356 



THE STUDY OF INSECTS 



599. — Chrysis nitidula. 



Family Chrysjdid^ 



The Cuckoo-wasps 



The cuckoo-wasps are wonderfully beautiful creatures, being usually 

 a brilliant metallic green in color. The species are of moderate size, the 

 largest being only about \ of an inch in length. 

 They can be distinguished from other Hymenoptera 

 by the form of the abdomen, in which there are 

 at most five and usually only three or four exposed 

 segments (Fig. 599), 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 exposed. 

 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 assail- 

 ant 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 un- 

 daunted invader waited until the wasp departed for provisions, and then 

 crawled up the post and laid her egg in the nest before she died. 



Family Tiphiids 

 The Tiphiids 



The tiphiids are mentioned mainly because of the species, Tiphia 

 inornata, which is parasitic on white grubs, the larvae of May-beetles. In 

 order to reach the grubs, the wasp has to burrow into the soil until she 

 finds her victim which she seizes with her mandibles and stings it in 

 order to quiet its struggles. She then lays an egg on 

 the back of the grub. The egg hatches and the larva 

 eventually destroys its host. 



The female tiphia is a black shining wasp about 

 one-half an inch in length (Fig. 6qo) . The male is smaller 

 and has an upward projecting spine near the tip of the 

 abdomen. 



Fig. foo. — Tiphia 

 inornaia. 



Family Mutillid^ 



The Velvet-ants 



These handsome insects resemble ants in the general form of the body, 

 but lack the scale-like knot of the pedicel of the abdomen characteristic 



