INSECTS DIAGRAM G. 



109 



on each side. These are called stigmata, and are the openings for 

 fine vessels filled with air, -which communicate with the exterior 

 by the stigmata. These vessels are called trachecv. They have a 

 fine silvery colour, and nothing is easier than to see them by 

 opening the abdomen of a cockchafer under water, with a little 

 care. All these channels, which look like threads of silver, and 

 which ramify in the middle of the organs of the insect's body, 

 become visible immediately. It breathes by means of these 

 trachea?. 



Insects lay eggs, which are often 

 very- numerous. They take care to 

 deposit them in places where the 

 larvae which will emerge from them 

 will find the means of living. If 

 the larva is aquatic, the insect, 

 though aerial, deposits its eggs in 

 the water. 



Insects, chiefly in consequence of 

 the great appetite of their larva?, 

 are injurious animals ; they are the E gS s of Bu S on a Leaf - 

 scourge of agriculture, and man suffers much more from them than 

 from tigers, lions, or venomous serpents. There are certainly 

 some insects which eat others, and are consequently useful 

 auxiliaries to man ; but there are not very many. And it is on 

 account of the devastation of insects that all the insectivorous 

 mammals and birds ought to be considered as the greatest friends 

 of agriculturists. Some insects, however, must be mentioned 

 which, like the bee, the silkworm, and the cochineal, are directly 

 useful to man, but these are exceptions. 



Insects are divided into several orders, which are characterized 

 either by the structure of the mouth, or by the number and 

 texture of their wings. We shall mention each of them, and 

 state their distinguishing characters. 



