4 METHODS OF INSECT LIFE. 



Next — Insects breathe by means of tvachece. Thesa 

 tracheai are air-tubes commiinicatiLig with the air by 



Fig. 4. — Yellow Underwing Moth : 1, caterijillar ; 2, chrysalis ; 

 3, moth. 



means of small ojDenings or months of various shapes^ 

 called spiracles,^ because through them respiration, or 

 breathing, is carried on. They are generally placed 

 at regular distances along the side of the insect. Fig. 

 4 shows the spiracles on the sides of the caterpillar 

 and chrysalis of the Yellow Underwing Moth ; but 

 sometimes, especially in the case of Fly maggots, 

 which live in putrid mntter or wet places, the spiracles 

 are at the end of the tail. 



Of this the accompanying figure of the breathing- 

 tubes of the Warble Fly maggot (Fig. 5) is a good 

 example. The tubes carry the air through the maggot, 

 and the spiracles, when a little pressed out at the tip 

 of the tail, are the little black spots so easily obser- 

 vable on maggots in warble-swellings on the backs of 

 cattle. • Thus the maggot can live in the moisture 

 that suits it, and yet draw in air by means of the 

 exposed tip of the tail. Spiracles (or stigmata as they 

 are sometimes called) are of very various shapes, from 



* From Spiro, I breatlie. 



