The mask is the tell. The 'tails' on a damsel nymph are gills.
First checkLook at the mouth. If you can see a grasping mask, you are in Odonata.
Odonata nymphs are predators. The extendable labium — the mask — is the strongest field separator from mayfly and stonefly.
Damselfly nymphs are slender with three leaf-like caudal lamellae. Those lamellae are commonly misread as mayfly tails. Look at the shape: flattened and leaf-like, not round filaments.
Dragonfly nymphs are robust and lack those external lamellae. Adults hunt over stillwater and slow margins.
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 Damselfly / Dragonfly
Extendable grasping mouthparts (labium / mask) on an aquatic nymph+6
Three leaf-like caudal lamellae at the tail (damselfly nymph) rather than round filaments+5
Three tail filaments clearly visible+1
No long tail filaments visible+1
Winged insect at or near the surface+1
Aquatic insect crawling on rock or debris+1
Wings held flat and parallel along the body+1
Argues against it
Fish-shaped forage silhouette (minnow / shiner / fry) — not an insect-5
Portable case or case-like structure present-4
Pinched waist (ant / flying ant) with elbowed antennae-4
Hard wing covers (elytra) meeting in a straight line down the back-4
Moving as a school or tight bait cluster, not as a single insect-4
No hardened head capsule and no legs — soft and segmented throughout-4
One pair of long, flattened, oar-like hind legs used to row-4
Swims on its back, belly upwards-4
Mouthparts form a pointed beak rather than chewing jaws-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Head withdrawn into the front of the body, hard to see-4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
Fallen terrestrial insect (hopper, ant, beetle, etc.) — not an aquatic emergence-3
Hopper / grasshopper silhouette — hind legs long, body blocky, wings folded along back-3
Air bubble or silvery film carried under water (diving beetle / water beetle)-3
Swollen rear end gripping a rock in current, body standing up and waving downstream-3
Two tail filaments clearly visible-2
Hardened head with softer worm-like abdomen-2
Terminal prolegs or hooks at the rear-2
Plate-like or feather-like abdominal gills visible-2
Gills at the thorax or leg bases-2
Wings held upright (sailboat posture)-2
Wings held tent-like or inverted-V over body-2
Two long antennae-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.
Damselfly / Dragonfly — Nymphdrawn
Nymph
Size in hand8–50 mm
What you see
Extendable grasping labium
Damsel: three leaf-like caudal lamellae
Dragon: robust, no long external tails
Wing pads on mature nymphs
Where it turns up
Vegetation stems (climbers), substrate (sprawlers and burrowers).
These groups name Damselfly / Dragonfly in their own separators. If you arrived holding one of them and were not sure, this is the sentence that pointed you over.
Where in the column it mattersMid column. Climbers live in the weed, burrowers in the bottom. Damsel nymphs swim to the margin to emerge, which is the only time they cross open water.
Read from the record's own position notes: among vegetation and stems (climbers); on or in substrate (sprawlers / burrowers); adults hunting over stillwater and slow margins.
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.
2 reference windows
Nymphs available year-roundnymph
JFMAMJJASOND
Damselfly and dragonfly nymphs overwinter. They are present long before adults hunt the margins.
All day among vegetation and substrate
Adult huntingadult
JFMAMJJASOND
Adult Odonata hunt over still and slow water in the warm months. Not a current-emergence claim.
55–80 °F · Warm daylight over stillwater and slow margins
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.
6 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 reviewerBroad order only. Not a family or species call.
Declared by the reviewerNo current emergence or density claim.
Declared by the reviewerOdonata is a broad order. This record supports a damselfly/dragonfly hypothesis, not a family or species call.
Declared by the reviewerCaudal lamellae on damselfly nymphs are commonly mistaken for mayfly tails; the labium mask is the honest separator.
Declared by the reviewerThis preview does not claim a current emergence, density, or fishing pattern.
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.
Sources
Everything above rests on 3 published pages.
Attribution here is to the whole record, not to individual sentences — the carrier attaches a source set to a record and does not say which page carried which line. Naming one per claim would mean inventing a mapping nobody reviewed.
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.
Leaf Pack Network. Both nymphs swimming in the same clip: jet propulsion against three caudal lamellae sculling. That is this entry's whole internal split.
Research institute · external video · title read back from the publisher 2026-09-09
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