Hex Mayflies
Hexagenia limbata
The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
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This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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Animal Phylum Arthropoda (Arthropods)
Arthropods include just about everything trout eat except for minnows, worms, and leeches.
Specimens of Arthropods:
4 Male Adults
I first just assumed this was Dicosmoecus based on anglers' conventional wisdom since it's a large orange "October caddis," but Creno set me straight. I should have keyed it out. After another look under the microscope, it lacks an anepisternal wart on the mesopleuron, which rules out Dicosmoecus. The midtibiae have 2 apical spurs and 1 pre-apical spur, and from there the color pattern of the wing points to Onocosmoecus. The location then narrows the species to unicolor.
Family-level ID following Merritt, Cummins, & Berg 5th Edition:
1. Thoracic gill remnants absent
2. Arms of mesosternal Y-ridge approach posterior end of furcal pits
3. Submental gill remnants short, obscure, or absent
4. Male. Note that sternum 9 (the long, dark, last segment) appears to be the 8th if you count from the front in the ventral view, because the first segment is not easily visible ventrally.
5. Male abdominal tergum 10 not divided posteriorly; Paraprocts modified as hooks.
6. Male abdominal tergum 10 simple without notches or other prominent processes. This one was tricky, because at first glance it looks like the hooks arise from tergum 10, but in fact they're coming from the paraprocts underneath. There's a medial groove on tergum 10 that could be seen as a "notch" too, but it seems by "notch" the key is referring to a notch in the margin.
7. Abdominal sternum 8 with a conspicuous lobe and sternum 7 without such a lobe.
This leads to Isoperla.
Among Isoperla species known in Washington, most species are ruled out by different shapes of the vesicle (the rounded posterior bump on sternum 8). Isoperla pinta is ruled out by the lack of a region of stout spinules on tergum 9. The remaining options (without knowing how to properly dissect and image the aedeagus) are Isoperla fulva, Isoperla marmorata, Isoperla tilasqua, and Isoperla gravitans, the latter of which is too large. The other three are all at least slim possibilities, but several described characteristics seem to best match Isoperla fulva, which is also mentioned as the most common western Isoperla.
1. Thoracic gill remnants absent
2. Arms of mesosternal Y-ridge approach posterior end of furcal pits
3. Submental gill remnants short, obscure, or absent
4. Male. Note that sternum 9 (the long, dark, last segment) appears to be the 8th if you count from the front in the ventral view, because the first segment is not easily visible ventrally.
5. Male abdominal tergum 10 not divided posteriorly; Paraprocts modified as hooks.
6. Male abdominal tergum 10 simple without notches or other prominent processes. This one was tricky, because at first glance it looks like the hooks arise from tergum 10, but in fact they're coming from the paraprocts underneath. There's a medial groove on tergum 10 that could be seen as a "notch" too, but it seems by "notch" the key is referring to a notch in the margin.
7. Abdominal sternum 8 with a conspicuous lobe and sternum 7 without such a lobe.
This leads to Isoperla.
Among Isoperla species known in Washington, most species are ruled out by different shapes of the vesicle (the rounded posterior bump on sternum 8). Isoperla pinta is ruled out by the lack of a region of stout spinules on tergum 9. The remaining options (without knowing how to properly dissect and image the aedeagus) are Isoperla fulva, Isoperla marmorata, Isoperla tilasqua, and Isoperla gravitans, the latter of which is too large. The other three are all at least slim possibilities, but several described characteristics seem to best match Isoperla fulva, which is also mentioned as the most common western Isoperla.
5 Female Adults
I had some trouble working through the genus key for this one because I'm not great at interpreting caddis wing venation. Fortunately, figure 19.707 in An Introduction to the Aquatic Insects of North America (Fifth Edition) shows the distinctive color pattern of the striking forewings on Hydatophylax argus, which is a perfect match for the pattern as well as venation. As there are no other species in that genus in this area, I can be pretty confident in the species ID.
