962 AN INTRODUCTION TO ENTOMOLOGY 



The female dryinid seizes her victim with her raptorial fore legs; 

 one pair of pincers usually grips the neck of the prey, the other pair 

 grips the abdomen towards the apex or the hind legs. The wasp 

 then inserts her egg into the body of the bug. A few days later the 

 immature larva of the parasite appears outside the body of its host 

 enclosed in a sac composed of molted skins. Here it remains, with its 

 head in the opening in the body-wall of its host, until it has com- 

 pleted its growth. It then leaves its host and spins a silken cocoon, 

 which in some cases is furnished with an outer covering formed of 

 the lan'al sac or of round patches of epidermis stripped off from the 

 leaf surface. 



A detailed account of the habits of these remarkable insects is 

 given by Perkins ('05) and the family Dryinidas was monographed 

 by Kieffer ('07), and Kiefifer ('14) in a paper on the Bethylidse. 



Family SPHECID^ 

 The Typical Sphecoid Wasps 



In this family the hind wings have an anal lobe and some closed 

 cells ; the abdomen of the male has seven exposed tergites ; the sting 

 of the female is not enclosed by the hypopygium ; the posterior meta- 

 tarsi are not dilated as in the bees and there are no plumose hairs. 

 All members of the Sphecidas are winged. 



To this family belong all of our common nest-building sphecoid 

 wasps. These differ from the bees in that they provision their nests 

 with animal food, insects or spiders, which they have paralyzed by 

 stinging them. Different members of the family differ greatly in 

 their nesting habits; some are mason-wasps, building cells of earth; 

 many burrow in the ground ; and others burrow in the stalks of pithy 

 plants or make use of cavities that they find. 



Most members of the Sphecidce, after preparing their nest, rapidly 

 accumulate an amount of prey sufficient to enable the young to 

 develop to maturity, lay an egg with it, and then close the cell before 

 the egg has hatched. This method is termed mass provisioning. 

 But certain members of the family, Bembex and some others, feed 

 their young from day to day as long as they remain in the larval state. 

 This method is termed progressive provisioning. As each larva re- 

 quires constant attention for a considerable time only a few young 

 can be reared by a single female in this way. 



Many of these wasps after stinging their prey and before placing 

 it in their nest malaxate {i. e. chew) its neck or some other part of 

 the body and lap up the exuding juices. 



The family Sphecidae is divided into six subfamilies, some of 

 which include two or more quite distinct groups of genera or tribes. 

 As many of these tribes are given subfamily rank by some writers 

 each of those represented in our fauna is defined below. These 

 tribes can be separated by the following key, which has been kindly 

 prepared for me by Professor J, Chester Bradley. 



