16 



EXTERNAL STRUCTURE OF INSECTS 



eyes. The metamorphosis is incomplete. The larval or nymph 

 stage is passed in the water (Fig. 15). 



Order Plecoptera. Insects with four membranous wings, hind 



FIG. 13. Ant-lion with larva, enlarged and natural size. 



wings much larger than fore wings, and when not in use folded in 

 plaits. Wings lie flat upon the abdomen when the insect is at rest. 

 Biting mouth parts frequently poorly developed. Metamorphosis 

 incomplete, nymphs living in water. Example, stone flies. 



NA* 



FIG. 14. A caddis-fly, showing c, larva, removed from its case; b, adult; e, pupa. On the 

 right is a case made of stems. 



Order Isoptera. Social insects, colonies including queens, 

 kings, and workers, only the first two casts being winged, and then 

 only temporarily. Mouth parts formed for biting; incomplete 



