120 IIYDRADEPHAGA — DYTISCIDAE. 



a a. Elytra without distinct punctures, except 

 three tolerably regular rows. 



Oblong oval, slightly convex. Black, very shiny ; apical 

 light spot on elytra often indistinct ; legs pitch-black. 

 Upper-side with extremely feeble network, almost smooth. 

 Male with a tooth in middle of inner claw of anterior tarsi, 

 and swimming hairs beneath first joint only of posterior 

 tarsi. L. 4 1. Not very common. A. nitidus, Fab. 



h h. Elytra distinctly punctured, besides three . 

 irregular rows. 



Oblong oval, rather flat. Black, shiny; light spots on 

 elytra sometimes rather indistinct ; legs pitch-black, tibiae 

 and tarsi of front pairs reddish. Upper-side with close and 

 fine network ; side margins of thorax rather strongly 

 raised. Male with swimming hairs beneath first joint only 

 of posterior tarsi. L. 4 1 Common. A. guttatus,VQ.y\. 



JB -Z>. Anterior light spot on elytra constricted or 

 divided. 



Oblong-ovate, tolerably convex. Black, witli metallic 

 lustre, especially on elytra : reflexed margin of elytra red ; 

 front pairs of legs red, with a dark spot on femora and 

 intermediate tibiae, posterior legs pitchy, trochanters and 

 apex of femora reddish. Upper-side smooth, except the 

 irregular rows of punctures on elytra. Male with swim- 

 ming hairs beneath four joints of posterior tarsi. L. 3 j 1. 

 Common. A. didymus, 01. 



2. Thorax brown red. 



Ovate, convex. Brown-red ; smooth, spotless ; elytra 

 rather darker, with base and side margin a little paler; 

 sides of breast and abdomen black ; anterior pairs of legs 

 pitchy-red, posterior pair pitch-black ; antennae short, red- 

 dish. Male with swimming hairs beneath four johits of 

 posterior tarsi. L. 4 — 4J L Scarce. A. hrunneus, Fab. 



3. Thorax yeUow, with two black points. 



Oval. Head (except labrum, clypeus and frontal spots) 

 black ; elytra yellow, with irregular black spots, M'hich 

 leave base, suture, side margin and a small round spot 

 somewhat behind middle uncovered ; under-side Ijlack, 

 margins of abdominal segments somewhat widely reddish ; 

 legs yellow, posterior femora darker. Male with a tooth 



