NO. 1310. NORTH AMERICAN TIIYSANOPTERA-HINDS. 101 



above, it is seen that the bases of the claws are strong!}- broadened 

 within and somewhat less so without, and that the inner prolongations 

 touch and are flexibly joinetl together. Both claws are supported upon 

 the bracket-like ring at the base of the cup, while the folded mem- 

 branous wall reaches beyond the claws. The chitinous rod unites near 

 the support with the two tendons coming from the outer projections 

 of the claws. \Mien the bladder is brought into an active condition, 

 the claws bend out from each other and the folded portion Ijetween 

 them spreads out, while the distal portion, unseen in the inactive foot, 

 becomes pushed out as the bladder. By a proximal pull upon the 

 chitinous rod the tendons are drawn back and the claws thereby are 

 spread out, moving around the bracket-like support with which they 

 are connected as on a pivot. As the claws are grown together with 

 the folded lobe, the lobe must be unfolded, but this does not explain 

 how the membranous lobe can be protruded as a swollen bladder. If 

 a swollen bladder be pricked or ruptured the blood pours out and the 

 bladder collapses quickly. We must therefore conclude that ])lood 

 pressure, acting with the mechanism just described, is largely instru- 

 mental in the protrusion of the bladders. 



Other' organs of douUful funetion.—ln the basal segment of the 

 tarsus or the extremity of the tibia there has been found in a few 

 European species a small, pear-shaped organ which has been consid- 

 ered as a gland, and some have thought this the structure which pro- 

 duced the swelling of the bladders, but as this supposed gland is much 

 smaller than the bladder which it is supposed to fill, this can not be, 

 and its function remains still problematical. 



Near the line of union of the femur with the trochanter, Tryboni 

 has found in certain Phceothripidte an organ or a group of organs 

 which suggest to him the auditory organ on the base of the til)ia in 

 some Locustidfe. Trybom speaks of 'this structure as an elongated, 

 thinly chitinizod area, almost transparent. The areas are found on the 

 side of the base of each femur near the line of its union with the 

 trochanter. They are variable in shape and may ])e different on the 

 opposite legs of the same pair. In each light area is a row of round 

 structures having a dark point in the center of each. 



These peculiar structures are . small and easily overlooked, but 

 Trybom has seen them in many species of Terebrantia as well as 

 Tubulifera, and the writer has seen them in every species in his own 

 collection. It appears, therefore, that they are afways present, but as 

 to their function we can only guess. 



The wings of Thysanoptera are no less characteristic than are their 

 feet. To be sure each character shown by them may be found in the 

 wings of some other group of insects; nevertheless the combination of 

 characters found here is unifjue. They are long, slender, meml)i-anous, 



