THE PBEDACEOUS DIVING BEETLES. 



207 



KEY TO SUBFAMILIES OF DYTISCIDiE. 



a. Episternum of metathorax not reaching the middle coxal cavity. (Fig, 



106. ) Subfamily I. Fkagmentati, p. 207 

 aa. Episternum of metathorax reaching the middle coxal cavity. (Fig 



107. ) Subfamily II. Complicate, p. 210 



In the accompanying cuts. Fig'. 106 rep- ^ 

 resents a diagram of a portion of the under A 

 surface of Laccophilus, which belongs to u^ ^)^^ 

 the subfamily Fragmentati, cc being the '^ f A 

 middle coxal cavity. It will be seen that * r ' 

 the mesosternal epimeron (ms. epm.) ar- ^ c>s. 



ticulates at its inner end with the meta- 

 sternum (rnt.). and thus cuts off the 

 metasternal episternum (mt. eps.) from 

 the coxal cavity. In Fig. 107. however, 



which is a diagram of similar parts of " a „„ Fig 106 ^ 6 _ Fig . 107. 

 Colymbites of the subfamily Complicati, (After Wickham - ) 



the mesosternal epimeron does not articulate with the metasternum, 

 and thus allows the episternum of the latter to reach the cavity. 

 These features are not, as a rule, difficult to make out, and form 

 the basis of the modern classification of the family, by Dr. Sharp. 



Subfamily I. FRAGMENTATI. 



The North American members of this subfamily are divided 

 among two tribes, both of which are represented in the Indiana 

 fauna. In all the species the scutellum is invisible. 



KEY TO TEIBES OF FRAGMENTATI. 



a. Hind coxse longer near the middle of the body; prosternum dilated be- 

 hind, truncate or nearly so. Tribe I. Noterini, p. 207. 

 aa. Hind coxa? longer near the sides of the body; prosternal process com- 

 pressed, reaching the metasternum. 



Tribe II. Laccophilini, p. 209 



Tribe I. NOTERINI. 



The members of this tribe are all small beetles having the body 

 convex, obtuse in front and pointed behind; front and middle 

 tarsi five-jointed; apex of front tibia 3 with a curved spur or hook. 

 Two genera occur in Indiana. 



KEY TO INDIANA GENERA OF NOTERINI. 



a. Last joint of maxillary palpus bifid or emarginate ; prosternal process 

 not broader than long ; hind tibiae less dilated ; length less than 3 mm. 



I. Canthydrus. 



[14—23402] 



