AN INTRODUCTION TO ENTOMOLOGY. 



The principal ones are arranged somewhat like the bars of a fan ; 

 and the wings when not in use are folded in a fan-like manner. The 

 name Orthoptera is given to this order on account of this longitudi- 

 nal folding and position of the second pair of wings when closed. 



There are many wingless genera in the order. A few species have 

 the anterior pair only; and in one instance at least, the first pair are 

 wanting while the second pair are present. 



The mouth parts are all present, and are well developed. The 

 student who wishes to get a clear idea of the structure of a typical 

 insect's mouth cannot do better than to dissect the mouth of a cock- 

 roach or locust. 



The appendages of the abdomen furnish important characters for 



the purposes of classification. Thus the 

 form of the ovipositor is of great ser- 

 vice in distinguishing the families ; and 

 the cerci, a pair of appendages one on 

 each side near the caudal end of the 

 abdomen, are also much used in de- 

 scriptions. 



In the Orthoptera the metamorpho- 

 sis is incomplete. In the case of those 

 species that never acquire wings the 

 change in form from the newly hatched 

 nymph to the adult is frequently in- 

 considerable. With others we see the 

 wings, developed by degrees, as de- 

 scribed in Chapter I. (Figs. 8 to 13). 

 There are many Orthoptera that have in the adult state only 

 rudimentary wings. These resemble very strongly immature insects. 

 It is often important to determine whether a short-winged speci- 

 men is an adult or not ; this is especially true in case of the Acridi- 

 dce, or locusts. Fortunately this determination can easily be made 

 with the Jumping Orthoptera (section Saltatoria). In case of these 

 insects the wing-pads of the nymphs are inverted, as shown by the 

 curving down of the extremities of the wing-veins instead of up, as 

 with the adult ; and the rudimentary wings are outside of the wing- 

 covers, instead of beneath them. There is also the distinction that 

 these rudiments of the second pair of wings are triangular in outline, 

 and are flat, not folded ; while the wings of the adult are more or less 

 folded, even when too small to be of use as organs of flight. 



Certain species belonging to the three higher families, AcridicLx, 



Fig. 83.— Mouth-parts of the Red- 

 legged Locust. 



