242 



THE INSECTS 



larvse of which feeds on j'oung wheat ; the botfly, which in a 

 larval state is a parasite on horses ; the dreaded tsetse fly of South 

 Africa, v;hich causes disease in horses and cattle by means of the 

 transference of a parasitic protozoan, much like that which causes 

 malaria in man ; and many others. 



Among the few flies useful to man may be mentioned the tachina 

 flies, the larv£E of which feed on the cutworm, the army worm, 

 and various other kinds of injurious caterpillars. 



Characters of the Diptera. — Members of this group have only 

 one pair of wings; the mouth parts are fitted for sucking, rasping, 

 or piercing, and they pass through a com- 

 plete metamorphosis. 



Coleoptera. Beetles. — Beetles are the most 

 widely distributed and among the most nu- 

 merous of all insects. There are over one 

 hundred thousand Uving species. 



Any beetle will show the following charac- 

 teristics : (1) The body is usually heavy and 

 broad. Its exoskeleton is hard and tough, the 

 ehitinous body covering being better developed 

 in the beetles than in any other of the insects. 

 (2) The three pairs of legs are stout and rather 

 short. (3) The outer wings are hard and fit 

 over the under wings like a shield. These 

 sheathlike wings are called elytra. (4) The 

 mouth parts, provided with an upper and lower 

 lip, are fitted for biting. They consist of 

 very heavy curved pincher-shaped mandibles, which are provided with 

 palps. 



The Life History of a Beetle. — The June beetle (May beetle) and potato 

 beetle are excellent examples. May beetles lay their eggs in the ground, 

 where they hatch into cream-eolored grubs. A grub differs from the larva 

 fly or maggot in possessing three pairs of legs. These grubs Uve in bur- 

 rows in the ground. Here they feed on the roots of grass and garden 

 plants. The larval form remains underground for from two to three years, 

 the latter part of this time as an inactive pupa. During the latter stage 

 it lies dormant in an ovoid area excavated by it. Eventually the wings 

 (which are budlike in the pupa) grow larger, and the adult beetle emerges 

 fitted for its life in the open air. 



Order Hemiptera. Bugs. Characteristics. — The cicada, or, as it is 

 incorrectly called, the locust, is a familiar insect to all. Its droning song 

 is one of the accompaniments of a hot day. The song of the cicada is 



Stag beetle: u, antenna; e, 

 eye ; m, mandible ; p, pal- 

 pus. Photograph one half 

 natural size. 



