The water strider, a familiar inhabitant of freshwater surfaces, is a highly adapted insect belonging to the family Gerridae. Commonly known as pond skaters or water gliders, these small creatures are found on the still or slow-moving waters of ponds, lakes, and streams worldwide. This adaptation allows them to fill a specific ecological niche, acting as both predators and scavengers on the surface layer.
Identifying the Water Strider
Water striders possess a distinct body shape characterized by a slender torso and three sets of elongated legs. Their middle and hind legs are significantly long, serving as the primary means of propulsion, while the shorter front legs are adapted for grasping prey.
The entire body and legs are covered with thousands of microscopic, non-wetting hairs that are strongly hydrophobic, meaning they repel water. This superhydrophobicity, combined with the insect’s light weight and the wide distribution of that weight across its legs, allows the water strider to exploit the surface tension of the water. They do not break the water’s surface film, instead creating small depressions, or menisci, that support their weight. They move by using their middle legs in a rowing motion, pushing against the surface tension to glide or “skate” across the water.
The Primary Diet
Water striders are opportunistic feeders whose diet consists almost entirely of invertebrates trapped on the water’s surface. They function as both active predators and scavengers, consuming any insect that falls into the water and becomes unable to escape. This includes terrestrial insects like ants, flies, and beetles that accidentally fall from nearby vegetation.
Their feeding habits also help control populations of aquatic insects during their emergence stages. They commonly prey on mosquito larvae and pupae, as well as midges and small dragonflies, just as they try to break through the water surface. Water striders prefer live prey, but they will readily scavenge dead or dying organisms that float on the surface.
Hunting and Feeding Mechanisms
The water strider’s hunting strategy relies on its sensitivity to surface vibrations created by struggling prey. Their legs act as highly specialized sensors, detecting the smallest ripples that radiate outward from a trapped insect. These ripples, or capillary waves, are interpreted by the strider to determine the prey’s location, size, and movement pattern, enabling them to quickly zero in on the source.
Once the prey is located and secured with their shorter forelegs, the water strider uses its specialized mouthpart, known as a rostrum or beak, for feeding. This rostrum is a piercing and sucking structure that is folded beneath the head when not in use. The insect pierces the outer cuticle of its meal and injects salivary enzymes into the prey’s body. This process of extra-oral digestion dissolves the internal tissues of the prey, turning the contents into a liquid, which the strider then sucks out through the rostrum, leaving behind an empty exoskeleton.