982 FAMILY XXXI. — GERRID^E. 



bolan genus Sminthurides and it would be interesting to know if they are 

 used in the same manner as in Sminthurides, the male of which winds 

 them around the antennae of the female during copulation. They seem 

 at least admirably adapted to this purpose. Another point of interest 

 is that some of the spines and chitinous processes of the male antennae 

 and legs seem to be composed of hairs cemented together by some viscous 

 fluid. These insects probably have some glands secreting such a fluid. 

 Under the microscope the last antennal joint shows several sense-organs 

 and at the very tip an excavation bearing a short brush. A brush is 

 also situated at the inner end of the fore tibiae. The spongy pit at the 

 apical part of the third antennal joint may also be a sense-organ or pos- 

 sibly a suctorial organ. Unfortunately little is known of the biology of 

 these insects. As they thrive only on running water it would be difficult 

 if not impossible to rear and study them in aquaria." 



KEY TO EASTERN' SPECIES OF RHEUMATOBATES. 



a. Mesosternum wholly yellow; mesonotum distinctly broader than long 

 in both sexes ; hind femora of males swollen, strongly curved and 

 fringed within at basal third with a tuft of long hairs. 



b. Median yellow spot on mesonotum large, not or scarcely narrower 



than that on pronotum; tooth or spine of fourth antennal of male 

 placed in front of middle. 1120. rileyi. 



bb. Median yellow spot of mesonotum much smaller, distinctly narrower 

 than the one on pronotum, in female sometimes wholly wanting; 

 spine on fourth antennal of male placed behind the middle. 



1120a. var. palosi. 

 aa. Mesosternum yellow with the front margin and two feebly divergent 

 stripes brownish-black; mesonotum scarcely, male, or but slightly, 

 female, broader than long, its median pale spot narrower than that 

 of pronotum; hind femora of male, if swollen and curved, with 

 very short fine hairs along the whole inner margin. 



c. Hind legs in both sexes simple, straight and hairless; middle tibiae 



of male fringed with short hooked hairs along the entire inner 

 side. 1121. tenuipes. 



cc. Hind femora of male swollen and curved as in rileyi; middle tibiae 

 of male fringed with long straight hairs on inner side of basal 

 half, with short straight ones on apical half. 1122. trulliger. 



1120 (1297). Rheumatobates rileyi Bergroth, 1892a, 321. 



Oblong, robust, narrowed behind. Above velvety black; a transverse 

 median spot on pronotum, a diamond-shaped median one on mesonotum, 

 a rounded one above the middle coxae, the front femora and the reflexed 

 connexivum, yellow; antennae, beak and middle and hind legs fuscous- 

 brown, the bases of first antennals and of the femora yellow; under 

 surface pale yellow, the abdomen often with a dusky tinge. Male with 

 first joint of antennae gradually thickened from the base, armed beneath 

 at apical third with one or two short spines; second joint very short, 

 armed with a slender spine near base; third strongly curved and with a 

 shallow spinose fossa at apical thii-d; fourth with apical half curved, 

 acute, armed in front of middle with a strong tooth. Middle tibiae of 



