152 PRACTICAL ENTOMOLOGY. 



is scarcely a leaf, twig, plant or animal that is not the dwelling 

 place of, and is not preyed upon by some insect. The depredations 

 committed annually by either the wheat midge, apple tree borer, or 

 locust are sufficient evidence of the importance of a study that has 

 for its principal object, the attainment of knowledge which shall 

 assist in preventing their ravages, or counteracting their influence. 



Descriptions and Classifications. 



Entomology {^Entomon, an insect, logos, a discourse,) is that 

 department of Natural History which treats of insects. Insects are 

 animals without backbones, and are therefore termed invertebrates. 

 Their chief character consists in the threefold division of their bod- 

 ies, which are composed of ten jointed rings or sections. Each per- 

 fect insect has at least six legs and feet. The different portions of 

 the body of the perfect insect are the head, which is furnished with 

 two antennae or feelers, and a pair of compound immovable eyes, 

 the thorax, to which are appended the legs and wings and the abdo- 

 men, which generally contains the respiratory system. They attain 

 their perfect or adult state through a series of changes or transfor- 

 mations termed metamorpltoscs, viz : first the egfr, second the 

 larva, third the j^upu or chrysalis, and fourth the imago or perfect 

 insect : from the egg hatches a small maggot or caterpillar of quick 

 growth, which, after a period, casts its skin and enters into the pupa 

 state, when it is covered with a hard substance and without motion ; 

 then after another period throws off this covering and comes forth 

 a perfectly developed insect, which deposits eggs tliat again pass 

 through the same changes. Insects have been divided into seven 

 orders or classes based on the construction and number of their 

 wings. The primary divisions arc termed orders, which are di- 

 vided into sections, the sections into families, families into genera, 

 and genera into species or individuals. The following are the prin- 

 pal orders with descriptions, and notice of some insects of each order 

 for reference and comparison. 



Order I. Coleoptcra {Koleas, a sheath, jdera, wings) The 

 beetle tribe ; four wings, outer ones hard, for" protection ; inner ones 

 transparent, for flight, see figs. 2 and 4. Among the individu- 

 als of this order arc the apple tree borer. May beetle, turnip beetle, 

 wheat weevil, &c. It is in the larva or worm state the insects of 



