70 Some Solitary Wasps of Texas. 



around these animals themselves ; Bembex helfraegi makes trees and 

 bushes her hunting grounds; leaf-ho])per catchers fly in and out 

 among the grasses in search of food for their young; the cricket- 

 killer Larra runs into and out of holes in the ground or under 

 stones; Microbembex glides gracefully through the woods satisfied 

 with the first insect or part of an insect that comes to view. 



As regards the feeding habits among solitary wasps two types may 

 be recognized: first that in which the growing larva is fed by the 

 mother from day to day until the larval or eating stage has passed 

 and the larva has spun its cocoon and become quiescent; and sec- 

 ond, the type in which the store of food is provided once for all, the 

 egg laid among the provisions, the nest closed over the egg and the 

 larva left to its fate. 



The Peckhams consider the habit of feeding the larva from day to 

 day as the most primitive. They say : "It may be possible then that 

 all wasps originally fed their young as Bembex now does and that 

 while the instinct of storing the whole supply of food once for all 

 was working itself out among solitary wasps, the instincts of life 

 in a true society developed into those of our wasp communities." 

 From this point of view, Microhembex on the one hand and the 

 social wasps on the other show the habit in its most primitive form 

 since they not only feed their larvae until these pupate, but they 

 gather almost any kind of insect food they find. The first step 

 in tlie development among the Digger-wasps would then be the 

 specialization shown in all other wasps of confining themselves to 

 one kind of prey (flies, bugs, caterpillars, as the case may be). In 

 this Bembex and some species of Monedula are most primitive, since 

 they continue to food their larvae from day to day. Finally comes 

 the habit which obtains in nearly all solitary wasps of provisioning 

 the nests once for all. This is shown in its highest form in the 

 Ammophiles and Pompilides, Avhich paralyze the caterpillars and 

 spiders, store them in the nest and lay the egg upon them. In 

 these cases the nest is closed long before the egg is hatched and the 

 mother wasp never sees the larva. There are however, transitional 

 cases between the habits of Bembex and that of Ammophila. Thus 

 Monedula Carolina, the big fly catcher, closes her nest several days 

 before the larva spins its cocoon, after first supplying the larva with 

 a sufficient supply of food. The little bug-catcher Bembidula parata 

 shows a somewhat greater difference, for while she stores her nest as 

 fast as she can with very small bugs, the work is not finished until 



