agenia), as well as 

 true diggers, but all of the members of the family which make their own 

 nests provision them with spiders. The giant tarantula-killer, Pepsis for- 

 mosa (Fig. 704), largest of all our wasps, belongs to this family. It is common 

 in California and the southwest, where its sensational combats with the great 

 hairy tarantulas (Mygale) are often seen. It does not always come off vic- 

 tor in these fights, or at least conquers the tarantula only at the expense 

 of its own life. After one such long and fierce battle I found both fighters 

 hors du combat, the tarantula paralyzed by the wasp's sting, but the wasp 

 dying from the poisonous wounds made by the great fangs of the spider. 



It is a matter of much speculation how the digger-wasps find their nests 

 again after carefully covering them and going off to search for caterpillars, 

 spiders, bugs, or whatever are to be stored up for the larvae. The Peck- 

 hams have made many interesting observations touching the problem, trac- 

 ing carefully the movements (Figs. 705 and 706) and behavior of individuals 



FIG. 705. 



FIG. 705. Locality study of Cerceris deserta, 

 FIG. 706. Locality study of Cerceris deserta. 



J 

 FIG. 706. 

 (After Peckham.) 

 (After Peckham.) 



after finishing a burrow and making ready to provision it. From these 

 observations they conclude "that wasps are guided in their movements by 

 their memory of localities. They go from place to place quite readily because 



