230 



FAMILY 1\. DYTISC'ID.E. 



KEY TO INDIANA GENEKA OF DYTISCINI. 



«. Length one inch or more ; joints of hind tarsi not (ringed with flattened 

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

 of males with two large and numerous small disks. 



XIX. I>YTiscrs. 

 «(/. Length scarcel.v exceeding one-half inch; joints of hind tarsi fringed on 



the outer margin. 

 6. Spurs of hind tibite acute at apex ; claws of hind tarsi unequal. 



XX. Hydaticks. 

 1)1). Spurs of hind tilii:c emarginate at apex. 



c. El.vtra either 4-suIcate (female), or with distinct, clcisely phued. 

 moderate sized punctures (male). XXI. AciLirs. 



cc. lOlytra not distinctly punctured, sometimes ver.-\- finely punetulate 

 or partially aciculate. 

 (/. Jliddle femora with long conspicuous set;c. 



XXII. Thich.monectes. 

 (hi. Middle femora with short, stout sette. XXIII. Geaphoi)Kr:s. 



The emarginate or bifid tips of the tibial spurs in the last thi'ee 

 ueiiera are ver^■ fine, and must be looked for with a good lens. 



XTX. Dytiscus Linn. 1735. (Gr., "a diver.") 



To this genus lielong the largest of our diving beetles. They 

 are of a dark olive-brownish hue, with the elypeus and a .stripe 

 along the sides of thorax and elytra dull yellow ; front and hind 



margins o f thoi'ax 

 also usually more or 

 less yellow. (Fig. 

 115.) Form elon- 

 gate-oval, little con- 

 vex and of variable 

 width; elypens sepa- 

 rated from head by 

 a suture visible 

 across the full width 

 ef head ; thorax not 

 m a r g i n e d ; claws 

 e(|ua.l in both sexes. 

 The females of some 



Fi?. 115. Dytiscui:-a, lirv.i of D. murginalis devouring a larva of ^Pi'^^'lt'S always liaVC 



EpVaier.i; 6, pupv of .sime; r, D. fasdKnlris Say; grooved eljlron of ii i . ^ i -i 



femile; rf, front tarsus of male, under side, showing the suctioncups; r, 1^'''' elytra deeply antl 



H.ime of female. (After Riley.) ' , -, , 



broadly sub ate; i n 

 scmie they are always smooth, while in a third grcmp the females 

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

 species are known from Indiana, while three others perhaps occur. 



