THRIPS 



(Order Physopoda.) 



The very minute insects known as "thrips" belong to this 

 order, which is a very well differentiated group and has apparently 

 no very close relatives among the insects. It is unfortunate that 

 in this country the name thrips has been applied largely by vine- 

 growers to some of the little leaf-hoppers of the family Jassidae 

 (q. v.), but the name was long preoccupied, both popularly and 

 scientifically, by the physopod insects, which, by the way, are 



also sometimes called Thysanoptera. 

 They are very minute, slender in- 

 sects, with four wings which are 

 also very slender and very short, 

 perfectly transparent and practically 

 without veins. They are fringed, 

 however, with long delicate hairs 

 and lie along the back of the abdo- 

 men when at rest. The metamor- 

 phosis is incomplete and the mouth- 

 parts are of very curious shape, but 

 probably function in sucking. They 

 are really intermediate between true 

 biting and true sucking mouth- 

 parts. A striking peculiarity of the mouth-parts is that they fre- 

 quently differ on the two sides. In other words, they are 

 asymmetrical. Although the metamorphosis is incomplete, what 

 may be called the pupa is not active. The larvae, however, are 

 not in the least worm-like and resemble the adults, except for 

 the lack of wings. The feet are curiously constructed and have 

 a little bladder-like vesicle at the tip, from which fact the name 

 of the order was derived. 



The thrips are found in the greatest numbers in the flowers 

 of flowering plants and there can be little doubt that they do 



318 



Fig. 213. — Thrips tritici. 



