Water Boatman Facts & Information 2021 (Corixidae)


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Water Boatman Facts & Information Guide 2021 (Corixidae)

water boatmen in a pond
Water boatmen are harmless and have feathery, paddle-like legs for swimming. Photo by Andy Reago / CC BY-NC 2.0

If you have ever gazed upon a pond or a lake and noticed a small bug that appears to be “rowing” across the surface, then you have already seen water boatmen. These small insects have long hind legs that are shaped similarly to boat oars, hence their name! When they swim, they swim on their backs near the water’s surface and look like tiny rowing boats.

Water boatmen are very common insects found all over the world – they can be found living up in the high mountains of Nepal, and in the low, hot elevations of Death Valley. They can be found in freshwater, brackish water, and salt water. While water boatmen can thrive in a variety of aquatic habitats, they are most commonly found in still freshwater ponds and quieter portions of streams and rivers. Vegetation is a very important habitat element for water boatmen, as it provides a food source and a secure surface to cling onto.

These small aquatic insects are slender and ovaline in shape, giving them an efficient body type to swim in a streamlined manner. The back legs of water boatmen are very long and “oar-like,” and covered in tiny, fine hairs. Their bodies are flattened on the backside, and adorned with many dark, narrow crosslines. They have a dark brown coloration.

kingfisher eating a water boatman
Water boatman provide a valuable food source to many organisms, including this kingfisher. Photo by Kentish Plumber / CC BY-NC 2.0

Water boatmen provide an important food source for many fish, including popular game species like trout and char.  It is a common practice among fly-fishermen and women to create lures that resemble these unique insects! Simulating the natural jerking, swimming motion of the water boatmen using the manmade lure is sure to help you catch a big one.

Interestingly, water boatmen have historically been used as a food source by humans. In Mexico and in Egypt, these insects were once considered a delicacy. In Mexico, people would plant bundles of rushes in ponds in order to attract more water boatmen to the habitat. Once the water boatmen had presumably laid their eggs, the people would come in and collect the plant matter, dry it out, and shake the eggs out of it. Once the eggs had been collected and cleaned up, they were ground up and turned into a flour substance! This water boatmen flour was then used to make “hautle,” a delicious, cake-like bread.

WATER BOATMAN FACT SHEET
COMMON NAMES
Water boatmen, Corixids
SCIENTIFIC FAMILY NAME
Corixidae
TYPE
Aquatic true bug
DIET
Detritivore, omnivore
NATIVE HABITATS
Freshwater, worldwide
AVERAGE LIFE SPAN (IN WILD)
1 year
AVERAGE SIZE
3-11 mm (3/16 – 3/8 in.)
IUCN RED LIST STATUS
Least concern

What Do Water Boatmen Look Like? (Water Boatmen Appearance)

what do water boatmen look like
Water boatmen are brown, and can have intricate lighter or darker brown crosslines, though these aren’t always present. Photo by AJC1 from UK, CC BY-SA 2.0

Water boatmen are often confused with a similar-looking insect called a backswimmer, so when it comes to identification, it is important to know what you are looking for! These two similar insects are classified into different family classes; if you know the basics of identifying water boatmen, then differentiating between these guys is fairly straightforward.

While water boatmen are rarely found in artificial water sources like pools or fountains, backswimmers frequent these areas. You will start to see more water boatmen when you take a closer look at ponds or quiet streams. Water boatmen are attracted to light, and backswimmers are not. If you think you have both kinds of insects in your area, and you want to distinguish them, bring out a flashlight at nighttime! Water boatmen will likely start showing up and wriggling around.

While water boatmen and backswimmers have a similar streamlined, ovaline body shape and long legs for rowing, backswimmers in the adult stage are typically much larger in size than adult water boatmen. Backswimmers are also more triangular in shape, and they swim upside down. Water boatmen only swim right-side up! Another way to distinguish these insects is by coloration. Water boatmen are typically brown in color, while backswimmers have a bolder patterning of black, yellow, brown, red, or white patches. Water boatmen have fine crosslines running across their backs, while backswimmers lack this feature.


Water Boatmen Habitats – Where Do They Live?

several water boatman bugs in a partially frozen pond
Water boatman can live in just about any slow-moving water, be it warm or cold, fresh or brackish. Photo by Oceanflynn, CC BY-SA 4.0

These hardy insects can truly be found all over the world! There are around 500 different species of water boatmen, all with slightly different niches. Most species of water boatmen prefer to reside in stagnant ponds, or slowly moving rivers and streams.

