B 



266 FAMILY VI. HYDROPHILID^. 



elytra usually striate; mesosternum elevated between and in front 

 of the middle coxa'. About 25 species are known from the United 

 States, many of them lieing common to this country and Europe. 

 Of these Dr. Horn states that "but a small number owe their pres- 

 ence in our fauna to introduction by human agency. They appear 

 to be rather members of a eircumpolar fauna, equally native in 



either hemisphere, and dis- 

 tributed at a time when con- 

 tinental division was less ab- 

 r u p t than at present. ' ' 

 Eleven species have been 

 Fig. 130. Fig. 131. taken in Indiana and several 



.4 , middle coxal cavity. W, metasternal area. (After Horn.) ,i n n j.i 



others doubtless occur. 



KEY TO INDIANA SPECIE.S OF CEKCYON. 



a. Intervals of elytra alternately higher or subcostiform at ape.x, the stria? 

 deep ; surface sparsely piibescent : color pale reddish-brown. 



518. PUBESCENS. 



aa. Intervals flat or slightly convex : surface smooth. 



J). Metasternal area extended on each side by an oblique line. (Fig. 

 130.) 

 c. Thorax without basal marginal line, its surface wholly black. 



d. Elytra piceous. with pale apex; surface distinctly punctulate; 



palpi and autennse piceous. 519. h.^morriioidalis. 



dil. Elytra reddish, with a large scutellar triangle and humeral stripe 



piceous. 



e. Elytra very distinctly punctulate ; epipleura piceous ; palpi pale. 



520. melanocepiialus. 



ee. Elytra indistinctly punctulate ; epipleura pale ; last joint of 



palpi piceous. 521. pygm.^us. 



cc. Thorax with distinct basal marginal line, paler at sides; elytra 



pale with transverse piceous band behind the middle; palpi pale. 



522. nigriceps. 

 66. Metasternal area median only. (Fig. 131.) 



f. Side marginal lines of thorax extending for a short distance along 

 the basal margin ; elytra dull reddish-yellow with a large oval 

 piceous spot on suture behind middle Avhich extends narrowly to 



apex. UNIPUNCTATUS. 



ff. Side marginal lines reaching the hind angles only. 



g. Interval between the seventh and eighth striae normally wide, 

 with at least two rows of punctures. 

 h. Form oval, never very convex ; head oblique. 



/. Elytra piceous black, with a sharply limited yellowish apical 

 space extending along the sides toward the base. 



523. PEiETEXTATUS. 



I 



