Backswimmers and water boatmen are two fascinating aquatic insects that are often confused due to their similar appearance and habitat.
They belong to the order Hemiptera, commonly known as “True Bugs”, and can be found in various freshwater habitats such as ponds and lakes.
While both insects are boat-shaped and less than 1/2″ long, they come from different families and exhibit distinct behavioral and physical characteristics.
The backswimmer is known for its unique swimming style – it spends its life rowing around belly-up, with a dark belly and a light back.
In contrast, water boatmen are typically a bit smaller than backswimmers and swim along the bottom of the pond with their head down.
They possess different mouthparts and diets; water boatmen lack the standard piercing beak and instead ingest living material like diatoms, while backswimmers are predatory and use their beaks to catch and feed on other small aquatic insects or arthropods.
Backswimmer vs Water Boatman
Appearance and Identification
Here are some visual differences to help identify them:
Backswimmer (Notonecta glauca): Characterized by its dark belly and light back, backswimmers have an oval shape and swim with their ventral side (belly) facing upwards 1.
Water Boatman (Family Corixidae): Smaller than backswimmers, these bugs have slender, oval bodies, and red-eyed appearance.
Their hind legs are scoop or oar-shaped, and they swim head-down along the pond bottom searching for food 2.
Differences in Habitat
Both backswimmers and water boatmen reside in freshwater habitats; however, they inhabit different areas within these environments:
- Backswimmers: They are usually found swimming freely on the water surface as they prefer open water habitats.
- Water Boatmen: They tend to dwell near the pond or lake bottom, where they can scavenge for food sources.
Here are the differences in feeding habits between backswimmers and water boatmen:
- Backswimmers: These insects are primarily carnivorous, preying on small aquatic insects, larvae, and even small fish. They use their sharp mouthparts to pierce and kill their prey.
- Water Boatmen: They feed on living materials, such as diatoms, algae, and detritus3. Lacking the standard piercing beak of other aquatic true bugs, water boatmen instead ingest their food sources.
|Coloring||Dark belly and light back||Slender, oval, often red-eyed|
|Habitat||Open water surface||Pond or lake bottom|
|Feeding Habits||Carnivorous (insects, larvae, fish)||Herbivorous (diatoms, algae, detritus)|
Classification and Family Relations
The family Notonectidae, commonly known as backswimmers, belongs to the order Hemiptera.
These invertebrate creatures are identified as true bugs and are known for their unique swimming style.
They swim upside down and are characterized by their aggressive piercer-predator behavior.
Some features of Notonectidae:
- Prey on invertebrates and small vertebrates
- Use their piercing mouthparts to suck out bodily fluids
- Compete with small fish for food, but can also be prey for larger fish
On the other hand, water boatmen, belonging to the family Corixidae, also fall under the Hemiptera order.
Despite sharing the same order, water boatmen are quite different from backswimmers.
They are not predators, instead, they feed on algae and other organic materials in the water.
Some characteristics of Corixidae:
- Primarily herbivores
- Known for their rowing movement through the water
- Less aggressive than backswimmers
A comparison table of Notonectidae and Corixidae:
|Notonectidae (Backswimmers)||Corixidae (Water Boatmen)|
|Movement||Swim upside down||Rowing movement|
|Food Chain||Compete and be eaten by fish||Coexist with fish|
Front Legs and Hind Legs
Backswimmers and water boatmen utilize different legs for varied purposes. For instance:
- Backswimmers: their front legs are for capturing prey, while their long, oar-like, hair-covered hind legs are for efficient swimming.
- Water boatmen: their front legs are adapted for crawling on submerged surfaces, whereas the flattened third pair of legs help in underwater rowing motion.
Covered Hair Troughs for Storing Air
Both backswimmers and water boatmen possess covered hair troughs that enable them to store air for breathing underwater.
These troughs are crucial for their survival.
Backswimmers and water boatmen have distinct ways of swimming:
- Backswimmers: swim upside down, with their specially adapted oar-like hind legs propelling them.
- Water boatmen: use their flattened third pair of legs as paddles, allowing them to row through water with ease.
|Front legs||Capture prey||Crawling underwater|
|Hind/Third pair legs||Oar-like, swimming||Flattened, rowing|
|Troughs||Store air||Store air|
|Swimming position||Upside down||Right side up|
Diet and Feeding Habits
Backswimmers are piercer-predators that are known to feed on a variety of prey, including:
- Tiny fish fry
- Small insects
These aquatic bugs compete with small fish for food sources. They kill their prey by piercing them and sucking out the bodily fluids.
Water Boatman Food Sources
Water Boatmen are different from Backswimmers because of their food consumption habits.
They lack piercing beaks. Instead, they ingest living material, including:
In addition to these microscopic creatures, Water Boatmen have also been known to feed on algae, mosquito larvae, and small fish eggs.
