22O Bugs, Cicadas, Aphids, and Scale-insects 



ant 



present), which, when the insect is at rest, are laid back along the abdomen 

 unfolded, and parallel or slightly overlapping at the tips. Only about forty 

 species are yet known in this country, but as practically only one entomol- 

 ogist has attempted to make a systematic study of the group and his speci- 

 mens were mostly collected in a single locality (Amherst, Massachusetts), 

 it is certain that many species are yet to be found and named. This 

 entomologist, Hinds, has published in a recent paper (Contrib. to a Mon- 

 ograph of the Thysanoptera of N. A., Proc. U. S. Nat. Mus., vol. xxvi, 

 1902) practically all that is known of our American species, and I have 

 largely drawn on his paper for the present short account. 



Although the thrips used to be classified as a family of the order Hemip- 

 tera, they are now, and rightly, assigned to an order of their own, called 

 Thysanoptera (fringe- wings). This separation is due tc the peculiar charac- 

 ters of their mouth -parts and of the feet, and 

 to the interesting character of their develop- 

 ment, which is apparently of a sort of tran- 

 sitional condition between incomplete and 

 complete metamorphosis. The food of the 

 thrips is either the sap of living plants or 

 moist, decaying vegetable matter, especially 

 wood and fungi. The mouth-structure in ac- 

 cordance with this food habit is of a sucking 

 type, with mandibles and maxillae modified to 

 be needle-like to pierce the plant epidermis. 

 But the mouth-parts are curiously asym- 

 metrical, the right mandible being wholly 

 wanting and the upper lip being more ex- 

 panded on one side than the other (Fig. 308). 

 The peculiarity in the life-history consists in 

 a quiescent, non-food-taking stage like the 

 pupal stage in insects of complete metamor- 

 phosis, but before reaching this stage well- 

 developed external wing-pads have appeared, 

 just as happens in the case of immature 

 insects of incomplete metamorphosis. Finally, 

 the peculiar character of the feet is due to the 

 presence of a small protrusile or expansile 

 membranous sac or bladder at the tip of the 

 tarsus, instead of claws or fixed pads, which seems to play a not well 

 understood function in the holding on by the insect to the leaf or 

 flower parts which it may have occasion to visit. The bladder seems 



FIG. 308. Head and mouth- 

 parts, much enlarged, of 

 thrips. ant., antenna; lb., 

 labrum; md., mandible; mx., 

 maxilla; mx.p., maxillary pal- 

 pus; li.p., labial palpus; m.s., 

 mouth-stylet. (After Uzel; 

 much enlarged.) 



