194 



THE STUDY OF INSECTS 



Suborder FRENAT^ 



The members of the Frenatae arc most easily recognized by the fact 

 thai the venation of the hind wings (lifters markedly from that of the 

 fore wings, being much more reduced. In this suborder, vein Ri of the 

 hind wings coalesces with subcosta, the two appearing as a single vein, 

 except that, in some cases, a short section of the base of Ri is distinct 



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Fig. 334. — Wings of Prionoxyslus robinicB. 



presenting the appearance of a cross-vein between radius and subcosta 

 (Fig. 334. Ri)-. 



The essential characteristic of the Frenatas is that they are de- 

 scendants of those primitive Lepidoptera in which the two wings of each 

 side were united by a frenulum. This fact should be clearly understood, 

 for in many of the Frenatas the frenulum has been lost. The loss of the 

 frenulum in these cases is due to its having been supplanted by a substi- 

 tute for it, by an enlarged humeral area of the hind wings, which causes 

 the two wings of each side to overlap to a great extent. This overlapping 

 of the two wings insures their synchronous action; and the frenulum, 

 being no longer needed for this purpose, is lost. 



As a rule the frenulum of the female, when present, consists of several 

 bristles, while that of the male consists of a single strong, spine-like 

 organ . 



The frenulum-hook, which is present in the males of most moths, is a 

 membranous fold on the lower surface of the fore wing for receiving the 

 end of the frenulum, and thus more securely fastening the two wings 

 together (Fig. 329, / /?). As a rule, the frenulum hook arises from the 

 membrane of the wing near the base of cell C. 



