Gerridae

Some bugs walk on top of water.

They are called water striders. They have very long legs. These legs spread their weight out. This helps them stay up.

Tiny hairs cover their bodies. These hairs push water away. This keeps the bugs from getting wet. If they fall in, the hairs trap air. The air helps them float back up. They use their middle legs to row. This helps them zip across a pond.

They are very fast swimmers.

Water striders are small bugs that live on water.

Most live in fresh water like ponds and rivers. Some live in the ocean. They have long legs to help them move.

These legs spread their weight out. This helps them stay on top of the water. Tiny hairs cover their bodies. These are called hydrofuge hairs. They push water away so the bug stays dry. If a wave pushes them under, the hairs trap air. This air helps them float back up.

Water striders use their legs to move. The middle legs are the longest. They use them like oars to row. The back legs help them steer. They can move very fast. Some can go one meter every second.

These bugs can have wings or not. This is called wing polymorphism. This means a species can have different wing types. Some bugs have long wings to fly to new places. Others have no wings. Having no wings lets them save power. They use that power to make more eggs instead.

Water striders belong to a family of insects called Gerridae.

People call them many names, like pond skaters or water skimmers. Most of these bugs live in fresh water, like lakes and rivers. However, about 10% of them live in the salty ocean. One special group called Halobates lives in the sea.

These insects are amazing because they live on the very top of the water. This way of living is called being a pleuston. They use the water's surface like a floor to walk on.

To stay on top of the water, they use a special way of working.

First, they have long, slender legs that spread their weight out. This helps them stay above the surface tension of the water. Their bodies are covered in tiny hairs called hydrofuge hairpiles. These hairs repel water so the bug does not get heavy and sink.

If a wave pushes them under, these hairs trap tiny air bubbles. These bubbles act like a life jacket to bring them back up. To move, they use their long middle legs like oars to row. They can even move at a speed of one meter every second.

Scientists have studied these insects for a long time.

An explorer named Eschscholtz discovered three species of Gerridae early on. Later, Francis Buchanan White studied them during the Challenger expedition between 1822 and 1883. We now know that this family likely began about 128 million years ago. This was during the Cretaceous period. They are related to another group called Veliidae. Both groups share a similar way of rowing through the water.

There are many different types of water striders with unique facts.

There are over 1,700 different species that scientists have described. Most species have bodies that are between 2 and 30 millimeters long. A large genus called Aquarius lives in the Northern Hemisphere. In the streams of Vietnam and China, a species called Gigantometra gigas lives. This bug is quite large, reaching 30 millimeters in winged females. In this species, the middle and back legs can even grow longer than 30 millimeters.

Water striders can also change how they look to survive.

This is called wing polymorphism, which means having different types of wings. Some water striders have long wings so they can fly to new ponds. Others have short wings or no wings at all. Having no wings helps them save energy for making more eggs. This is a smart way to adapt to changing seasons. They can use the extra energy to help their babies grow faster. This helps the whole group stay strong in their habitat.

The Gerridae are a diverse family of insects known commonly as water striders.

They belong to the order Hemiptera and the suborder Heteroptera. These insects are true bugs, meaning they have mouthparts designed for piercing and sucking. A defining characteristic of the Gerridae is their ability to live on the water's surface. This lifestyle makes them pleuston, or surface-living animals. They can be found in many environments, including ponds, rivers, and lakes. While 90% of these insects live in freshwater, about 10% are marine. The genus Halobates is a notable exception because it lives in the ocean.

To stay afloat, water striders utilize the high surface tension of water. They use long, slender legs to distribute their body weight over a large surface area. This prevents them from breaking through the water's surface. Their entire bodies are covered in hydrofuge hairpiles. These are tiny, hydrophobic microhairs with more than one thousand hairs per millimeter. These hairs repel water and prevent droplets from weighing the insect down. If a wave pushes a strider underwater, these hairs trap air. The trapped air creates tiny bubbles that provide buoyancy to bring the insect back up. This position, where the body stays mostly above the water, is called epipleustonic.

Movement for a water strider is a complex mechanical process. They have three pairs of legs: front, middle, and hind. The front legs are the shortest and feature preapical claws. These claws are located halfway down the leg rather than at the very end. These are used to puncture prey. The middle legs are the longest and are used for propulsion and steering. They have well-developed fringe hairs on the tibia and tarsus to increase thrust. During a rowing stroke, the middle tarsi are pressed down and backward. This action creates a semicircular surface wave. The strider uses the crest of this wave as a counteracting force to push forward. This allows them to move at speeds of 1 meter per second or faster.

The Gerridae exhibit a fascinating trait called wing polymorphism. This means a single species can have different types of wings. Some populations are long-winged, or macropterous, while others are short-winged or entirely wingless, or apterous. This is often explained by the oogenesis-flight syndrome. Developing short wings allows an insect to save energy. Instead of building wing muscles, they use that energy for egg production. This increases their reproductive success and fitness. Long wings allow for dispersal to new water bodies if a current habitat becomes crowded. Short wings allow for limited travel. Wingless forms are ideal for stable habitats where the environment does not change much. An environmental switch mechanism, influenced by temperature and photoperiod, helps control these seasonal changes.

Scientists have studied the history and evolution of these insects for a long time. Molecular analysis suggests the family originated about 128 million years ago during the Cretaceous period. They split from a sister group called Veliidae. Both groups share a single origin of rowing as a way to move. Early researchers like Eschscholtz discovered several species, bringing attention to the family. Later, Francis Buchanan White conducted heavy studies on the genus Halobates during the Challenger expedition between 1822 and 1883. These studies helped scientists understand how these insects occupy unique ecological niches.

There is significant variety in the size and shape of Gerridae species. Most species have a body length between 2 and 30 millimeters. The genus Aquarius in the Northern Hemisphere includes some of the largest species. In the streams of northern Vietnam and southern China, the species Gigantometra gigas lives. This species is quite large, with winged females reaching about 30 millimeters. In this specific species, the pattern of size is reversed, as females are usually larger than males. Some males can even reach 30 millimeters in length. Their middle and hind legs can also exceed 30 millimeters in length.

The life cycle of a water strider involves several distinct stages. Females lay eggs on submerged vegetation or rocks using a gelatinous glue. A gravid female may carry between two and twenty eggs. The eggs are initially creamy white or translucent but turn bright orange later. After the egg stage, the insect goes through five instar stages as a nymph. Each nymphal stage typically lasts between 7 and 10 days. During these stages, the insect molts by shedding its old cuticle. Nymphs look similar to adults but are smaller and paler. They eventually reach the final adult stage to complete their development.