ARTHROPOD A 197 



form a gall. The giant oak-gall grows to the size of the human fist. 



The Ichneumonoidae are parasitic hymenoptera attacking many- 

 injurious insects such as the cabbage butterfly, tent-caterpillars, 

 cotton-worms, brown-tail and tussock moths. 



The braconid flies {Braconidae) are also valuable in that they 

 parasitize plant lice, tomato worms, sphinx caterpillars and fall 

 web-worms. The Serphoidea are a group of mostly small insects 

 parasitic on other insects. 



In the stinging hymenoptera, which include the ants, bees and 

 wasps, the females and workers sometimes have the ovipositor 

 developed into a " sting." 



Ants. {Fo7-micoidea.) — Found in nearly all parts of the world, 

 and comprising some twenty-five hundred species, ants have de- 

 veloped to a marked degree a differentiation in body structure and in 

 habits. The first two segments of the abdomen are expanded dor- 

 sally, serving as a peduncle to the rest of the abdomen. The nest 

 or home, usually underground, is divided into many channels and 

 passages. 



The carpenter ant {Camponotus penn) builds its nest in the dead 

 wood of living trees and of buildings. The mound building a?jt 

 builds ant hills ten feet in diameter. The slave making ants {Formica 

 difficilis) depend on their servants (other ants) for shelter and food. 

 (See Communities, p. 484.) 



The corn louse ant {Lasius brunneus) tenderly cares for one of the 

 extremely injurious aphids attacking the roots of corn. The tiny 

 red ant {Myrmicidae) , while something of a pest in this country, 

 becomes an actual menace in the Orient. 



Stingless ants, the Campanothinae, are provided with a cushion- 

 like poison apparatus and secrete formic acid. Males do not possess 

 a poison. 



Wasps. — The digger wasps {Sphecoidea) are distinguished from 

 the true wasps by their non-folded wings. They are solitary and 

 place paralyzed insects and spiders in their nests, where the larvae 

 feed on living helpless prey. 



The true wasps ( Vespoidea) include the solitary wasps and the 

 social wasps. The solitary wasps {Eumenidae) resemble the digger 

 wasps in that they form burrows. They deposit their eggs and then 

 abandon them. (Consult Taylor, L . H., 1922, Psyche, vol. 29, 

 no. 2.) The social wasps ( Vespidae) include t\v^ yellow jackets and 

 hornets. The queens have stings but the males are harmless. Social 



