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THE YOUNG NATURALIST. 



LMay, 



overlying or adjacent to the organs of reproduction, the posterior or 

 hind margin. The angle included between the interior and posterior 

 margins is appropriately called the anal angle. The positions of the 

 nervures in every case give them the names they bear. Thus, the 

 stout thick nervure immediately beneath or upon the anterior margin 

 is the costal nervure, and the one under that again and often nearly 

 parallel to it, the sub-costal nervure : the two enclose a costal cell. The 

 middle ray of the wing, running from the base towards a central point 

 in the hind margin, is the median nervure, but is recurved, and meets 

 the sub-costal ray at a spot about half its length, and thus isolates a 

 large, triangular space, known as the discoidal cell. This cell encloses 

 the orbicular spot, so familiar to lepidopterist ; while the uniform rests 

 upon what may be considered as the continuation of the median ner- 

 vure just before it joins the sub-costal. The last of the principal 

 branches, the sub-median nervure, runs from the base to the anal angle, 

 and encloses, with the interior margin, the anal cell. The median and 

 sub-median nervures are often bridged together by a short ray meeting 

 each at a point one-third of its length from the base, to this the name 

 of intemo median nervure has been given. 



There only remains to mention the inferior rays passing from the 

 median nervure to the posterior margin. Those underlying the sub- 

 costal nervure being termed sub-costal nervules and enclosing sub- 

 marginal cells : the remainder chiefly median and sub -median nervules. 



Most of the above are reproduced, and may be readily traced in 

 the posterior wings. 



The front, or anterior pair, are not always fitted for flight, being 

 sometimes hard and horny, and used to protect the posterior or hinder 

 pair : they are then termed elytra. Sometimes they are of large size 

 and thickly reticulated, of the consistence of parchment, and not much 

 resembling the wings they cover. The term tegmina in this case is 

 appropriately applied. 



In one curious order the fofe-wings are absent, being represented 

 by small twisted appendages, termed pseudo halteres. Again, we find 

 all four wings present, but none of them fit for flight, and another and 

 very extensive order possesses the anterior wings, the hindermost 

 being transformed into halteres. 



Some two-winged insects have the basal part of the anterior wing 

 provided with small membranous appendages of a similar nature to 

 the rest of the wing, and known by the name of alula or winglets. 

 When the wings are of almost equal size, it will be observed that those 

 segments bearing them, viz. : the meso and meta-thoraces, are of equal 



