TEE INSECTS. 109 



in the sides of the body. There are in many insects two 

 pairs of thoracic and eight pairs of abdominal spiracles. 

 The anatomy of the grasshopper may also be compared 

 with that of the western cricket (Fig. 131). 



The antennse are both organs of touch and also of smell, 

 the olfactory organs being little pits ; some insects, how- 

 ever, hear with their antennae. The locusts have a pair of 

 larga ears situated at the base of the abdomen (Pig. 128). 



Insects produce sounds in various ways, either as in 

 locusts by rubbing the legs against the closed wings, or by 

 rubbing the upper on the under or hind wings; while some 

 insects produce creaking sounds by rubbing the harder 

 parts of the body together. 



In walking or running, an insect, as a beetle (Fig. 132), 

 raises and puts down its six legs alternately, as may be 

 seen by observing the movements of any large insect. 



The wings are broad thin bags or expansions of the skin. 

 They are strengthened by hollow rods called veins, of 

 which there are six principal ones. The veins are hollow, 

 usually containing an air-tube. 



The wing of an insect in making the strokes during flight 

 describes a figure 8 in the air. A fly's wing makes 330 rev- 

 olutions in a second, executing therefore 660 simple oscil- 

 lations. 



According to M. Plateau, who has recently made ingen- 

 ious experiments regarding the strength of insects, the 

 smallest of these animals are iDroportionally the strongest. 

 A cockchafer can pull 31 times more, proportionally, than 

 a horse, while a bee pulls thirty times more. (Tlie ani- 

 mals were attached to a cord passing over a pulley to a 

 weighted scale.) The horse lifts 6-7ths of its weight, the 

 cockchafer 11 times its weight, and the bee 20 times. 



Insects are very prolific, laying hundreds of eggs. Some 

 insects, as the cricket, grasshopper, and ichneumon fly, 

 possess a horny tube called an ovipositor, by means of 

 which they bore into wood or the earth and deposit their 

 eggs one after another. 



