William F. Lyon
|Common Name||Scientific Name|
|Dobsonfly||Corydalus cornutus (L.)|
|Water Boatman||Sigara atropodonta (Hungerford)|
|Backswimmer||Notonecta undulata (Say)|
|Giant Water Bug||Lethocerus americanus (Leidy)|
|Water Strider||Gerris remigis (Say)|
|Water Scavenger Beetle||Hydrophilus triangularis (Say)|
|Whirligig Beetle||Dineutus americanus (Say)|
|Predaceous Diving Beetle||Dytiscus verticalis (Say)|
Several kinds of aquatic insects may become a nuisance by their presence in homes, backyards and swimming pools. Many are attracted to lights and may accidentally enter structures or fall into swimming pools, while others may actually live in neglected pools. They do not cause harm to humans, pets, domestic animals, structures, possessions or crops. They will not reproduce or establish themselves indoors. Some such as the dobsonfly, backswimmer and giant water bug can inflict a painful bite if handled carelessly.
Adults are quite large, measuring two to four inches from the front of the head to the wing tips. They are soft-bodied, brownish body (faintly marked with brown of a different shade), with many cross veins and a white dot in each cell of the wings. The wings are held rooflike over the body. Males have long, sickle-shaped mandibles (jaws) about half as long as the body, while females have short inconspicuous jaws. They are attracted to lights, have a fluttery flight and are usually found near or some distance from a body of water. Adults are not active during the day, live briefly and are not believed to feed. Larvae, known as "hellgrammites," are aquatic, occurring under stones in fast-flowing shallow water (streams), and make excellent fish bait. Larvae can swim, but usually crawl, live three years before adulthood, grow up to two to three inches, feed on small aquatic organisms and can inflict a painful bite when mishandled.
Adults are soft-bodied, between 1/4 to 1-1/2 inches long, greenish, yellow, brown or black, somewhat flattened and wings lay flat on the body when at rest. Wings have many veins and both pairs are about equal in size. The abdomen is soft, bearing a pair of cerci at the end. They have a long tapered antennae. They are poor fliers, found near water and are attracted to lights. Some adults emerge in cold weather from November to March, become active on warmer days (early in the year) when they mate and live only a few weeks. The nymphs (naiads) live in flowing streams, under stones or gravel (one to three years). They feed on vegetable matter and other insects. Stoneflies in the immature stage are fed upon by game fish, being of great economic importance. Anglers refer to stoneflies as "browns" and copy them in wet and dry flies.
Adults are between 1/4 to 1/2 inches long, soft-bodied, elongate and have two or three long, many-jointed, threadlike "tails" at the end of the abdomen. They are pale yellow with brownish stripes with a reddish-brown thorax. The large triangular, membranous forewings have many longitudinal veins and cross veins with the hindwings quite small or lacking. At rest, the wings are held together, erect and above the body. Antennae are very short (inconspicuous) and legs are short and weak. They are attracted to lights and usually found around streams. Adults do not feed and live only a few hours or at most a day or two. They may emerge in huge numbers from lakes and rivers, piling up along the shore or nearby roads sometimes a few feet deep. The nymphs (naiads) live in clear, fresh water feeding on vegetable matter for a year or more. Mayflies are very important, serving as food for fish and birds. Anglers imitate the adults in dry flies, referring to them as "spinners" or "duns" and pattern wet flies after the nymphs.
Adults are about 1/4 inch long, somewhat flattened, oval, gray-brown or mottled with the top surface often finely cross-lined and the hind legs elongate and oarlike (flattened and fringed with hairs) for swimming. Eyes are black (space between yellow) and legs and body underparts yellow. They swim rapidly, usually seen at the bottom in shallow water of ponds and lakes, and feed on algae, protozoa, plankton or dead organic matter on the bottom of pools and roadside ditches. Some species are attracted to lights and swarm around them. Their life cycle takes about six weeks from egg to adult in the life cycle. They overwinter as adults. Some are sold for bird and fish food. They do not bite.
Adults are about 1/2 inch long, black and white colored, swim upside down on their backs, have triangular-like (boat-shaped) bodies, and large eyes. They are kidney shaped, with a four segmented beak, and antennae in three to four segments concealed between the head and thorax. There is an irregular brown and blackish band across the wings at the base of the membranous portion. The front and middle legs are fitted for grasping while the hind legs are flattened, fringed and fitted for swimming. They are often seen on the water surface with their long hind legs held straight out and pointed forward, poised for a fast start. They live in all kinds of water (fresh to scum-covered stagnant) and overwinter as adults. They fly long distances, often in swarms and are attracted to lights. The life cycle requires about 40 days. They feed on insects, tadpoles and small fish. They can bite, causing pain much like a bee sting when handled carelessly.
