THE INSECT WORLD. 



53 



divided. The new orders are referred to, however, in the proper 

 place. 



Lowest of all are the Thysaiiura, including "bristle-tails," 

 * * spring-tails, " " fish-moths, ' ' and the like. They never become 

 winged or develop even a trace of wings. The mouth parts are 

 small, retracted, usually formed for biting, but sometimes so 

 undeveloped as to be almost without type. The metamorphosis 

 is incomplete ; indeed there is only a simple increase in size, and 

 nothing really worthy of the term development. In most cases 

 the abdomen bears a pair or more appendages at the tip, from 

 which some of the common names are derived. 



Next come the Neuroptera, or nerve-winged insects. These 

 have four well-developed wings, membranous, more or less 

 transparent, and so crossed by numerous veins that they seem 

 reticulated or netted : from which character they derive their 

 name, which means nerve-winged. The mouth parts are man- 

 dibulate, usually well developed, but sometimes almost obsolete. 

 In its broadest sense the order includes "May-flies," "dragon- 

 flies," " caddice-flies," "white ants," "stone-flies," "lace-wing 

 flies," and the like. There are, however, two types of meta- 

 morphosis, — one complete, the Neuroptera proper, and the other 

 incomplete, the Pseudo-neuroptera. It is here that most of the 

 new ordinal divisions have been made. 



A step in advance are the Orthoptera, or straight-winged 

 insects, such as roaches, crickets, katydids, and grasshoppers. 

 They have two pairs of well-developed wings, — the first or ante- 

 rior usually narrow and a little thickened or parchment-like; the 

 second or posterior broader, plaited or folded like a fan beneath 

 the anterior pair. The mouth parts are formed for biting, and the 

 metamorphosis is incomplete. 



The order Hemiptera, or "half-winged" insects, includes all 

 the true ' ' bugs ;' ' and to members of this series only the term 

 "bug" is properly appHed, according to entomological opinion. 

 The order is always distinguishable by the mouth structure, which 

 is haustellate, and consists of a jointed beak, concealing two pairs 

 of slender, pointed lancets. The metamorphosis is incomplete. 

 The term Hemiptera, or ' ' half-winged, ' ' is derived from the fact 

 that in the typical series the primaries are thickened at base and 

 thin or membranous at tip. In it we have such creatures as the 



