CHAPTER XXI 

 THE THYSANOPTERA 



The Thysanoptera — sometimes called Physapoda — are very small 

 insects, peculiar in many ways. The common name for members of 

 this group is Thrips, unchanged in spelHng whether one or many are 

 referred to. 



As a whole these insects appear to have some affinities with the hemip- 

 teroid groups (Anoplura, Hemiptera and Homoptera) yet to be consid- 

 ered, but are generally looked upon as forming an order by themselves, 

 though in some regards they seem to have certain relations to the Cor- 

 rodentia and Mallophaga. It is not improbable that they form a group 

 originating not far from the common trunk of all 

 the above-named orders. 



Thrips vary from one-fiftieth to one-third 

 of an inch or more in length. Their mouth 

 parts (Fig. 148) form in part a short, stout cone 

 attd,ched far back on the underside of the head, 

 composed of the labrum, a portion of the maxillae, 

 and the labium. Within this cone are three 

 bristles consisting of the lobes of the maxillae and 

 one mandible, the other not being developed. 

 The animals are sucking insects. Four wings p^^ i48.— Side view of 

 are usually present, rather long and narrow, with the head and prothorax of 



, p . 1 1 1 • 1 1 11 • a Thrips to show the mouth 



few vems, and frmged behmd and generally m ^^^^^ ^p^^^ ^ s. D. A. 

 front also, with slender hairs, longer than the Bur. Ent. Bull. 68 Part 2.) 

 breadth of the wing itself. When at rest the 



wings lie flat on the top of the abdomen. In some cases they are greatly 

 reduced in size or may even be wanting entirely. The tarsi are com- 

 posed either of one or two segments, usually the latter: at the tip is a 

 bladder-like portion which can be drawn into the segment or pushed 

 out. The abdomen consists of ten segments, the last either conical or 

 tubular in form. 



Summarizing these facts, the adult Thysanoptera may be described as: 

 Small insects with greatly modified mouth parts forming a cone attached 

 to the hack part of the head beneath and used for sucking. Wings four, 

 generally present, long, narrow, with few veins, and fringed behind {usually 

 in front also) with long hairs. Tarsi of one or two segments, the tip with a 

 bladder-like swelling capable of being drawn into the tarsus. Abdomen of 

 ten segments, the last either conical or tubular. Metamorphosis incomplete 

 but approaching completeness. 



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