I keyed this specimen to Paragnetina, and range maps would seem to rule out every species of that genus except for the common Paragnetina media.
The family ID on this one was a little bit tricky. Just going by the size, shape, and color, it looks like Chloroperlidae. However, the second anal vein of the forewing is does not appear to be forked, and the apical maxillary palpal segment is close to the length of the penultimate segment, both of which rule out that family. The position of the cubitoanal crossvein relative to the anal cell in the forewing -- touching it in this case -- indicates Perlidae (and it really doesn't have the "look" of Perlidae at all), but other characteristics, such as the metathorastic sternacostal sutures and lack of gill remnants, point to Perlodidae. That's the right answer. Moving on to Perlodidae, the key characteristics in Merritt & Cummins lead straightforwarly to Isoperla, and the species key in Jewett 1959 (The Stoneflies of the Pacific Northwest) leads to Isoperla fusca.
There is one caveat: That source does suggest a May-July emergence, whereas this one was collected in mid-September.
There is one caveat: That source does suggest a May-July emergence, whereas this one was collected in mid-September.
5 Adults
I'm not fully confident in the ID on this one. I couldn't see for sure that there are two equal pads under the tarsal claws instead of three, but it seems that way. The antennae are 4-segmented, although I'm not sure if the last segment counts as a "segment" rather than a style@ or arista sticking off the third segment. It has three ocelli. The key characteristics generally point to Empididae except "Vein R4+5 usually branched." That vein certainly isn't branched in this specimen, but the key does say "usually."
The setae on the wings make it a big tricky to identify this caddisfly from the "splayed wings" view because they obscure the venation, but several of the side views provide a good look at the important forewing veins. It keys pretty confidently to Ironoquia. Based on species ranges and a photo on BugGuide seemingly of this species and some alternatives, it seems Ironoquia lyrata is by far the most likely option.
1 Pupa
This is the first fully formed caddis pupa (technically, a pharate adult) that I've collected and photographed alive and healthy. I'll put a video of this specimen online soon, too.
5 Male Duns
Identification of this one was as follows. Body 9 mm, wing 11 mm.
Both Epeorus albertae and Epeorus dulciana should have a conspicuously darkened humeral crossvein in the forewing. This one doesn't.
The foretarsal claws are dissimilar (one sharp, one blunt), which also rules out the Epeorus albertae group.
The dark macula on the forefemora rules out Epeorus deceptivus, which is also supposed to be a little bit smaller.
Both Epeorus grandis and Epeorus permagnus should be much, much larger.
Of the species known to be present in Washington, this leaves only Epeorus longimanus, which is exactly the right size. The key to male spinners in Traver (1935) describes distinctive markings that are visible (although more faintly) in this dun: “Black posterior margins of tergites do not extend laterally to pleural fold, but an oblique black line form this margin cuts across poster-lateral triangle to pleural fold.”
Both Epeorus albertae and Epeorus dulciana should have a conspicuously darkened humeral crossvein in the forewing. This one doesn't.
The foretarsal claws are dissimilar (one sharp, one blunt), which also rules out the Epeorus albertae group.
The dark macula on the forefemora rules out Epeorus deceptivus, which is also supposed to be a little bit smaller.
Both Epeorus grandis and Epeorus permagnus should be much, much larger.
Of the species known to be present in Washington, this leaves only Epeorus longimanus, which is exactly the right size. The key to male spinners in Traver (1935) describes distinctive markings that are visible (although more faintly) in this dun: “Black posterior margins of tergites do not extend laterally to pleural fold, but an oblique black line form this margin cuts across poster-lateral triangle to pleural fold.”
This dun is smaller than would normally be expected for Drunella flavilinea, but it seems to fit the physical description of that species fairly well. I wasn't sure from the dun pictures alone, so I was hoping it would molt into a spinner. It never made it out of the dun's shuck, but it did begin the process, which allowed me with great care to tease out the last couple abdominal segments of the spinner from the still tightly attached dun shuck, enabling a more confident ID based on the shape of the spinner's penes and sub-genital plate. I also collected a nymph of flavilinea in the same river on the same evening, as well as a shed exuvium that looked large enough to belong to an emerging dun.
