162 Illinois State Laboratory of Natural History. 



commonly taken in water pertain to the Haliplidce, Dytiscida?, 

 Gryrinidae, and Hydrophilidai. Several other families may ap- 

 propriately be considered in connection with aquatic insects 

 because of their constant abundance in the moist earth along 

 water and on sub-aquatic vegetation. These beetles are un- 

 questionably an important source of food to the carnivorous 

 aquatic animals, and themselves doubtless attack and devour 

 their aquatic neighbors when chance brings these latter ashore. 



Family Carabid.^, (Predaceous Ground Beetles.) 



A few species of Bembidium and Elaphrus were gener- 

 ally to be found on sunny days at the edges of sloughs, running 

 over the mud. Under the logs in the neighborhood were the 

 usual carabids of such situations — Galerita, Chlsenius, and 

 Pterostichus — but they were by no means common. The 

 seining operations sometimes revealed the presence of certain 

 burrowing species, such as Oinophron americanmn, in the moist 

 mud of the shores ; and in the latter part of A.ugust a sudden 

 rise in the water surprised numerous examples of Clivina and 

 Bembidium, which were noted floating on the surface at the 

 mercy of predaceous aquatic animals. 



Family Haliplid^. 



The larva} of this family are odd-looking creatures with 

 strong spines or long-jointed respiratory appendages on the 

 segments, the 9th (last) segment being produced and divided. 

 Tarsi with a single claw. The larv.i? of our two genera may 

 be recognized by the following characters : 



Haliplus. — Spiracles present, no branchial filaments. Max- 

 illary palpi three-jointed. Clypeus truncate. 



Cnemidotus. — No spiracles, branchial Hlaments long and 

 jointed. Maxillary palpi two-jointed. Clypeus notched. 



Cnemidotus 12-punctatus, Say. 



{Haliplus 12-pHnctafiis, Say, Trans. Am. Philos. Soc, N. 

 Ser., ii, 106, 1825.) 



The beetles were moderately common in Willow Slough, 

 where they were brought out by the dredge and dip net. 

 Females taken August 15 contained ova with advanced em- 

 l)ryos. 



