Upside down, keeled like a hull, and it does bite.
First checkWhich way up? Belly upwards, on a body keeled down the back, is a backswimmer. Then check the mouth is a beak, not jaws — that is what makes it a bug and not a beetle.
A backswimmer swims on its back. Two independent sources state it plainly — belly-up, ventral side facing upwards — which makes it the settled half of a pair that is otherwise easy to muddle. Its back, which is underneath while it swims, is keeled like the bottom of a boat, and carries a dark V-shaped mark rather than the ruled crosslines a water boatman has.Dispute
It is also the predator of the two. Grasping front and middle legs, piercing tube-like mouthparts, large eyes set close together on top of the head, and an ambush habit — holding on to vegetation and waiting. It preys on aquatic insects and on small fish and tadpoles, and one extension account adds fish eggs and fry to the list. It will deliver a bite if you handle it, which Missouri says a water boatman will not do.MDC-BACKSWIMMERS, EPA-MACRO-TIPSHEET, UWM-BOATMEN-BACKSWIMMERS, UF-BACKSWIMMER-EENY738, MDC-WATER-BOATMENDispute
The thing to be careful of is the surface posture, because it is the character most people use and it does not work. A backswimmer rests tilted head-down with the tip of its abdomen through the film — and a predaceous diving beetle, per the same publisher, hangs head downward with the tip of its abdomen protruding from the water surface. Identical description, different order of insect. Use the mouth: beak or jaws.MDC-BACKSWIMMERS, MDC-DIVING-BEETLESDispute
The tell
What settles it, and what settles against it.
Read off this record's own diagnostic weights, heaviest first. A structure near the top of the left column does most of the work on its own; one near the bottom only leans.
Argues for Backswimmers
Swims on its back, belly upwards+8
One pair of long, flattened, oar-like hind legs used to row+6
Mouthparts form a pointed beak rather than chewing jaws+6
Air bubble or silvery film carried under water (diving beetle / water beetle)+3
No long tail filaments visible+2
Wings held flat and parallel along the body+1
Winged insect at or near the surface+1
Argues against it
Hard wing covers (elytra) meeting in a straight line down the back-5
Fish-shaped forage silhouette (minnow / shiner / fry) — not an insect-5
Fallen terrestrial insect (hopper, ant, beetle, etc.) — not an aquatic emergence-4
Hopper / grasshopper silhouette — hind legs long, body blocky, wings folded along back-4
Pinched waist (ant / flying ant) with elbowed antennae-4
Portable case or case-like structure present-4
Three tail filaments clearly visible-4
Plate-like or feather-like abdominal gills visible-4
Extendable grasping mouthparts (labium / mask) on an aquatic nymph-4
Three leaf-like caudal lamellae at the tail (damselfly nymph) rather than round filaments-4
Two long antennae-4
Fleshy lobes or a disc at the blunt rear end-4
Head withdrawn into the front of the body, hard to see-4
A single tail filament pointing straight back, and no paired hooks-4
Two tail filaments clearly visible-3
Gills at the thorax or leg bases-3
Hardened head with softer worm-like abdomen-3
Terminal prolegs or hooks at the rear-3
Wings held upright (sailboat posture)-3
Wings held tent-like or inverted-V over body-3
Moving as a school or tight bait cluster, not as a single insect-3
Swollen rear end gripping a rock in current, body standing up and waving downstream-3
Aquatic insect crawling on rock or debris-1
A structure at −4 or below is treated as a hard exclusion by the comparison tool rather than as a penalty: if you saw it, this group is ruled out and no amount of matching elsewhere brings it back. Run a comparison →
Life stages
What it looks like, stage by stage.
Backswimmers — Nymphdrawn
Nymph
Size in handNot given by the sources; a smaller, wingless version of the adultMDC-BACKSWIMMERSDispute
What you see
A small wingless version of the adult, swimming the same way upDispute
Wings arrive at the final moult and not beforeDispute
Where it turns up
Ponds and quiet water, clinging to submerged vegetation.Dispute
Grasping front and middle legs; long oar-like hind legsDispute
A thin silvery bubble of air trapped against the bodyDispute
Where it turns up
Ponds and quiet areas of lakes and streams, holding on to plant stems or other objects.MDC-BACKSWIMMERSDispute
How it moves
Rows belly-up; rests tilted head-down at the surface with the abdomen tip through the film; ambushes rather than chases.Dispute
Cues this stage offers the comparison
Swims on its back, belly upwards
One pair of long, flattened, oar-like hind legs used to row
Mouthparts form a pointed beak rather than chewing jaws
Air bubble or silvery film carried under water (diving beetle / water beetle)
Confused with
Telling it from what it isn't.
