10 



female is furnished at the tip of the abdomen with four very short corneous 

 pieces, two of which curve upward and two downwaixl This family includes 

 the locusts of the eastern continent (the seventeen-year locust of the United 

 States is a very different insect, "belonging to an entirely ditferent order). The 

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

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

 hopper of the West is another. 



The Acrididse undergo an imperfect metamorphosis ; that is to say, the 

 larvaa and pupae resemble the perfect insects, except in size and in the devel- 

 opment of the wings. This is also true of all orthopterous insects, and forms 

 one of the characteristics of the order. 



THE EXTERNAL STRUCTURE AND TERMINOLOGY. 



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 wings 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 tiji of the 

 abdomen the extreme posterior. 'Anterior" or " before ""will then signify 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 consid- 

 ered 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 dor- 

 sum of the pronotum 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 cannot be introduced. This idea is to be 

 retained throughout, even in describing the separate parts ; thus, we speak of 

 the dorsum or back and sides of the head, the dorsum of the thorax, &c. 

 "Longitudinally'' and "length'' will then signify in the direction of the length 

 of the- body ; "transverse" and "width,'' from side to side; "height "and 

 "depth," up and down. It may appear useless to add such explanations as 



