HYMENOPTERA OR BEES, ANTS, WASPS, ETC. 69 



sene, gasoline or bisulphide of carbon. In the south and 

 in California, the Argentine ant which was recently intro- 

 duced from Argentina is proving a serious pest to the 

 fruit growers, and there are several other species which 

 which make themselves more or less of a nuisance. 



The species of ants are very numerous and they are 

 found in nearly all parts of the earth. It would require 

 a volume to treat of the peculiarities of these interesting 

 insects, and we can no more than mention the remarkable 

 honey ants, the harvesting ants, the leaf-cutting and 

 fungus-growing ants, and the ferocious driver ants; all 

 of these it would well repay the student to look up in 

 larger works. 



Besides the ants, bees and wasps, the Hymenoptera in- 

 clude a number of less well-known families. The ich- 

 neumons and their relatives lay their eggs on or in the 

 bodies of insects or insect larvae, and the young feed upon 

 the tissues of their host, thereby proving of great value 

 in checking various insect pests. The members of 

 the family Cynipidae are commonly known as the gall 

 flies. When the eggs of these insects are deposited on 

 or in the tissues of plants a peculiar growth of the vege- 

 table tissue results, which is called a gall. The shapes 

 of these galls are very characteristic; the gall caused by a 

 certain kind of insect in a particular species of plant differs 

 from the gall produced by another insect in the same plant 

 and also from that produced from the same insect in 

 a different kind of plant. Galls may be produced by 

 members of various other families of insects, such as the 

 aphids and certain flies. They represent an abnormal 

 growth of plant tissue caused by the presence of some ir- 

 ritating material, but they are of use to the insects pro- 

 ducing them because they afford both food and shelter 

 for the young. 