The other possibility I considered for a while based on the dun was Drunella pelosa, which would be the right size, but the other characteristics don't fit.
The other possibility I considered for a while based on the dun was Drunella pelosa, which would be the right size, but the other characteristics don't fit.
The positive species ID on this dun comes from both the spinner that it (or possibly one other dun just like it) molted into and the overwhelming abundance of nymphs of this species in my kicknet samples from the same site.
This dun hatched in my aquarium on July 16th from an easily identified nymph collected on July 10th, and it molted into a spinner after I photographed it. The beautiful spinner form is listed as separate specimen. I forgot to photograph the dun with the ruler, but naturally his size is pretty similar to what it was as a spinner.
A few days after unexpectedly collecting a female dun of this species, but in a sad, bedraggled shape, I went back to the same pool to see if I could find more. I was able to catch this one male dun during a dusk emergence dominated by other species, and he made it home in prime shape for photos.
4 Female Duns
This female Hex dun emerged around 11 pm, one of relatively few on the water as I rushed back to the truck to beat an approaching thunderstorm. Her tails in reality were longer than shown in the picture, but they broke off.
For years after I started this website, I was eagerly hoping to find a green drake to add to the collection, but I was never in the right part of the world at the right time. It finally happened on June 1st, 2007.
I'm fairly confident calling this dun Ephemerella tibialis because it emerged from one of several similar nymphs in my bucket, which I was able to ID with quite a bit of certainty. However, it looks very different from the other duns I currently have listed, which makes me rethink their IDs.
Although there is no key to female duns, I'm calling this dun Ephemerella excrucians because I collected several mature nymphs of that species on the same trip.
5 Male Spinners
This is a tricky one to ID. The forewings seem to be on the low end of the "crossvein count" key characteristic. There are paired marginal intercalaries in the middle area of the fore wing (kind of visible in photos, verified 100 % under microscope), and the wing and its veins are pale. Keys would seem to point to Callibaetis pictus in this case, but several other characteristics including size don't fit (pictus is smaller), and this is a bit out of its range.
Although I could not find the preserved specimen to examine under my good new microscope, I'm tentatively calling it one Rhithrogena hageni, based on apparent similarity to this specimen, which I was able to positively ID.
The relative angle of the penes is a bit shallower in this specimen, but I photographed another specimen from the same collecting trip (and I think even the same swarm, although I don't recall for sure) as the other one, and it had the shallower angle seen on this specimen. I'm guessing it's just variation within the species.
The relative angle of the penes is a bit shallower in this specimen, but I photographed another specimen from the same collecting trip (and I think even the same swarm, although I don't recall for sure) as the other one, and it had the shallower angle seen on this specimen. I'm guessing it's just variation within the species.
3 Female Spinners
I'm tentatively classifying this one as Siphlonurus alternatus, because it seems to fit that species best in the old keys in Needham's Biology of Mayflies, but I'm hesitant because I can't find documentation that southwest Montana or the surrounding area is within the species' range, although they are widely distributed throughout eastern North American and western Canada.
5 Larvae
This species of Brachycentrus was extremely common in mid-September kick net samples in the Yakima canyon.
With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.
This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
I already had one of these on the site, but these giant Hydropsychidae larvae are just too photogenic to pass up.
4 Nymphs
This striking golden stonefly is the first of its species I've had the chance to photograph.
18 Streamside Pictures of Arthropods:
This Ephemerella invaria sulphur dun got stuck in its shuck trying to emerge. This isn't exactly a "natural" pose for a photograph, but it kind of shows what an emerger pattern could look like.
In this picture: Mayfly Species Ephemerella invaria (Sulphur).
These caddisflies were thick over the water in the evening on a cold, clear northwoods lake. They were in many places on the lake, all closer to the shady shore, which also was the shore most sheltered from the wind. I'm not sure which of those features attracted them.
