THE PREDACEOUS DIVING BEETLES. 



231 



KEY TO INDIANA SPECIES OF DYTISCUS. 



a. Labrum distinctly emarginate at middle. 



h. Hind coxal processes rounded or acute, not spinose. 



c. Thorax with sides yellow, base and apex not or only indistinctly so. 

 d. Abdominal segments reddish-brown with a piceous hind margin ; 

 elytra of female always sulcate. 449. fasciventkis. 



(hi. Abdominal segments uniform black or piceous; elytra of females 

 smooth. 



e. Elytra without a narrow subapical cross-bar of yellow; smaller, 

 25-27 mm. 450. iiybridus. 



ee. Elytra with a narrow oblique subapical cross-bar; larger, 32- 

 35 mm. 451. verticalis. 



cc. Thorax with base and apex, as well as sides, distinctly and rather 

 broadly yellow ; females dimorphic. 

 /. Hind coxal processes acute ; length 33 mm. marginalis. 

 ff. Hind coxal processes obtuse; length 30 mm. sublimbatus. 

 l)l>. Hind coxal processes produced, distinctly spinose; thorax with base, 

 apex and sides broadly yellow ; length 31-35 mm. dauricus. 

 aa. Labrum nearly truncate at middle; thorax with all the margins dis- 

 tinctly and broadly yellow ; females dimorphic. 452. harrisii. 



449 (1481). Dytiscus fasciyentris Say. Long's Exped.. II, 



270; ibid. I, 177. 

 Elongate-oval. Greenish-black above; thorax margined 

 with yellow only on the sides, or with a faint trace of yel- 

 low at base and apex. Elytra of female each with ten 

 grooves which reach beyond the middle; their apical third 

 finely and rather densely punctate. Length 25-28 mm. (Fig. 

 116.) 



Dekalb and Marion counties; frequent. April 10- 

 July 18. 



450 (1782). Dytiscus hybridits Aube, Spec. Gen., VI, 1838, 116. 

 Regularly ovate. Thorax shorter than in fasciventris, the apex usually 



narrowly yellow and sometimes with a faint yellow line at base. Pale mar- 

 gin of elytra of nearly equal width throughout. Length 2G-2S mm. 



Lake. Laporte. Starke. Vigo and Posey counties; frequent. 

 April 15-September 19. 



451 (1483). Dytiscus verticalis Say, Trans. Amer. Phil. Soc. II. 1S23, 



92; ibid. II, 500. 



Oval, rather broad. Thorax margined with yellow only on sides. Ely- 

 tra with three rows of well marked dorsal punctures ; the marginal yellow 

 line narrowing on apical half, the subapical line often somewhat indistinct. 

 Length 33-35 nun. 



Beach of Lake Michigan near Millers. Lake Conntv; scarce. 

 May 28. 



_ Fig. 116. 



Xatural size. 



