i8o ELEMENTARY ZOOLOGY 



distinct regions such as crop, proventriculus, stomach, 

 intestine, etc. ? How is it held in place ? Trace the 

 principal longitudinal trachea! trunks. Find, if you can, 

 a pair of small compact bodies usually somewhat elongate, 

 one lying on each side of the posterior part of the alimen- 

 tary canal. These are the rudimentary reproductive 

 organs. 



Remove the alimentary canal by cutting it off at its 

 posterior tip and also in the prothoracic segment. Work 

 out now the ventral nerve-cord and ganglia, and the 

 supra-asophageal (brain) and infra-oesophageal ganglia 

 and the commissures in the head. 



In the body of the caterpillar we have found the same 

 general disposition of organs as in the body of an adult 

 insect, but several differences are nevertheless noticeable, 

 viz., the presence of a large quantity of fatty tissue, the 

 great size and simple character of the alimentary canal, 

 and the undeveloped condition of the reproductive organs. 



OTHER INSECTS 



The class Insecta includes those Arthropods which 

 have one pair of antennae (sense appendages), three pairs 

 of mouth-parts (oral appendages), and three pairs of legs 

 (locomotory appendages). The insects, in further con- 

 tradistinction to the crustaceans, are mostly land animals 

 and breathe by means of tracheae or tracheal gills. They 

 are the most familiar of land invertebrates, and, as already 

 mentioned, include more species than are comprised in all 

 the other groups of animals taken together. Beetles, 

 moths and butterflies, flies, wasps and bees, dragonflies 

 and grasshoppers are familiar members of the class of 

 insects, but spiders, mites, scorpions, centipeds and 

 thousand-legged worms are not true insects and should 



