INTERNAL STRUCTURE. 



Fig. 4.2. — Earl J' 

 Mountain Locust. 



stages of Rock}- 

 After Rilev. 



nymph or pupa is as active 

 and hungry as the imago, and 

 differs from it only by possess- 

 ing but rudimentary^ wings 

 and genitalia. The latter are, 

 however, in some cases suf- 

 ficiently developed to permit 

 coition. In cases where the 

 species is alwaj^s wingless the differences, except in size, be- 

 tween a newly hatched and a mature insect are sometimes 

 very slight. Other species have in the adult stage only 

 rudimentary wings and thus they resemble the pupal stage. 

 It is, however, always easy to determine whether such an 

 insect is an adult or not, as the wing-pads in the nymph are 

 twisted in such a manner that, when closed, the\^ are re- 

 versed and the inner surface in the imago is the outer sur- 

 face in the pupa ; the rudimentary lower wings are outside 

 of the upper ones, instead of beneath. A trained eye can 

 detect many other differences. The sexual characters are 

 not well marked in the younger or first three stages; later 

 the differences become apparent. Orthoptera being like all 

 other insects enclosed in a rigid armor of a substance that 

 will neither stretch nor grow, have to shed this skin from 

 time to time. A locust, when ready to do so, quits feeding 

 for a time and remains inactive during the process. In the 

 First Annual Report of the U.S. Entomological Commission 

 the following description is given of the last molt — from the 

 pupa to the winged insect. 



"When about to acquire wings the pupa crawls up some 

 post, weed, grass-stalk, or other object, and clutches such 

 object securely with the hind feet, which are drawn up under 

 the body. In doing so the favorite position is with the 

 head downward, though this is by no means essential. Re- 

 maining motionless in this position for several hours, with 

 antennae drawn down over the face, and the whole aspect 

 betokening helplessness, the thorax, especially the wing- 



