The common water strider (Gerris remigis) is a true bug that looks like a mosquito walking on the surface of the water. Reported from all contiguous 48 states, the water strider lives on the surface of ponds, marshes, slow streams and other quiet water. Possessing good vision, water striders move quickly over the water. I can vouch for their vision: the slightest body movement as I laid on the bank of Ash Creek (Lassen County CA) taking these pictures would cause all the water striders to immediately skitter away.
Water striders, also called water skippers, posses a long (about 1/2 “) thin body and six legs. The front pair of legs is short and used for grabbing prey, the middle pair pushes the strider forward and the rear set steers. The mouth parts are made for piercing and sucking the body juices from their prey. The two antennae each have four segments.
Water striders display wing polymorphism, whether or not a population has wings is variable. I will not delve into this interesting topic now. But as an example, in a habitat that is drying out, water striders can develop wings to fly off and find a new home. Alternately, water striders can burrow into the mud and become dormant during drying periods.
Water striders stay on top of the water because the shape of their legs and their light weight do not break the surface tension. Additionally water strider bodies are covered with very tiny hydrophobic (water repelling) hairs which help maintain surface tension and also prevent water droplets from weighing them down.
The diet of the water strider consists of insects, dead or alive, that live in or fall into the water – aquatics consisting of the nymphs of mosquitoes or other insects and terrestrials such as butterflies, dragonflies, beetles, worms and other species that fall into the water. In turn, the water strider is prey to predators such as fish, frogs and salamanders. Since they control insect populations and do no harm, water striders are helpful to humans.
Adult water striders overwinter under rocks, leaf litter or in other sheltered sites. In the spring the water striders communicate sexually by making ripples on the surface of the water. After mating, the female lays eggs at the water’s edge, usually on plant stems. Five nymph or instar stages follow. The instars look and act similar to adults but are smaller, paler in color and have microscopic differences. By fall the adults are ready to overwinter and begin the cycle again.
These little bugs are fun to watch as they skitter over the water in search of food.