In this picture: Caddisfly Genus Nectopsyche (White Miller).
Many beetles of this species were jumping around the rocks like popcorn on a mid-April afternoon. I'm sure they end up in the water for the trout at times.
In this picture: Insect Order Coleoptera (Beetle).
Often mayflies can be found on houses near the river. This one molted from a dun into a spinner on the outside of our kitchen window.
Any lit dwelling near the river can attract a lot of mayflies at night. A good way to determine what's hatching is to visit a gas station (or anything else with bright lights) close to the river early in the morning.
Any lit dwelling near the river can attract a lot of mayflies at night. A good way to determine what's hatching is to visit a gas station (or anything else with bright lights) close to the river early in the morning.
In this picture: Mayfly Family Baetidae (Blue-Winged Olive).
Here's an above-the-water view of a stillborn Ephemerella subvaria dun which I also photographed from below the water.
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
A thick mating swarm of Tricorythodes mayfly spinners hovers the West Branch of the Delaware near Hale Eddy one early fall morning. View the picture full-size and you'll be able to make out the wings and tails on most of those little white dots.
This was one of many such clouds visible all up and down the river. The mayflies were impressive, but the trout did not hold up their end of the bargain -- there was not a rise in sight.
This was one of many such clouds visible all up and down the river. The mayflies were impressive, but the trout did not hold up their end of the bargain -- there was not a rise in sight.
In this picture: Mayfly Genus Tricorythodes (Trico).
I saw something strange flying around near the streambank, fluttering on and off the water's surface, so I went to check it out. I didn't recognize the wing profile in flight, and it's no surprise! These two caddisflies were joined mating, and they were very reluctant to let go.
In this picture: Caddisfly Family Hydropsychidae.
Given their home on a mossy stump in the stream bed, these light orange ants probably end up in the stream from time to time.
In this picture: Insect Family Formicidae (Ant).
This is Nectopsyche albida. Elongate wing connotes female.
In this picture: Caddisfly Genus Nectopsyche (White Miller).
18 Underwater Pictures of Arthropods:
Hundreds of cased caddisfly larvae live on this log in a small brook trout stream.
In this picture: Insect Order Trichoptera (Caddisfly).
Several Baetidae nymphs line up on a rock.
In this picture: Mayfly Family Baetidae (Blue-Winged Olive).
This is my favorite underwater picture so far. It shows a bunch of Simuliidae (black fly) larvae clinging to a rock and swinging in the fast current. There are also at least four visible mayfly nymphs, probably in the family Baetidae.
In this picture: Mayfly Family Baetidae (Blue-Winged Olive) and True Fly Family Simuliidae (Black Fly).
This is a close-up underwater view of a stillborn Ephemerella subvaria (Henrickson) female dun.
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
A Brachycentrus "Apple Caddis" pupa scoots around in the surface film. Apparently it had some difficulty emerging, so I was able to slip my camera underneath it and take a picture from below.
In this picture: Caddisfly Species Brachycentrus appalachia (Apple Caddis).
This picture from below shows a stillborn Ephemerella subvaria (Hendrickson) dun drifting on the surface amidst a number of shed pupal skins from Brachycentrus caddisflies which were heavily hatching that day.
This Brachycentrus "Apple Caddis" struggled more than its kin in escaping its pupal skin, enabling me to take an underwater picture of it from directly below. This is sort of a trout's eye view, but I used the flash for the picture so the transparent shuck appears far brighter than it really is.
In this picture: Caddisfly Species Brachycentrus appalachia (Apple Caddis).
There's a large Ephemerella subvaria nymph in the top left.
There are several mayfly and stonefly nymphs clinging to this log.
In this picture: Stonefly Family Taeniopterygidae (Willowfly) and Mayfly Family Baetidae (Blue-Winged Olive).
Some large Ephemerella mayfly nymphs cling to a log. In the background, hundreds of Simuliidae black fly larvae swing in large clusters in the current.
Three big Ephemerella subvaria mayfly nymphs share a rock with some cased caddis larvae.
