230 



FA.Ml LY I^". DYTISOID.-E. 



KEY TO INDIANA GEMEliA OF DYTISCINI. 



a. Leugtli one inch or more; joints of hinfl tarsi not fringed \Yith flattened 

 hairs on the outer margin, the last one with two claws; front tarsi 

 of males with two large and nunierdns small disks. 



XIX. Dytiscus, 

 ita. Length scarcely exceeding one-half incJi ; joints of jiind tarsi fringed on 



the outer margin. 

 h. Spurs of hind tib!;e acute at apex; claws of hind tarsi uneciual. 



XX. Hydaticis. 

 ?>6. Spurs of hind tibia' emarginate at apex. 



c. Elytra either 4-sulcate (female), or with distinct, closely placed, 

 moderate sized [lunctures (male). XXI. Acilixs. 



cc. Elytra not distinctly punctured, sometimes very finely punctulate 

 or partially aciculate. 

 d. Middle femora witli long conspicuous seta\ 



XXII. Thermonectes. 

 (Id. Middle femora with short, stout set;e. XXIII. Gkaphoder!: s. 



Tlie emarginate or l)ifi»l ti])s of tlic tibial spurs i'l tlie last thi'cc 

 genera are ver^- fine, and lunsf l)e looked for with a nood lens. 



XTX. Dytiscis Linn. M'-\'). (Or., "a diyer.") 



To this genus belong the largest of oui- diving beetles. They 

 are of a dark olivedjravvnisli line, with the elypeiis and a stripe 

 along the sides of thorax and elyli'a dull yellow; front and hind 



margins o f thorax 

 also usually more or 

 less yellow. (Fig. 

 115.) Form elon- 

 gate-oval, little con- 

 vex and of variable 

 width ; clypeus sepa- 

 rated from head by 

 a suttire visible 

 across the full width 

 of head; thorax not 

 m a r g i n e d ; claws 

 (Mpial in both sexes. 

 The females of some 



Fis. 115. Dytiscu5:-«,, Lirva of h. m-,r.;'»'/i.s- dovouring a larva of ■'^Pe<'lf^S ahvaVS liave 



Ephemera; 6, piipi of .same; c, I), inxnr, ,ilnx S:iy; grdjved elytron of ^u ,J,-(-,,n rlor^rdAr nnrl 



fpinile; f/, front tarsus of male, under side, -Imwing the .suction cups; c '^'" ' '.* ' ' '' tl( A piy ailLl 



.s.uiie of female, (.\fter Riley.) i 1 1 i , 



hrcadiv snlcate ; i n 

 .some they are always smootli, while in a third gi-oup the females 

 are dimorphic, i. e., have either smooth or sulcate elytra. Four 

 species arc known from Indiana, while three othei's perhaps occur. 