Within their habitats, water boatmen typically hang out near the bottom of the water column. They like to use vegetation as an anchor and for cover to help them evade predators. They are air-breathing insects, so they must come up to the water surface in order to create an air bubble “envelope” that they can store around their bodies. This bubble of air allows the water boatmen to swim up and down throughout the water column.

Water boatmen are also great at flying, so you may see them in the air creating swarms, especially during mating season in the spring and mid fall. 


What Do Water Boatmen Eat? (Water Boatmen Diet)

what do water boatman eat
Water boatmen feed on algae, detritus, aquatic worms, and other insects. Photo by S. Rae from Scotland, UK, CC BY 2.0

Other aquatic true bugs are equipped with a piercing beak that is useful for feeding, but water boatmen lack this feature that their relatives have! Instead, they are collectors and gatherers of food. They will swim with their heads down along the bottom of the water column searching for a tasty meal.

Water boatmen usually feed on living material. The majority of the diet of water boatmen consists of diatoms, algae, protozoa, nematodes, and small insects that they come across in the substrate. They can use their specialized mouthparts to suck juices and nutrients out of their food items.

On the other side of the same coin, water boatmen provide an important food source for a variety of wildlife! Many species of fish, birds, frogs, and aquatic invertebrates will prey on these insects when the opportunity arises. Their eggs are also eaten by fish and water birds. As both predator and prey, water boatmen serve as a valuable and important piece within the aquatic food web.

Are Water Boatmen Dangerous or Poisonous?

Water boatmen are not dangerous, venomous, toxic, or otherwise harmful to humans. They are peaceful creatures and simply swim about in search of small bits of macroscopic food, and will simply swim away if you come near them.


The Life Cycle of Water Boatmen

When it comes to finding a mate, some water boatmen are able to practice “stridulation.” This means that they can rub their front legs against their heads which then creates a squeaking sound. This sound is meant to attract a water boatmen mate! Crickets do this as well by rubbing their front wings together to create the familiar, high-pitched chirping sound that many of us are so familiar with during the warm, summer months.

Water boatmen spend a lot of time in the air during mating season, creating swarms consisting of thousands of individuals just above their pond or stream habitat. After the mating process has ended, the female will dive back into the water to lay her eggs among the plant matter growing in the substrate.  After a short time period of 1-2 weeks, the eggs will hatch into small nymphs.

Water boatmen undergo “incomplete metamorphosis,” which is a style of insect development that is characterized by gradual changes in the insect from the egg to the adult stage. Under ideal environmental conditions, water boatmen can produce multiple generations in a single year.

The life cycle of the water boatmen has three developmental stages. After hatching, a water boatman begins its outside life in the nymph stage. After several weeks of growth and development in this stage, a nymph will metamorphose into an adult. Adult water boatmen have fully developed wings and are capable of flight. During the spring and summer months, adult water boatmen are most active and begin the mating process once again.


How to Attract Water Boatmen to Ponds? Are They Beneficial?

water boatman swimming among vegetation
Water boatman prefer water with vegetation for them to eat, and help them hide from predators. Photo by Kentish Plumber / CC BY-NC 2.0

Water boatmen can be very beneficial to have around in your backyard pond as they provide a food source for fish and wildlife, and they also help to keep algal and plant growth under control! They are harmless to humans, and they do not sting or bite. Some species of water boatmen are known to feed on mosquito larvae – keeping mosquito populations down in and around your pond and house is another service that water boatmen might provide you!

These insects are highly efficient fliers, so if you do not have them in your pond already, they are fairly likely to fly in of their own accord. If you want to try to bring them in, attracting them is fairly simple and straightforward.

Because water boatmen are highly active at night and attracted to lights, putting some lights in, near, or around your pond that will turn on at dusk might prove to be very effective. If conditions are right (remember, water boatmen are not picky!) then they are likely to establish a home in your backyard pond. Having some vegetation growing in your pond already is important to have as a habitat element in order for water boatmen to establish, but these insects can thrive under a wide variety of pH and oxygen levels.

Attracting water boatmen to your backyard pond will improve the conditions from many aspects – your backyard fish and wildlife will reap the benefits, and the vegetative state of your pond will likely improve greatly!

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