BackswimmersvsWater boatmen
Right-way-up swimming, a flat back ruled by dark parallel crosslines, and scoop-shaped front feet is a boatman. Missouri says it also does not bite, and this one does.
Head-down at the surface settles nothing — a diving beetle does exactly the same. Look at the mouth: a beak is a bug, chewing jaws are a beetle. Hard wing covers meeting in a straight seam are a beetle too.
Where in the column it mattersSurface film. Hangs from the film upside down between hunts, which puts it in the one band an angler can actually see into.
Read from the record's own position notes: a backswimmer rests tilted head-down at the surface with the tip of its abdomen through the film.
Reference windows
When this group is typically available.
Typical published ranges only. Elevation, latitude, tailwater release and a given year's weather move all of these, often by weeks. This is never a statement about today.
1 reference window
Overwinter in the wateradult
JFMAMJJASOND
Overwinters as an adult. One published behavioural threshold, for a European species, has it spending most of its time submerged below about 59 °F air temperature — quoted here as an observation about one animal, not a rule for the family.
Observed: Overwintering from Wisconsin (UWM Field Station); the 59 °F threshold is Notonecta glauca in Europe. No source gives months.
No reviewed dossier names this group. That is an absence in the dossier layer rather than a finding about the animal — four dossiers exist and only one of them names any forage group at all.
Nothing in the pattern layer is mapped to this group, so no presentation family follows from it here.
Not known
What this entry cannot tell you.
11 of them. The limits are part of what was reviewed rather than a disclaimer bolted on afterwards. An entry that hid them would be claiming more than it checked.
Written by the reviewer
Declared by the reviewerThe most detailed account consulted covers a Eurasian species; its air-film duration, temperature behaviour and one-brood-a-year seasonality are not offered here as North American facts.UF-BACKSWIMMER-EENY738Evidence from: Notonecta glauca, a Eurasian speciesDispute
Declared by the reviewerMissouri lists fish among backswimmer predators, but nothing consulted rates them as important forage; one extension account also records them eating fish eggs and fry.MDC-BACKSWIMMERS, UF-BACKSWIMMER-EENY738Dispute
Declared by the reviewerBite severity differs between two sources, though both agree it takes handling.Dispute
Declared by the reviewerThe most detailed account consulted covers a Eurasian species. Its air-film duration, temperature behaviour and one-brood-a-year seasonality are not offered here as North American facts.UF-BACKSWIMMER-EENY738Evidence from: Notonecta glauca, a Eurasian speciesDispute
Declared by the reviewerMissouri lists fish among the animals that prey on backswimmers, but no source consulted rates them as important forage. The Florida extension account also records them eating fish eggs and fry.MDC-BACKSWIMMERS, UF-BACKSWIMMER-EENY738, UWM-BOATMEN-BACKSWIMMERSDispute
Declared by the reviewerNo source consulted describes whether they row with alternating or simultaneous strokes.Dispute
Sources disagreeHow badly a backswimmer bites differs by source: painful if mishandled in one state field guide, very rare and often the result of rough handling in a university extension account. Both agree it takes handling.
Sources disagreeMissouri gives adult backswimmers as usually under half an inch and Purdue lists one at half an inch; WVDEP puts the family in its 15–29 mm class, and a Florida profile of a Eurasian species gives about 16 mm.
Read off the record
Nobody typed these. They are fields that are empty, said out loud rather than left for you to notice from a section that simply is not there.
PatternsNo fly pattern in the pattern layer is mapped to this group. Whether anything imitates it is not answered here.
What eats itNo reviewed species dossier names this group. Some dossiers describe forage in class terms — small forage, insects, bait — and those are shown below, but a class description is not a reviewed link to this group and none is claimed.
Sources
Everything above rests on 8 published pages.
These are every page behind this entry. Where a reviewer traced a line above to the pages that carry it, that line names them itself, with where the evidence comes from when it is narrower than the whole entry. A line with no names beside it rests on this list as a whole: nobody has yet checked which page carried it, and naming one would be a mapping nobody made.
A plate shows shape. It cannot show a gill beating, a mask firing, or an animal reversing into sand — so where motion is the field mark, the entry points at motion. These are demonstrations, selected by hand and by publisher. Nothing here is a source: it changes no score, no window and no reviewed claim.
Deep Look. A notonectid rowing inverted with its oar legs, at length. The other half of the boatman comparison.
Science media · external video · title read back from the publisher 2026-09-09
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