254 Introduction to the Synopsis of the Acrididce. 



and are distinguished fi-om the Locastidcc by the following characters : 

 The antennas are comparatively short, never exceeding the body in 

 length, and composed of from fifteen to twenty-five joints ; thetarsi 

 are three jointed ; the fem.ale is furnished at the tip of the abdomen 

 with four very short, corneous pieces, two of which curve upward and 

 two downward. This family includes the locusts of the eastej-n con- 

 tinent (the seventeen-year locust of the United States is a very ditfer- 

 ent insect, belonging to an entirely different, order). The common, 

 red-legged grasshopper, which often does much injury to the crops ifi 

 the States, is a familiar example of this family, and the destructive 

 grasshopper of the West is anotlier. 



The Acrididce undergo an imperfect metaraorphpsis ; that is to say 

 the larviB and pupce resemble the perfect insects, except in size and in 

 the development of the wings. This is also true of all orthopterous 

 insects, and forms one of the characteristics of the order. 



Tlie External Structure and Tenninologij. — In describing the insect 

 it is to be understood as in its natural position — on its feet — the front 

 legs standing forward, the middle and posterior ones backward, and 

 the Avings closed. As a matter of course, to examine the wings we 

 must spread them, and to see the under side of the insect we must 

 reverse it ; but the rule applies to the relative position of the parts 

 described. The vertex of the head is considered the extreme front, 

 and the tip of the abdomen the extreme posterior. "Anterior," or 

 " before," will then signity in the direction of the front of the head : 

 "posterior," or "behind," the opposite direction; "above," toward 

 the upper surface or back; and "beneath," or "below," toward the 

 under surface. The entire external surface is considered as divided 

 into four planes, reaching from one extremity to the other, as follows : 

 The "back," or "dorsum," which is the upper surface, horizontal ; 

 the "under," or "ventral, "surface, also horizontal, and the "sides" as 

 vertical planes. 



It is true there are wide variations from this theoretical form, espe- 

 cially in those species which approach a cylindrical shape, or where 

 the dorsum of the promotum is raised into a high, sharp crest ; yet, by 

 retaining the idea of this theoretical form the shape and position of the 

 parts may be more easily understood where figures can not be intro- 

 duced. This idea is to be retained thi-oughout, even in describing the 

 separate |)arts ; thus, w^e speak of the dorsum or back and sides of the 

 head, the dorsum of the thorax, etc. "Longitudinally" and "length" 

 will then signify in the length of the direction of the body ; " trans- 

 verse" and "width," from side to side; "height" and "depth," up 

 and down. It may appear useless to add such explanations as these, 



