One filament, straight back. A hellgrammite has two hooks.
First checkLook at the back end. One filament, or two hooks?
This is the confusion this set was most likely to get wrong, and it is decided at the back end. An alderfly larva finishes in a single tail filament pointing straight back. A hellgrammite finishes in a pair of hooked, leg-like grapples.Dispute
The rest agrees. An alderfly carries seven pairs of pointed filaments along the abdomen with nothing tufted at their bases; a hellgrammite carries eight pairs, most with a cottony gill tuft, and is usually much larger and much darker.MDC-ALDERFLY-LARVAE, UFIFAS-EDIS-EASTERN-DOBSONFLYDispute
Habitat usually separates them too. Look for most alderflies in the soft, quiet, silty pockets — detritus in a pond, a silt-bottomed pool in a slow river — though some live in clearer, faster streams. The fast cobble riffle is where the hellgrammite is.MDC-ALDERFLY-LARVAE, MDC-ALDERFLIES, MDC-HELLGRAMMITEDispute
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 Alderfly larva
A single tail filament pointing straight back, and no paired hooks+7
Hardened head with softer worm-like abdomen+2
Aquatic insect crawling on rock or debris+2
Argues against it
Fish-shaped forage silhouette (minnow / shiner / fry) — not an insect-5
No hardened head capsule and no legs — soft and segmented throughout-5
Moving as a school or tight bait cluster, not as a single insect-4
Terminal prolegs or hooks at the rear-4
Three tail filaments clearly visible-4
Two tail filaments clearly visible-4
Portable case or case-like structure present-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
Hard wing covers (elytra) meeting in a straight line down the back-4
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
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
Swollen rear end gripping a rock in current, body standing up and waving downstream-4
No long tail filaments visible-3
Air bubble or silvery film carried under water (diving beetle / water beetle)-3
Wings held upright (sailboat posture)-3
Wings held flat and parallel along the body-3
Winged insect at or near the surface-3
Fleshy lobes or a disc at the blunt rear end-3
Head withdrawn into the front of the body, hard to see-3
Two long antennae-2
Plate-like or feather-like abdominal gills visible-1
Gills at the thorax or leg bases-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.
Alderfly larva — Larva — the only stage in the waterdrawn
Soft, silty, detritus-littered bottoms: lake and pond margins, and silt-bottomed pools in the quieter sections of rivers and streams.Dispute
How it moves
Crawls and burrows in silt and detritus. It undulates the abdomen when it swims, but it is not an open-water animal.Dispute
Cues this stage offers the comparison
A single tail filament pointing straight back, and no paired hooks
Hardened head with softer worm-like abdomen
Aquatic insect crawling on rock or debris
no reviewed plateNo drawing yet. The adult is a bankside insect that is rarely what an observer is holding, and a plate has not been authored for it — that is a gap in this guide rather than a claim that the adult is unremarkable.Alderfly larva — Adultgap
The back end. One straight filament is an alderfly; a pair of hooked prolegs, plus cottony gill tufts along the abdomen, is a hellgrammite; hooks without the tufts is a fishfly.
Where in the column it mattersIn the substrate. In soft bottom. The larva leaves the water by crawling out at the bank rather than by rising through the column, so it never crosses the water an angler is fishing.
Read from the record's own position notes: silt-bottomed pools and quiet sections; soft detritus in lakes and ponds.
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
Larvae leave the waterlarva
JFMAMJJASOND
This is not a hatch. The larvae crawl out at the bank and pupate ashore, so the event happens on land and nothing comes off the surface. A West Virginia creek study recorded peak emergence at 52–55 °F, and at the Michigan site most larvae left the water after rain.
Observed: Sialis mohri at one Michigan lake (Intermediate Lake, Antrim County), 2015–2017. The temperature band and the hour come from other studies the paper cites (Japan, West Virginia, Alberta); across studies emergence runs from January in Texas to mid-June in Alberta.
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.
9 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 pupa is terrestrial. Alderflies crawl out of the water at night and pupate ashore, so nothing hatches off the surface — this is year-round subsurface forage, not a hatch.USFS-NRS-ALDERFLY-EMERGENCE, MDC-ALDERFLY-LARVAEDispute
Declared by the reviewerGroup level does not give the species, and emergence timing is species-dependent and happens where you will not see it.Dispute
Declared by the reviewerIt does not give the instar. Alderflies usually pass through eight to ten larval instars, up to about 25 mm.USFS-NRS-ALDERFLY-EMERGENCEDispute
Declared by the reviewerThe pupa is terrestrial. Alderflies crawl out of the water and pupate ashore in soil or rotten wood, so there is no aquatic pupal drift and nothing hatches off the surface — the value of this record is as year-round subsurface forage, not as a hatch.MDC-ALDERFLY-LARVAE, USFS-NRS-ALDERFLY-EMERGENCEDispute
Declared by the reviewerA group-level call does not give the species, and emergence timing is species-dependent and happens out of the water where an angler will not see it.Dispute
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 9 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.
Declared gap. The obvious candidates are Corydalidae, which is the hellgrammite. Pointing a Sialidae entry at a dobsonfly larva would put the wrong animal on the page that exists to separate them.
Carry it on
Take the group to the next step.
These send the class of animal and the water this record is documented in. They do not send a sighting, because this page does not have one — you have not told it what you saw.
Which fish in this kind of water are documented eating this class of forage, and how they behave when they are.
What this forage class asks of the setup — the weight it wants, and where the chain gives first.
Keep the group on the day's record, so a later entry can be compared against what you were looking at.
Found an error?
This entry was written and drawn away from your water. If something here is wrong, say so — the report is assembled in your browser and sent only if you send it.