19 



second angle, which enables the insect to draw the tibia upward into the 

 channel of the femur. 



The posterior tibiae are furnished at the apex with about four strong 

 spines, pointing downward, to give secure footing in leaping. The posterior 

 face is furnished for about two-thirds of its length from the apex with two 

 rows of spines, one row on each margin. 



The organs of flight consist of two upper wings, elytra^* and two under 

 wings, to which the name wings (alse) is usually applied. 



The elytra (Fig. 1, el) are generally in the form of an elongate oval, or 

 an elongate parallelogram narrowed at the base and rounded at the apex. In 

 the perfect insect they usually reach to or extend beyond the tip of the 

 abdomen; but there are numerous exceptions to this rule, in many species 

 being much shorter than the abdomen, and in a few wholly wanting. When 

 the elytra are absent, the wings are also absent. When folded and at rest a 

 portion lies horizontally upon the back, the remainder and much the larger 

 portion being deflexed vertically against the sides of the abdomen. The 

 upper edge, which forms the margin of the suture along the back when they 

 are closed, is usually termed the posterior or anal margin by most authors, as 

 they consider them spread; but I usually employ the word "upper" in allud- 

 ing to this portion, as I consider them closed when describing them. I also 

 usually call the opposite edge the lotoer margin — by most authors named the 

 costal or anterior margin. The area of each elytron is divided into three fields 

 by two strong longitudinal nerves; the larger of these nerves (or veins, as they 

 are sometimes called), which runs a little distance from and sub-parallel to the 

 anterior or lower margin, is the extenio-median nerve; the other, which runs 

 from near the middle of the base obliquely upward toward the posterior or 

 upper margin, usually reaching it a little beyond the middle, is the interno- 

 median nerve. The three fields into which the area is divided have received 

 different names in order to designate them without circumlocution: The 

 anal, posterior, or upper field is the portion between the interno-median nerve 

 and upper margin, and rests horizontally on the abdomen when the elytra are 

 closed. The anterior, marginal, or loicer field is the portion between the 

 externo-median nerve and lower margin, being the lower area on the side 

 when the elytra are closed. The discoidal, intermediate, or middle field is the 

 space between the two nerves mentioned ; it is very often referred to simply 



*By some authors these are termed hemelytra, by others tcgmina. Walker usually 

 calls them forcwimja. 



