USEFUL INSECTS 



357 



Cochineal and Lac. — Among the many products of insect origin 

 is cochineal, a red coloring matter, which consists of the dried 

 bodies of a tiny insect, one of the plant lice which live on the 

 cactus plants in Mexico and Central America. The lac insect, 

 another one of the plant hce, feeds on the juices of certain trees 

 in India and pours out a sub- 

 stance from its body which 

 after treatment forms shellac. 



Gall Insects. — Oak galls, 

 growths caused by the sting of 

 wasp-like insects, give us prod- 

 ucts used in ink making, in 

 tanning, and in making pyro- 

 gallic acid which is much used 

 in developing photographs. 



Other Useful Insects. — 

 We have noted that insects 

 pollinate flowers; that silk- 

 worms spin silk, thus forming 

 material for clothing ; that bees 

 gather honey; that in many 

 cases insects are preyed upon, 

 and supply an enormous mul- 

 titude of birds, fishes, and 

 other animals with food. Dr. 

 Forbes of the University of 



Illinois estimates that many of the smaller fresh-water fishes take 

 from 99% to 52% insect food, mostly larvse. 



The carrion beetles and many water beetles act as scavengers. 

 The sexton beetles bury dead carcasses of animals. Ants in 

 tropical countries are particularly useful as scavengers. 



Some forms of animal life are of great importance because of 

 their destruction of harmful plants and animals. Insects often do 

 a service by eating harmful weeds ; thus many harmful plants are 

 kept in check. The '^adybug," or ladybird beetle, is the natural 

 enemy of the orange tree scale. It may often be found also feed- 

 ing on the plant lice, or aphids, which live on rosebushes. 



A near relative of the bee, called the ichneumon fly, indirectly 



H. NEW CIV, BIOL. — 24 



American Museum of Natural History. 



Pearl shell, and buttons of various sizes 

 cut from pearl shell. 