The white blotches on this rock are Leucotrichia caddisfly cases, and the wispy tubes are cases made by a type of midge.
This Ephemerella subvaria (Hendrickson) nymph picture is one of my favorites.
In this picture: Mayfly Species Ephemerella subvaria (Hendrickson).
Cased caddis larvae blanket this section of stream bottom.
In this picture: Insect Order Trichoptera (Caddisfly).
In this picture: Insect Order Trichoptera (Caddisfly) and Animal Class Gastropoda (Snail).
There's a stonefly nymph in the bottom right corner of this picture, but what's really interesting is those white blotches. They're pretty common in my Wisconsin home river river, stuck flat onto the rocks--lots of rocks have a speckled look as a result. They are microcaddis cases, made by larvae of the caddisfly family Hydroptilidae. These are made by larvae of the subfamily Leucotrichiinae, most likely the genus Leucotrichia. They spin little flat oval cases of silk tight and immobile against the rocks.
In this picture: Caddisfly Species Leucotrichia pictipes (Ring Horn Microcaddis).
Discussions of Arthropoda
Possible ID
1 replies
Posted by Sreyadig on Apr 11, 2021 in the species Apobaetis futilis
Last reply on Apr 11, 2021 by Taxon
In searching for nymphs in my small stream in northern Maryland, 500 yards from the PA line, I came across a 2 tailed mayfly that was not a of the Epeorus genus.
It was in a fast riffle section along with Epeorus nymphs. This was about 3/8” in overall length including tails. Darker straw coloration with dark brownish black wing cases that were pronounced in color and shape. Biggest factor was the tails. Median caudal filament was truncated, very small compared to the outer pair. Not even sure if tail/ caudal filament should be used to describe. In my books the closest thing is the Pseudocloeon futile. Which is an old taxonomic name I’m finding out.
This find seems rare in my area and experience. Hopefully I can get a photo...
It was in a fast riffle section along with Epeorus nymphs. This was about 3/8” in overall length including tails. Darker straw coloration with dark brownish black wing cases that were pronounced in color and shape. Biggest factor was the tails. Median caudal filament was truncated, very small compared to the outer pair. Not even sure if tail/ caudal filament should be used to describe. In my books the closest thing is the Pseudocloeon futile. Which is an old taxonomic name I’m finding out.
This find seems rare in my area and experience. Hopefully I can get a photo...
Yea...
Posted by Imaxfli on Oct 23, 2020 in the species Ephoron leukon
Last reply on Oct 23, 2020 by Imaxfli
Me too looking for photos or better yet, video of matching. These things seem to pop outa the water like no other ......
Trico emergers
6 replies
Posted by Bwoklink on Jul 14, 2018 in the genus Tricorythodes
Last reply on Sep 11, 2020 by Martinlf
Anyone have experience fishing Trico emergers patterns? I've had experience fishing the winged and spinner stage, but haven't heard of anyone fishing emergers during the early morning female hatch. Anyone used emerger patterns and if so would you might sharing which ones you have found effective?
PMD Spinner - Egg sack color?
20 replies
Posted by Wbranch on Jan 26, 2010 in the species Ephemerella excrucians
Last reply on Aug 18, 2020 by Troutnut
Do any of you entomologist types know the true color of the PMD spinner? Dorothea or excrucians. Where I fish in MT there are huge spinner falls, many spents are on the water in the morning and others fall again at various periods during the day. I'd like to tie some with egg sacks as I saw many in July but forgot what color they were. Thanks.
Trico Tips
50 replies
Posted by Martinlf on Jul 21, 2007 in the genus Tricorythodes
Last reply on Jul 31, 2020 by Martinlf
I'll start with a fly patterns, follow with a bit of what I think I know about Tricos (Entomologists, please offer corrections if needed), and close with a few questions.