Adults are large (2 to 2-1/2 inches long), brownish, somewhat flattened, and broad with the middle and hind legs fitted for swimming. The front legs are fitted for grasping (praying mantis-like) with two claws at the tips. The end of the abdomen bears two short, strap-like appendages for breathing. The head is broad and slightly extended beyond the eyes. They are very much attracted to lights and are known as "electric light bugs." Sometimes they leave the water and fly to street lights some distance away. These bugs feed on other insects, snails, tadpoles and small fish (sometimes several times their size). They inject a poisonous fluid into their prey after capture, sucking them dry. They occur in ponds and quiet pools, feigning death when removed from the water and ejecting a fluid from the anus. Death is quick if not able to return to the water. Eggs are laid in massed rows of 100 or more above the water on cattails and other plants, hatching one to two weeks later. They are vicious biters, inflicting pain when handled carelessly.
Adults are between 5/16 to 5/8 inch long, dull to grayish or reddish brown above and silvery gray on the underside of the body. Many have long slender bodies with long, slender legs and antennae. The front legs are short and modified for grasping while the middle and hind legs are long, like stilts with claws. These insects creep on the surface of running water or pools in a slow deliberate gait where they feed on live and dead insects, crustacea and other organisms. They overwinter as adults. Long, cylindrical eggs are laid during spring and summer in parallel rows glued to objects at the water's edge. Adults are called "skaters" or "Jesus Bugs," apparently for their ability to walk on water of ponds, lakes and streams.
Adults are large about 1-1/2 inches long, hard-bodied and elliptical with triangular yellowish markings on the abdomen sides. The body top is smooth and shiny black with a greenish tinge. A long spinelike keel on the thorax underside between the legs can be jabbed into the fingers when the beetle is handled carelessly. Antennae are club-shaped and the legs are flattened for swimming. They are good fliers, and are very much attracted to lights in large numbers in the spring. Beetles are commonly seen swimming or crawling among water plants or on the bottom of shallow pools, feeding mostly on dead or decaying vegetation. The hind legs move alternately when swimming. Larvae are predaceous and cannibalistic. There are one to two generations per year.
Adults are 3/8 inch long or slightly longer, oval, flat, hard bodied with a shiny black bronze sheen. The legs are brownish yellow. Eyes are divided into two widely separated parts; the upper one is oval and remains above the water and the lower one is somewhat smaller and remains below the water. These fast-moving beetles are often seen swimming in groups in endless gyrations or circular "skating" movements, in a spot on the water surface. The outer margins of the wing covers are curved inward near the tip. The legs are flattened, fitted for swimming and the antennae are quite short with the last segment enlarged. They are found in lakes, ponds and streams. The adult scavengers and the larvae are predaceous and aquatic. Larvae leave the water to pupate on bordering plants and overwinter as adults. There is one generation per year.
Adults are 1/4 to 1-3/16 inches long, ovate, smooth, and have shining black bodies. There is a yellow margin around the front of the head, sides of the thorax and wing covers. Antennae are threadlike and prominent, with the hind legs longest and flattened to serve as oars in swimming. They are attracted to light, often migrate from one pond to another and are strong fliers. Unlike other water beetles which move their legs alternately when swimming, these beetles stroke them together like oars as the backswimmer bugs do. They can be collected by sweeping submerged vegetation in streams and ponds with a dip net. Both adults and larvae are predaceous. Sharp hollow mandibles (jaws) are used to inject paralyzing and digestive fluids into their prey and to draw out the liquid contents. They attack aquatic insects and fish, and have the ability to regenerate lost parts to some extent. Larvae crawl to shore to pupate in the soil and hibernation occurs in the water as an adult or larvae. There is one generation per year, and adults can live several years.
Since many nuisance aquatic insects are attracted to mercury vapor lights, it is important to use lights sparingly in and around the swimming pool and other areas where insects are not wanted. Use special high-pressure sodium vapor yellow lights which are less attractive to insects and more energy efficient. Set lights 20 to 30 feet from the swimming pool (directing the light to the pool), if practical. Remember that less light equals less insects. Never use 150 watts of light when 25 watts are adequate. All light attracts insects for warmth and ultraviolet energy. Insects are cold-blooded and they see and respond best to ultraviolet energy mercury vapor light. Use long-handled dip nets daily to gather insects, leaves and other debris falling into the water. Maintain good sanitation through proper filtration, chlorine treatment and cleaning. Prevent slime buildup and empty small children's pools when not in use. When on vacation for two or more weeks, either drain the pool or have someone provide maintenance. Some use pool covers. Keep shrubs and grass trimmed closely, especially adjacent to the pool. Increasing the chlorine content to kill the insects could make it harmful for swimmers to use.
Most aquatic insects die rather quickly unless they can return to water. Insecticide control is rarely needed. Never use insecticides in swimming pools due to possible harmful effects on the swimmers and wildlife. Pyrethrin spray used around lights will give temporary knockdown of some flying insects and some repellency. Collect and discard dead, dying and stunned insects with a broom and dust pan, vacuum cleaner, etc. Shrubs and bushes away from the swimming pool can be sprayed lightly with resmethrin plus piperonyl butoxide a few hours before any recreational event to reduce nuisance insects. Avoid contamination of the swimming pool with insecticide spray drift. Before using any pesticide, always read the label. Follow directions and safety precautions.
This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and Ohio State University Extension assume no liability resulting from the use of these recommendations.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-6181