Water Boatmen belong to the family Corixidae, a large group of true bugs found in freshwater ecosystems worldwide. They are easily recognizable by their streamlined, flattened bodies, typically less than 13 millimeters long, and their long, fringed hind legs used like oars for swimming. Water Boatmen are often confused with Backswimmers (Notonectidae), but their swimming posture differs: Water Boatmen swim right-side up, usually near the bottom, while Backswimmers swim inverted on their backs, often near the surface. Corixidae are unusual among true bugs because they are not predators; they feed mainly on algae and detritus, which they scoop up with specialized, spoon-shaped front legs.
Global Distribution and Preferred Habitats
Water Boatmen are a cosmopolitan group, found globally in a wide array of climates, from sub-arctic regions to the tropics. They inhabit nearly any body of still or slow-moving fresh water, including ponds, lakes, ditches, and quiet areas of streams. Some species are highly adaptable and can tolerate slightly brackish or saline water, such as that found in salt marshes.
Their presence is closely linked to the availability of submerged vegetation and organic material. Water Boatmen prefer habitats where plants are plentiful, as this offers both cover from predators and a stable surface for foraging. They are commonly found near the bottom, where they stir up sediment to feed on microscopic organisms and plant matter. This preference for vegetated, calm waters allows them to thrive in both natural ponds and man-made pools.
The Reproductive Cycle
Water Boatmen originate through incomplete metamorphosis, which occurs entirely within their aquatic habitat. The cycle begins when the adult female lays fertilized eggs, typically during spring and summer. These eggs are securely cemented to submerged objects, such as aquatic plants or rocks.
After a few weeks, the eggs hatch into nymphs, which are miniature, wingless versions of the adult. The nymph stage involves growth through several intermediate stages, called instars. To accommodate this growth, the nymph must repeatedly shed its exoskeleton through molting. The final molt results in a fully-formed, winged adult capable of reproduction and dispersal.
Methods of Migration and Arrival
The sudden appearance of Water Boatmen in isolated locations, such as a backyard swimming pool, results from their strong flight capabilities. Adult Water Boatmen possess functional wings and fly when their current habitat becomes overcrowded, dries up, or faces adverse conditions. This dispersal flight is a regular, seasonal migration for many species, allowing them to colonize new or temporary water sources.
They use the pattern of polarized light reflecting off the water’s surface to locate new bodies of water. Unfortunately, this reliance often leads to navigational errors, as they mistake highly reflective, horizontal surfaces for water. Examples include wet asphalt, dark car roofs, and the smooth bottoms of swimming pools, explaining their unexpected arrival in artificial environments. Once they land, they use their long, oar-like hind legs to propel themselves through the water.