184 The Orders of Insects 



asymmetrically to the left side within the beak. The 

 prothorax is large and free, the other two segments 

 of the fore-body partially fused together. The legs 

 are short, and the feet have only one or two segments 

 which bear two minute claws and a prominent bladder- 

 like sucker. The wings of the two pairs are long, 

 narrow, membranous, with very few nervures, and 

 fringed with long hairs •, the forewings are some- 

 what longer than the hindwlngs, and rather firmer 

 in texture ; in several genera wings are wanting. 

 Ten abdominal segments are present, the last of 

 which is often tubular (fig. loo) (116). 



Life-history and Habits. — The young nymphs 

 when hatched are closely like the adult in form, 

 but soft-skinned and of course without wings. In 

 the stage before the final change the nymph is 

 sluggish, its limbs obscured by a film, and the wing- 

 rudiments enclosed in sheaths : in some cases it is 

 said to be immovable and to take no food. The 

 development of the Thysanoptera therefore exhibits 

 an interesting transition towards a true metamor- 

 phosis. The insects live, often in great numbers, on 

 the leaves and flowers of plants whence they suck 

 the sap; also under bark. They are probably of 

 general distribution, but have hardly been studied 

 beyond the limits of Europe and North America. 

 The order is divided into three families. Less than 

 200 species are known (116). 



^olothripidae.- — The JEolothripida have nine-segmented feelers ; 

 the forewings have a costal nervure around the whole margin, and 

 two longitudinal nervures. In the female an ovipositor is de- 

 veloped from four processes on the eighth and ninth abdominal 

 segments ; this organ when extended is curved backwards. 



Thripidae. — The Thripida agree with the preceding family in 

 wing-neuration and in the presence of an ovipositor in the female ; 

 but this organ is curved downwards instead of backwards, and the 

 feelers have only eight segments. 



Phlceothripidae. — The Fhlceothrifida are distinguished by the 



