20 COLLECTING AND PRESERVING INSECTS. 



Classification of Insects. That branch of the Animal King- 

 dom, known as the Articulata, was so called by Cuvier in his 

 work on the animal kingdom, from having the body composed 

 of rings, like short cylinders, which are placed successively 

 one behind the other. In the class of Worms these rings 

 or segments are arranged in a continuous row, and their num- 

 ber is indefinite. The organs of locomotion consist of tuber- 

 cles bearing bristles placed in a row, one on each side of 

 each ring ; while on the head-rings there are slender feelers 

 directed forwards and placed around the mouth-opening. In 

 the class of Crustacea this continuity of rings is broken, and 

 they for the most part bear hard, jointed appendages ; and 

 there is usually a definite number (20), which are gathered into 

 two regions : the head-thorax and abdomen. In the class of 

 Insects, the number of rings is still more limited (18), the 

 head, consisting of four rings, is distinctly separated from the 

 thorax, thus forming, with the abdomen or hind-body, three 

 distinct regions. 



In the Insects, again, there are three modes of disposing 

 the rings and their appendages : 



1. Where the number of segments is indefinite, and much 

 like each other in form, supporting both thoracic and abdom- 

 inal legs ; as in the order of Myriopoda. 



2. Where the head and thorax are closely united ; and there 

 are four pairs of legs attached to the thorax alone, as in the 

 Arachnida. 



3. Where there are three distinct regions to the body ; the 

 head, thorax and abdomen, as in the Insecta. Moreover, the 

 true insects have three pairs of legs attached to the thorax ; 

 and are, with few exceptions, winged. 



The Myriopods grow by the addition of rings, after hatching 

 from the egg ; the Arachnids by frequent moultings of the 

 skin ; while the winged insects pass through a, distinct meta- 

 morphosis. The young insect after being hatched from the 

 egg is called the larva, from the Latin term meaning a mask, 

 since it was the ancient belief that it concealed beneath its 

 skin the form of the perfect insect. When full-fed the pupa- 

 skin rapidly forms beneath the tegument, and the insect in 

 that form escapes through a slit in the back of the larva. The 

 perfect insect is often called the imago. The larval state of 