I love designing different patterns for Tricos, partly to keep myself entertained, and partly to show the fish something new from time to time. Jason's photos and the opinions of some fussy fish have led me to tie an extra large thorax recently on all my Tricos. My old standby is a parachute tied reverse, with a high vis post over the bend of the hook, and grizzly hackle, with no tails. It's modeled on Al's Trico, which could be found on the Little Lehigh Flyshop website until Rod closed the shop. An internet search may provide images now. It's very visible and fish generally approve. My newest fly is a take off from one of Gonzo's (Lloyd Gonzales) patterns in his book Fly-fishing Pressured Water, and it also shows the influence of Al's Trico. Gonzo ties an upside down Trico on a wide gap hook using synthetic material for the wing. I tie this fly also, and it certainly does catch fish, but I recently tied a version with grizzly hackle, making an oversize thorax and palmering hackle over the thorax to create a full wing. I then clipped hackle from the top of the fly (which becomes the bottom, as this is an upside down fly) so that the fly would sit flat, upside down, on my tying table. A drop of Locktite brush-on super glue on the bare recently clipped thorax after darkening the hackle stem with black marker and the fly was done. (By the way, I put tails on this one to balance it [P.S. Later correction: this pattern doesn't need the tails. I've caught plenty fish now on a tailless version] .) It caught several fish the first time I tried it on a heavily fished stream.
I believe for some, if not most species of Tricos, males hatch at night, females in the morning, and that the spinners fall when the air temperature hits the upper 60's. This generally means that as the season goes on, spinners hit the water later and later. Sometimes by 7:00 am (or earlier) in the early summer, by 10:00 (or later) in the fall.
It's been unseasonably cool in the Northeast the past couple of days, and I would have gone out this morning but for taking my daughter to a midnight showing of The Order of the Phoenix (I just couldn't get up) but I'm wondering if the spinner fall happens later than normal on cool mid-summer mornings like today's. I hope to find out Monday, but am curious if anyone has experiences to share. Also, does anyone have an effective Trico pattern to share? I'm always looking for ideas.
I love designing different patterns for Tricos, partly to keep myself entertained, and partly to show the fish something new from time to time. Jason's photos and the opinions of some fussy fish have led me to tie an extra large thorax recently on all my Tricos. My old standby is a parachute tied reverse, with a high vis post over the bend of the hook, and grizzly hackle, with no tails. It's modeled on Al's Trico, which could be found on the Little Lehigh Flyshop website until Rod closed the shop. An internet search may provide images now. It's very visible and fish generally approve. My newest fly is a take off from one of Gonzo's (Lloyd Gonzales) patterns in his book Fly-fishing Pressured Water, and it also shows the influence of Al's Trico. Gonzo ties an upside down Trico on a wide gap hook using synthetic material for the wing. I tie this fly also, and it certainly does catch fish, but I recently tied a version with grizzly hackle, making an oversize thorax and palmering hackle over the thorax to create a full wing. I then clipped hackle from the top of the fly (which becomes the bottom, as this is an upside down fly) so that the fly would sit flat, upside down, on my tying table. A drop of Locktite brush-on super glue on the bare recently clipped thorax after darkening the hackle stem with black marker and the fly was done. (By the way, I put tails on this one to balance it [P.S. Later correction: this pattern doesn't need the tails. I've caught plenty fish now on a tailless version] .) It caught several fish the first time I tried it on a heavily fished stream.
I believe for some, if not most species of Tricos, males hatch at night, females in the morning, and that the spinners fall when the air temperature hits the upper 60's. This generally means that as the season goes on, spinners hit the water later and later. Sometimes by 7:00 am (or earlier) in the early summer, by 10:00 (or later) in the fall.
It's been unseasonably cool in the Northeast the past couple of days, and I would have gone out this morning but for taking my daughter to a midnight showing of The Order of the Phoenix (I just couldn't get up) but I'm wondering if the spinner fall happens later than normal on cool mid-summer mornings like today's. I hope to find out Monday, but am curious if anyone has experiences to share. Also, does anyone have an effective Trico pattern to share? I'm always looking for ideas.
Start a Discussion of Arthropoda
References
- Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.