Their feeding helps maintain dissolved oxygen levels in the water bodies they inhabit. Here is a small comparison table of the two:
|Prey||Fish fry, tadpoles, small insects||Protozoa, diatoms, nematodes|
Life Cycle and Reproduction
- Backswimmers engage in a unique mating process, whereby the male grasps the female’s thorax with his forelegs.
- The male then produces ultrasonic mating calls to attract the female and initiate copulation.
- Water boatmen use their modified hind legs to produce sounds by rubbing them against their abdomen.
- Their mating ritual involves the male climbing on the female’s back for a short period.
Egg-Laying and Development
- Female backswimmers lay their eggs on submerged plants or floating debris.
- The aquatic nymphs develop through a series of instars, molting their exoskeletons as they grow in size.
- Eggs are attached to underwater plants or debris by female water boatmen.
- Similar to backswimmers, water boatmen nymphs undergo a series of molts before reaching adulthood.
|Lays eggs on||Submerged plants||Underwater plants|
|Nymph development||Instar series||Instar series|
|Mating call||Ultrasonic calls||Rubbing hind legs|
Both backswimmers and water boatmen can be found in different habitats, such as ponds, lakes, and slow-moving streams. These habitats provide them with suitable locations for their egg-laying and development processes.
Interactions with Environment
Aquatic Ecosystem Roles
Backswimmers and water boatmen are both insects that can be found in various aquatic environments like ponds, lakes, bird baths, and even sewerage ponds. They have different roles in these ecosystems:
- Backswimmers: These insects are predators that feed on other aquatic animals such as mosquito larvae and small fish.
- Water boatmen: They are mostly herbivorous and feed on aquatic plants and living material like algae.
Their presence in water bodies can have an impact on the populations of aquatic animals and plants.
For example, backswimmers can help control mosquito populations in stagnant water by preying on their larvae.
Pest or Beneficial Insects?
Both backswimmers and water boatmen can be seen as a pest or beneficial insect, depending on the situation.
- Backswimmers: Their painful bites can cause discomfort to humans, making them undesirable around populated areas such as lake edges or pond-side parks.
- Water boatmen: In some cases, their feeding habits can negatively affect the health of aquatic plants.
- Backswimmers: As mentioned earlier, they help control mosquito populations by preying on their larvae, which can be beneficial in reducing the spread of mosquito-borne diseases.
- Water boatmen: By feeding on algae and other living material in water bodies, they can help with water clarity and overall aquatic health.
If you have a pond near your home, having a small population of water boatmen can be beneficial to maintain the health of aquatic plants and improve water quality.
|Aquatic Ecosystem Roles||Predators||Herbivorous|
|Pest||Painful bites||Plant damage|
|Beneficial||Mosquito control||Water clarity|
Backswimmers and Water Boatmen: Human Experience
Interestingly, both backswimmers and water boatmen have been consumed by humans in various cultures:
- Egyptian: Water boatmen are a part of some Egyptian dishes
- Mexican: Backswimmers are considered a delicacy in some Mexican cuisine
Although these aquatic insects may seem unimportant, they have cultural significance and have been mentioned by various researchers, such as Dr. Gilbert Waldbauer, who studied their roles in aquatic ecosystems.
To summarize, while backswimmers and water boatmen both have oval-shaped bodies, long legs, and one pair of wings, they are very different in other ways.
Backswimmers swim upside down and have a keeled back, while water boatmen swim right side up and have a flat back.
Backswimmers are predators and prey in the aquatic food chain, while water boatmen are mostly herbivores and detritivores.
Backswimmers can bite humans if handled or disturbed, while water boatmen are harmless to humans.
Backswimmers and water boatmen are interesting and important animals that reflect the diversity and adaptation of life in water.
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about both backswimmers and water boatmen. Scroll down to have a look at some of them.
Letter 1 – Backswimmer AKA Water Wasp
I found this bug in our pool, and after it freaked out the kids and I fished it out, I looked on your site. Sure enough, you had one picture of it, under True Aquatic Bugs.
I thought perhaps maybe a few other pictures of a Backswimmer might be of use to you. Thanks for helping me identify it.
Also, can’t the Chlorine, or other chemicals in the pool water, kill the bug? Thanks again,
Thanks for sending us another photo of a Backswimmer. One nagging reader, a Truly Candid Girl, might be annoyed, but we haven’t posted a new photo of a Backswimmer in quite some time.
Backswimmers are in the Family Notonectidae, and more information can be found on BugGuide where we just noticed the common names Water Bee or Water Wasp, undoubtedly a reference to the bite.
The chlorine would probably need to be at a very high concentration to harm the Backswimmer, though the lack of prey like small aquatic insects and other invertebrates will ensure that Backswimmers will not permanently inhabit your pool. Since they fly, they can come and go at will.
