122 ARTHKOPODA 



that of the Coleoptera, a grub; that of the Diptera, a 

 maggot. The larva of some families has as many as six- 

 teen legs, while in others there are from six to twelve, and 

 in the weevils no legs are present. 



As the structure of the various insects is so similar, a 



FIG. 143. Diagrammatic cross section of a grasshopper enlarged three times ; h, 

 chief blood vessel ; i, intestine ; , ganglion of the nerve cord ; t, stigmata or 

 spiracle for the admission of air to the branched tracheal tubes ; w, wings ; a, 

 coxa ; ft, trochanter ; c, femur ; d, tibia ; e, tarsus. 



study of any form will serve to give a general knowledge 

 of the anatomy of all. Large locusts or grasshoppers are 

 easily secured, and can be dissected to advantage if pre- 

 served in seventy per cent alcohol (commercial alcohol 

 three parts and water one part). To dissect, place in a pan 

 with water sufficient to cover and fix to the wax-covered 



