CHAPTER XV 



THE WINGS OF THE THYSANOPTERA 



The winged members of this order have four wings; these are similar in 

 form, long, narrow, membranous, not plaited, with but few or with no veins, 

 and only rarely with cross- veins ; they are fringed with long hairs, and in 

 some species are armed with spines along the veins or along the lines from 

 which veins have disappeared. 



The two wings of each side are united by spines, the arrangement of 

 which are described by Hinds ('03) as follows : "Upon the costa of the hind 

 wing, near its base, stand about five short spines in the Terebrantia and two 

 or three in Tubulifera, which are hooked at their tips. When the wings 

 are spread in flight these tiny hooks engage a membranous fold on the 

 underside of the scale [anal area] of the fore wing. Beyond these small 



Fig. 265. — Fore wing of JElothrips nasttirtii (After Jones). 

 The lettering is original. 



hooks stand a single stouter spine which also forms a hook. From the hind 

 angle of the scale of the fore wing proceed two long, stout spines, standing so 

 closely together as to often appear like one, and these engage the solitary 

 stouter hook on the hind wing. Thus united the wings move together, but 

 as the connection is so near the bases of the wings it can not be very strong. ' ' 

 When at rest the wings are folded back flat upon the abdomen. Although 

 the wings are usually present in adults, certain species are apterous. 



Even in the most generalized forms the venation of the wings is greatly 

 reduced. A fore wing of ^olothrips nasturtii, one of the more generalized 

 members of the order, will serve as an illustration of this fact (Fig. 265). 

 This figure is a copy of one given by Jones ('12), to which I have added 

 letters indicating my conclusions regarding the homologies of the wing- 

 veins. 



The costal vein is present and is continued by an ambient vein, which 

 margins the entire preanal area of the wing (Fig. 265, avi). The ambient 



(207) 



