HYMENOPTERA 935 



size, the largest being only about 12 mm. in length. They can be 



distinguished from other H>-menoptera by the form of the abdomen, 



in which there are at most five and usually 



only three or four exposed segments (Fig. 



1 1 73), and which is strongly concave below, 



so that it can be readily turned under the 



thorax and closely applied to it. In this 



way a cuckoo-wasp rolls itself into a ball 



when attacked leaving only its wings ex- 



P°^^^- . . . ^ _ J 



In this family and in the preceding one p. rj, ' 



the antennce are 13 -segmented in both sexes; nitidula ^^^^^ 



the pronotum does not reach the tegulas; 



there are no closed cells in the hind wings; and the ovipositor is an 

 extensile jointed tube. 



The cuckoo-wasps are so-called because they are parasitic in the 

 nests of solitary wasps and solitary bees. A cuckoo-wasp seeks until 

 it finds a wasp or bee, building its nest, and when the owner of the 

 nest is off collecting provisions steals in and lays its egg, which the 

 unconscious owner walls in with her own egg. Sometimes the cuckoo- 

 wasp larva eats the rightful occupant of the nest, and sometimes 

 starves it by eating up the food provided for it. The bees and 

 wasps know this foe very well, and tender it so warm a reception that 

 the brilliant-coated little rascal has reason enough to double itself up 

 so the righteous sting of its assailant can find no hole in its armor. 

 There is one instance on record where an outraged wasp, unable to 

 sting one of the cuckoo-flies to death, gnawed off her wings and 

 pitched her out on the ground. But the undaunted invader waited 

 until the wasp departed for provisions, and then crawled up the post 

 and laid her egg in the nest before she died. 



A monograph of the North American species was published by 

 Aaron ('85), one of the species of the world by Mocsary ('89), and 

 another by Bischoff ('12). 



The family ANTHOBOSCID^ is represented in North America 

 by a single species, Sierolomorpha amhtgua. This is shining black, 

 with an oval abdomen, the first segment of which is constricted off 

 from the rest. It measures 4.5 to 6 mm. in length. 



Family SAPYGID^ 



The Sapygids 



This is a small family including only three North American 

 genera, and but little more than twenty species. These insects are of 

 moderate size, with short legs, and are usually black, spotted or banded 

 with yellow, rarely entirely black. So far as their habits are known, 

 they are inquilines in the nests of solitary wasps and solitary bees. 



The family THYNNID^ is represented in our fauna by a single 

 rare species of the genus Glyptometopa, found in California. 



