Fossil Water Strider | Family Gerridae | 100% Natural | Green River Formation

Family Gerridae (Water Striders)
Eocene (51.98 Million Years Ago)
Green River Formation, Wyoming, USA

Specimen approx. size: 1.5" x 1.5"

Matrix approx. size: 3.5" x 2.25"

Family Gerridae (Water Striders)

Commonly known as water striders, Gerridae are a family of semi-aquatic insects in the order Hemiptera (true bugs). They are best known for their ability to walk and glide across the surface of water, a skill made possible by specialized physical adaptations.

General Description

Water striders have elongated, slender bodies and long, delicate legs. Their middle and hind legs are greatly elongated and used for rowing and steering, while the shorter front legs are adapted for grasping prey. Adults typically range from 2 to 12 mm in length, depending on the species.

Surface-Walking Adaptations

Their legs are covered with dense, microscopic hydrophobic hairs that trap air and repel water. This creates enough surface tension to support their weight, allowing them to remain on the water surface without breaking it. The legs also distribute body mass efficiently, preventing sinking.

Habitat

Water striders inhabit freshwater environments worldwide, including ponds, lakes, slow-moving streams, marshes, and calm river margins. Some species occur in brackish water, and a few even live on the open ocean surface (Halobates).

Feeding and Behavior

Water striders are predatory, feeding on insects and small invertebrates, like mosquitoes (especially larvae), flies, gnats, and spiders that fall onto the water surface. They detect prey through surface vibrations and capture it using their forelegs. They pierce their prey with their needle-like mouthparts (proboscis), inject salivary enzymes that break down the prey's insides, and then suck out the liquefied nutrients. Water striders prefer living prey but will scavenge matter that falls onto the water surface. In times of necessity, they may also engage in cannibalism.

They are strong skaters and can quickly dart away from predators. Many species are territorial, especially males, and display courtship behaviors involving surface tapping and vibration signals.

Wings and Life Cycle

Species may be winged or wingless, with wing development often influenced by environmental conditions such as habitat stability. Water striders undergo incomplete metamorphosis, progressing from egg to nymph to adult. Nymphs resemble smaller, wingless adults.

Ecological Role

Gerridae play an important role in aquatic ecosystems by controlling insect populations and serving as prey for fish, amphibians, and birds.