CLASSIFICATION AND GENERAL ORGANIZATION 373 



Order 3, Orthoptera. — The locusts and related forms such as 

 the long-horned grasshoppers, katydids (Fig. 191), crickets, cock- 

 roaches, and walking sticks are here included. Mouth parts man- 

 dibulate. Two pairs of wings, with the anterior pair usually 

 modified by thickening. Development so direct that the term 

 metamorphosis is hardly applicable, although it is sometimes 

 referred to as " incomplete metamorphosis." Species 10,000. 



Fig. 191. — A katydid, Microcentrum rhombifolium, one of the Order Orthoptera. 



The openings of the auditory organs are seen on the second segment of each anterior 

 thoracic appendage (cf. Fig. 1S5, p. 36H;. (From a sketch by Bruce Horsfall, in Xatural 

 History, Vol. XXV, courtesy American Museum of Natural History and Ulric Dahlgreii.) 



Order 4, Platyptera. — The so-called " white ants," or termites, 

 which are not true ants, are the most famihar examples. Mouth 

 parts mandibulate and relatively simple. Wings, if present, two 

 pairs and membranous. Development direct. Species 225. 



Order 5, Plecoptera. — The stone-flies. Mouth parts mandibu- 

 late. Wings, two pairs, membranous and coarsely veined. Devel- 

 opment is direct; the eggs are laid in water and the larvae develop 

 there until the last molt, when the wings are fully formed and the 

 adult insect takes to the air. Species 200. 



Order 6, Ephemerida. — The may-flies (Fig. 193), like the 

 Plecoptera, lay their eggs in water, but the larval life is so pro- 

 longed that the adult flies may live but a day, hence the name 

 Ephemerida. Mouth parts mandibulate in larva but degenerate 



