Insect guide > Bugs > Giant Water Bugs

Giant Water Bugs


(Family Belostomatidae.)
The remarkable insects of this family have long attracted attention. They include the largest of living bugs, are strictly aquatic in their early stages and are predatory in habits, living at the bottom of ponds and feeding upon other aquatic animals in­cluding fish. Their fore legs are fitted for grasping their prey and their hind legs for swimming. When full grown, however, their wings are developed and they fly strongly and for great distances.

They have been found in the midst of great cities far from ponds and are attracted to electric lights on the tops of high buildings. So attractive are electric lights to these great bugs that they congregate about them in extraordinary numbers and thousands of them which have fallen to the ground beneath such lights are crushed beneath the feet of passers by. They have in fact become generally known as "electric light bugs". While such hosts of them are destroyed in this way, their numbers do not seem to be reduced, but it is bad policy to have electric lights near fish breeding establishments or artificial fish ponds.

The two most abundant and the largest of our native species are Belostoma americanum Leidy and Benacus griseus Say. Both are very large, flat, grayish or brownish bugs and were long confused. The Belostoma has a double groove on the underside of its fore thighs which is lacking on the thighs of the Benacus. The eggs are large and spherical and are attached to the stems of water plants or to some other convenient object. Of Benacus griseus Uhler says: "It is the facile master of the ponds and estuaries of the tidal creeks and rivers of the Atlantic States. Developing in the quiet pools, secreting itself beneath stones or rubbish, it watches the approach of a Pomotis, mud-minnow, frog or other small-sized tenant of the water, when it darts with sudden rapidity upon its unprepared victim, grasps the creature with its strong, clasping fore legs, plunges its deadly beak deep into the flesh, and proceeds with the utmost coolness to leisurely suck its blood. A copious supply of saliva is poured into the wound, and no doubt aids in producing the paralysis which so speedily follows its puncture in small creatures."

The genus Zaitha contains similar water bugs of smaller size which have frequently been mentioned and figured from the curious habit of carrying the eggs plastered in a group on the back of the adult insect. For a long time it was supposed that the female sticks her eggs to her own back and the case was supposed to parallel,in a way, that of the famous Surinam toad.

A German observer, Schmidt, however, found that many males carried eggs, but the method and purpose of attachment remained a mystery until it was cleared up by aquarium observations made by an American, Miss Slater, who found that the female, vis et armis, customarily lays them on the back of the unwilling male. Sometimes she has to struggle for hours to accomplish her fell purpose, but she does accomplish it in the end and her spouse is converted into an animated baby carriage. Says Miss Slater: "That the male chafes under the burden is unmistakable; in fact my suspicions as to the sex of the egg-carrier were first aroused by watching one in an aquarium which was trying to free itself from its load of eggs, an exhibition of a lack of maternal interest not to be expected in a female carrying her own eggs. Generally the Zaithas are very active, darting about with great rapidity; but an egg bearer remains quietly clinging to a leaf with the end of the abdomen just out of the water. If attacked, he meekly received the blows, seemingly preferring death, which in several cases was the result, to the indignity of carrying and caring for the eggs".

The full life history of none of these giant water bugs has been properly described in the U.S. The young Belostomas are said to have two tarsal claws instead of one as when adult, but their growth has not been followed. About fifty species of the family are known, of which about one-half inhabit the United States.