370 THE STUDY OF INSECTS 



Family Dryinid^e 

 The Dryinids 



This family is composed of small parasitic wasps of remarkable habits; 

 it is widely distributed over the world and is represented in our fauna by 

 many genera. 



The fore wings have a lanceolate or ovate stigma; the hind wings are 

 without closed cells; the antennae consist of ten segments, the anterior 

 tarsi of the female are usually chelate. The females of the genus Gonato- 

 pus are wingless, ant-like, and are without a scutellum. 



These parasites confine their attacks to the homopterous insects 

 belonging principally to the families, Fulgoridae, Membracidae, and 

 Cicadellidae. 



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 com- 

 posed of molted skins. Here it remains, with its head in the opening in 

 the body -wall of its host, until it has completed 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 larval sac or of round patches of 

 epidermis stripped off from the leaf surface. 



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. All members 

 of the Sphecidae 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 Sphecidae, 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 mem- 

 bers 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 requires 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. 



Only a few of the more common members of the family can be dis- 



