94: 



The families containing aquatic species are Amphizoidai, Halip- 

 liclte, Dytiscidte, Gyrinidae, Hydropbilidae, Parnida^ and Dascyl- 

 lidfB. The great majority of individuals and species commonly 

 taken in water pertain to the Haliplid*, Dytiscidse, Gj^riuid*, 

 and Hydrophilidoe. Several other families may appropriately 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 unquestionably an important 

 source of food to the carnivorous laquatic 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 generally to 

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

 mud. Under the logs in the neighborhood were the u.sual cara- 

 bids of such situations — Galerita, Chlaenius, and Pterostichus — but 

 they were by no means common. The seining operations some- 

 times revealed the presence of certain burrowing species such as 

 Omophron americanum, in the moist mud of the shores; and in 

 the latter part of August 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 ani- 

 mals. 



Family Haliplid^. 



These are small water beetles less than a quarter of an inch 

 long, and commonly to be distinguished at sight from members of 

 the following three families by the slender legs, which are not 

 suited to rapid locomotion in the water, and by the projecting 

 head,-— the latter being in most other aquatic beetles, widened, and 

 immersed in the thorax. The antenntB are made up of ten seg- 

 ments, and are inserted in the front. The larvjt are odd-looking 

 creatures with strong spines or long-jointed respiratory append- 

 ages on the segments, the 9th (last) segment being produced and 

 divided. Tarsi with a single claw. The larv;v of our two genera 

 may be recognized by the following characters: 



Haliplus. — Spiracles present, no branchial filaments. Maxillary 

 palpi three-jointed. Olypeus truncate. 



Cnemidotus. — No spiracles, branchial filaments long and jointed. 

 Maxillary palpi two-jointed. Clypeus notched. 



Cnemidotus 12-punctatus, Say. 



(Haliplus 12-punctatus, Say. Trans. Am. Philos. Soc, N. Ser.. ii, 

 106, 1825.) 



The beetles were moderately commom in Willow Slough, where 

 they w^ere brought out by the dredge and dip net. Females taken 

 August 15 contained ova with advanced embryos. 



