342 AN INTRODUCTION TO ENTOMOLOGY 



and the Homoptera, which are described in detail in later chapters. 

 The three thoracic segments are well developed. The wings are 

 laid horizontally on the back when not in use; they are very narrow, 

 but are fringed with long hairs (Fig. 391), which, diverging in flight, 

 compensate for the smallness of the membrane. The fringing of the 

 wings suggested the name Thysanoptera, by which the order is known. 

 The two longitudinal veins that traverse the disk of the wing in 



ant 



Fig. 391. — Fore wing of ^lothrips nasturlii. (After Jones.) The lettering is original. 



the more generalized forms I believe to be the radius and the media 

 respectively. The costal vein is continued by an ambient vein, which 

 margins the entire preanal area of the wing (Fig. 391, am). The 

 ambient vein is termed the "ring vein" by writers on this order, al- 

 though the term ambient vein has been long in use for veins in this 

 position. There is a short longitudinal vein separating the anal and 

 preanal areas; this is doubtless the anal vein (Fig. 391, yl). An organ 

 for uniting the two wings of each side, and consisting of hooked spines 

 situated near the base of the wings and a membranous fold on the under 

 side of the anal area of the fore wing, is described byHinds ('02). 



In some species one or both sexes are wingless in the adult state; 

 and in others, short -winged forms occur. 



The legs are well developed, but are furnished with very peculiar 

 tarsi. These are usually composed of two segments; the last seg- 

 ment terminates in a cup-shaped or hoof-like end and is usually 

 without claws. Fitted into the cup-shaped end of the tarsus there is 

 a very delicate, protrusile, membranous lobe or bladder, which is 

 withdrawn into the cup when not in use but is protruded when the 

 tarsus is brought into contact with an object. This is one of the 

 most distinctively characteristic features of the members of this order. 

 It was this feature that suggested the name Physopoda which is ap- 

 plied to this order by some writers.* 



The abdomen consists of ten distinct segments. The form of the 

 caudal segments differs in the two suborders as indicated below. 



The manner of oviposition differs in the two suborders. In the 

 Terebrantia the female cuts slits with her saw-like ovipositor and 

 deposits her eggs singly in the tissue of the infested plant. In the 

 Tubulifera it is evident that the eggs must be deposited on the surface. 



*Physopoda: physao {<pv(rdo}), to blow up; pous (toi;s), a foot. 