Letter 2 – Backswimmer
Subject: Sry for another request but I like to know the critters I shoot are….
Location: Ypsilanti MI
February 18, 2013 12:59 pm
This water beetle was in my pool last summer 2011. It was really cool to watch dive under with its air bubble on its back…is this a diving beetle? :/
Signature: Rachel R
This is not a beetle, but rather, it is an aquatic True Bug, a Backswimmer, most likely in the genus Notonecta. Because of the painful bite, they are commonly called Water Bees or Water Wasps according to BugGuide.
Im glad Im askin cus Ive been wrong twice now lol Thank you soo much for the info on my critter pics :)) :)) Great site for bug info:))
Letter 3 – Backswimmer
Subject: Crazy Gorgeous Beetle
Location: Calgary Alberta Canada
July 13, 2013 5:58 am
I found this guy on my car. He was about an inch long if I remember correctly. It was spring close to summer in Calgary, Alberta Canada.
Signature: A hodge
Dear A hodge,
This is an aquatic insect known as a Backswimmer. Those long hind legs propel the Backswimmer through the water like oars as it swims up-side-down. Backswimmers are also capable of flying from one body of water to another.
Backswimmers can deliver a painful bite if carelessly handled or if accidentally encountered while swimming, so they are sometimes called Water Wasps. See BugGuide for more information on Backswimmers.
Wow! Thanks for the fast response! Glad I didn’t touch him! Andrea.
Letter 4 – Backswimmer bites insect fan
Subject: Too much of a good thing?
Location: Grand Island, Nebraska October 14, 2012
October 15, 2012 9:59 pm
Your wonderful website has fostered in me a curiosity about bugs that has been passed along to my daughters, ages 6 & 12. Unfortunately, in her enthusiasm to show me a new bug, my 12 year old brought this insect to me in her hand.
It promptly bit/stung her and she dropped it into the sand where I took this picture. There were others in the area as well and they seemed to be quite adept at hopping. I’ve looked through pages and pages of flies but have been unable to find anything similar to this one.
We have appreciated your help in the past and would love it if you would help us solve our latest mystery. Thanks!
Signature: Huskers Kim, Rachel & Emma
Dear Huskers Kim, Rachel and Emma,
We hope this unfortunate incident has not cooled your family’s enthusiasm for the insect world. This Backswimmer in the genus Notonecta is actually an aquatic insect that is capable of flying from one body of water to another.
According to BugGuide, Backswimmers are also called Water Bees or Water Wasps because of the painful bite. Some information provided by BugGuide includes: “Prey on other aquatic insects and sometimes on small vertebrates” and “May bite if handled carelessly.”
Letter 5 – Backswimmer from Ireland
Subject: What’s that bug?
Geographic location of the bug: Dublin, Ireland
Time: 01:04 PM EDT
Your letter to the bugman: Hi, I just found the attached on my kitchen floor and I was wondering if you could identify it please? I think it may have dropped onto the floor from an open Velux window directly above. I currently have it under a large upturned glass.
It does have wings and occasionally tries to fly. It’s about 2 – 3 cm long. The rear legs are markedly longer and wider than its other limbs.
The temperature here is currently 25 Celcius, in case that matters?
Many thanks for any information you can give me!
How you want your letter signed: Mark Walsh
This is an aquatic True Bug commonly called a Backswimmer, and like many aquatic True Bugs, it can fly quite well, an adaptation that is quite helpful in the event a pond or swamp it is living in happens to dry out. Based on images posted to Nature Spot, it appears it is the Common Backswimmer, Notonecta glauca, and the site states:
“Up to nearly 2 cm in size, and commonly called backswimmers because they swim upside down and are often seen at the surface of the water. Notonecta glauca is light brown in colour with a number of dark markings and large reddish eyes.
It often looks silvery as air becomes trapped in a layer of bristles covering the lower surface. The powerful oar-like hind legs are modified for swimming; they are long, flattened and fringed with hairs”
The site also states: “Backswimmers are predators that attack prey as large as tadpoles and small fish, the forelegs, which are short and strong, are used for grabbing prey.”
Like other predatory True Bugs, they have mouths adapted to piercing and sucking fluids from prey, but they are also capable of biting unwary swimmers, leading to common names like Water Bees or Water Wasps, according to the North American site BugGuide which also notes:
“Come to lights; may invade swimming pools and become a nuisance.” According to UK Safari: “Adult Backswimmers are able to fly. They hunt their prey by floating motionless on the water surface.
When they detect movement in the water they swim towards it to see if it is worth catching. The bite from a Backswimmer can be painful as their saliva is toxic.”
Thank you very much for all that information and also for your time, much obliged.
We have had a much warmer and drier summer than usual in Ireland this year, so that really makes sense that a pond may have dried out somewhere…
Anyway, thanks again!