124 IIYDKADEPHAGA — GYIUNIDAE. 



Hydati'ciis. 



A. lutermediate tarsi of male not much dilated, their first 



three joints with two rows of sucker-cups beneath. 



Oval. Yellow, vertex of head, two frontal spots and 



two broad bands (including the anterior and posterior 



margins) on thorax black ; elytra sprinkled with dark 



brown spots. L. 6| 1. Scarce. H. cinereics, Lin. 



H. Intermediate tarsi of male considerably dilated, with 



four rows of sucker-cups beneath. 



a. Elytra black, with a broad side border (interrupted 

 by black lines) and a narrow transverse band behind 

 base yellow. 



Oblong oval. Head black, front and a pair of frontal 

 spots rust-red ; thorax yellow, with a broad triangular 

 black spot at base ; under-side pitchy. L. 5|^ 1. Rather 

 common. ff. transversalis, Berg. 



b. Elytra black, with a broad yellow side border, some- 

 times sprinkled with black lines behind. 



Oblong-ovate. Head and thoi-ax black, mouth and two 

 frontal spots, anterior margin and sides of latter rust- 

 yeUow ; under-side black. L. 6 1. Not uncommon. 



H. seminigcr, De G. 



GYMIJSriDAli:, 



A. Last abdominal segment rather flat, rounded at apex, 

 little or not at all fringed ; elytra with rows of punctures. 



Last joint of labial palpi as long as the two preceding 

 joints together ; mentum without any middle tooth ; outer 

 lobe of maxillae narrow, thin and inarticulate, lying close 

 against the inner lobe. Gyrinus, Lin. 



li. Last abdominal segment ])romJnent, conical, fringed 



with hairs at the apex ; elytra irregularly punctured. 



Last joint of labial palpi as long as the three preceding 

 joints together ; mentum with a small middle tooth ; outer 

 lobe of maxillae wanting. Orectochilus, Esclisch. 



Gyrinus. 



uL, Undur-sidc entirely rust-red. 



