286 



MANUAL OF ELEMENTARY ZOOLOGY 



of cells, known as imaginal discs, which have retained the 

 embryonic power of growing into new organs. The larvae 

 of insects differ greatly. They may resemble the imago 

 in the general shape of the body, as in dragonflies and 



some beetles, or they may 

 be caterpillar-like and have 

 the thorax ill-marked, as in 

 butterflies, sawflies, etc., 

 or they may be mere 

 grabs, as in many flies, 

 bees, etc. 



According to these and 

 other characters the prin- 

 cipal kinds of insects may 

 be classified as follows : — 

 i. Orthoptera. — Jaws 

 adapted for biting, wings 

 usually unlike. Metamor- 

 phosis incomplete. Cock- 

 roaches, Grasshoppers, 

 etc. 



2. Neuroptera. — Jaws 

 either for biting or for 

 sucking. Wings alike, 

 membranous. Metamor- 

 phosis various. Ant-lions, 

 Dragonflies, Mayflies, etc. 



3. Coleoptera. — Jaws for 

 biting. First pair of wings 

 form a hard cover for the 

 membranous second pair. 

 Metamorphosis complete. 

 Beetles. 



4. Hymenoptera. — Jaws 

 for biting and sucking. 



Four membranous wings. Metamorphosis complete. Many 

 live in communities, the majority of the members of which 

 are sterile females or " workers." Bees, Wasps, Ants, Saw- 

 flies, Ichneumon flies. The latter lay their eggs in the larvse 

 of other insects, especially caterpillars. The ichneumon 

 larvae live upon the bodies of their hosts till the latter are 



Fig. 192. — The head and mouth- 

 parts of a bee. — After 

 Cheshire. 



u. t Antenna ; m. t mandible ; g. t labrum 

 or epipharynx ; mx.p., rudiment 

 of maxillary p..lp ; mx., lamina of 

 maxilla ; ip. t Ubial palp ; L, ligula ; 

 b., bouton at end. The paraglossae 

 lie conceal d between the basal 



fiortions of ibe labial palps and the 

 igula, opposite the letters/^. 



