authored by GVM resident Terry W. Campbell, BS, MS, DVM, PhD

Water striders are harmless true bugs (Hemiptera) about half of an inch long [0.4 inch (11mm) to 0.6 inch (16mm)], that can be found living on the surface of still or slow-moving water, such as ponds, puddles, streams, creeks, lakes, and coves. They are generally brown in color. Eight species in the genus Gerris or Aquarius make Colorado their home. Aquarius remigus is the most common and prefers lotic (flowing water) habitats, such as the creek found along the Crelin nature trail.

Water striders can stand still, glide, and skip across the surface of water. They literally walk on water, due to the high surface tension of aqueous water, the hydrophobic nature of their legs, and hydrofuge hairs lining the body that increase the surface area to evenly distribute their weight across the water’s surface. If they become submerged in water, air bubbles trapped in the hydrophobic hairs will make them float back to the surface. Their long legs are splayed out from the body and tipped with the fine hydrophobic hairs that catch air to provide flotation, therefore, the insect does not break the surface tension of the water.

Being insects, they have six pairs of legs. The hind two pairs of legs are elongated. The middle pair of legs are used for locomotion like oars and move in a rowing motion, whereas the hind pair of legs are for stability. The first pair of legs are smaller and designed for grasping prey.

In general, these insects can be found in May to October. Water striders use ripples in the water to communicate with one another. Frequencies of around 25 Hz are used as a repel signal to let others know they’re too close (also by an unimpressed female to let the male know she’s not interested in mating), 10 Hz is a threat signal, and around 3 Hz is the courtship signal. The smaller males attach themselves to the back of females and will remain there for the entire duration of the breeding season, to ensure the female’s offspring are his own. Thus, providing a whole new meaning to a “clingy relationship.”

Females lay eggs just below the water’s surface where they are attached singly or in clusters to plants along the edge of the pool. The eggs hatch in two days, after which, the nymphs undergo several developmental stages until reaching adult stage in around 16 days. Adults and nymphs feed on insects and other small prey that fall into the water. Adults overwinter under leaves, logs, or holes on land.

---

Suggested reading:

Campbell V, Fairbairn DJ. 2001. Prolonged copulation and the internal dynamics of sperm transfer in the water strider Aquarius remigis. Canadian Journal of Zoology 79: 1801– 1812.

Cranshaw W, Thomas C, Kondratieff B, Walker G. 2010, Life in a Colorado Water Garden: The Insects and other Invertebrates Associated with Water Features. Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523.

Damgaard J, Christiansen P. 2007. Genital morphology and taxonomy of the water strider Aquarius remigis (Say) (Insecta, Hemiptera-Heteroptera: Gerridae). Biological Journal of the Linnean Society, 90, 381-398