Both species agree in their predaceous habits, omnivorous diet and great fecundity.
As is the case with other water-bugs, this insect is predaceous and feeds upon aquatic grubs or worms. The body is richly supplied with long hairs, which serve to entangle bubbles of air for purposes of respiration.
If it is a risky matter to plant out the robust young fry of trout under an age of three months, it would seem to be an infinitely more speculative proceeding to plant out the delicate week-old larvae of sea-fishes in an environment which teems with predaceous enemies.
Although occasionally seen abroad during the day, especially in wild and desolate regions, where it is subject to little molestation, the night is, as in the case of so many other predaceous animals, the period of its greatest activity.
A family of predaceous bugs that attack other insects and suck their juices; the beak is short, and carried under the head in a hooklike curve, not - as in the preceding families - lying close against the breast.
The term mimicry has also been applied to resemblances of a different kind from the two enumerated above - resemblances, that is to say, by which predaceous species are supposed to be enabled to approach or mix without detection with animals they prey upon or victimize in other ways.
Various species among those that are predaceous attack smaller insects, hunt in packs crustaceans larger than themselves, insert their narrow heads into snail-shells to pick out and devour the occupants, or pursue slugs and earthworms underground.
This may be associated with mud-eating habits; but it is not wholly certain that this is the case; for in Chaetogaster and Agriodrilus, which are predaceous worms, there is no protrusible pharynx, though in the latter the oesophagus is thickened through its extent with muscular fibres.
Several families of bugs are predaceous in habit, attacking other insects - often members of their own order - and sucking their juices.
It is preyed upon by the larger predaceous fishes of fresh waters, and owing to its silvery appearance is a favourite bait in pikefishing.