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 is a striking caddis larva with an interesting color pattern on the head. Here are some characteristics I was able to see under the microscope, but could not easily expose for a picture:
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.
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Cordulegaster Dragonfly Nymph Pictures
This is a realy big, dark dragonfly nymph. Notice how "fuzzy" it is--it's covered with small hairs that collect sediment and debris and camouflage the nymph to match its natural surroundings. The greenish cast in some of the photos of this specimen is due to strange lighting during my first night photographing things for this site.
This dragonfly was collected from the Namekagon River in Wisconsin on January 13th, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.
Discussions of this Nymph
Identification of a possible Cordulegaster Dragonfly Nymph
6 replies
Posted by IanB on May 4, 2009
Last reply on Feb 10, 2017 by Taxon
I have screened through the images on this site, and I am just having a big trouble identifying this bug I have pulled of a stone in my local river.
It is very large, maybe size 10 or slightly larger, I have found other size 14 bugs of the same shape/style (also in the picture but difficult to see) and when I came across this monster I had to know what I had found. Also, after finding very similar nymphs that are size 14, can this one actually be a dragonfly? Is it just a monster of the 'normal' brown drake? Or hendrickson hatch I have heard about on this stream?
The real issue, is that I don't see a 'normal' set of twin tails, or three tails. (again not the technical term) what I do see (on the smaller and larger bug) is almost like a large paddle, and it uses this vertical paddle to swim in the water. The head is extremely flat, and it has two small antenna (like the dragonfly photo's) and two very small barbed jaw-like protrusions below the antenna and below the eye's where the mouth would be. The back appears to have two sets of wings, (neither have fully emerged) and the eye's are very similar to the dragonfly eye's in the photo's here. Also there is almost no color at all to the fly, it is a very dark mud brown/black. It looks about the same color as all the flies I pull out of the river (except the neon green caddis). Not sure if that is just a characteristic of the river, or the bug (the color that is)
One thing that is not the same, is the abdomen (bulbous in shape in the photo's on this site) does not appear to be the same as the example I have. The bug I have has a tapered abdomen going back to this 'paddle' I mentioned earlier.
More 'macro' photo's tonight when I get home, these are crappy cell phone pics for now.
Thank you for any help!
IB
https://stillmaninteriors.sslpowered.com/Images/bug.jpg
It is very large, maybe size 10 or slightly larger, I have found other size 14 bugs of the same shape/style (also in the picture but difficult to see) and when I came across this monster I had to know what I had found. Also, after finding very similar nymphs that are size 14, can this one actually be a dragonfly? Is it just a monster of the 'normal' brown drake? Or hendrickson hatch I have heard about on this stream?
The real issue, is that I don't see a 'normal' set of twin tails, or three tails. (again not the technical term) what I do see (on the smaller and larger bug) is almost like a large paddle, and it uses this vertical paddle to swim in the water. The head is extremely flat, and it has two small antenna (like the dragonfly photo's) and two very small barbed jaw-like protrusions below the antenna and below the eye's where the mouth would be. The back appears to have two sets of wings, (neither have fully emerged) and the eye's are very similar to the dragonfly eye's in the photo's here. Also there is almost no color at all to the fly, it is a very dark mud brown/black. It looks about the same color as all the flies I pull out of the river (except the neon green caddis). Not sure if that is just a characteristic of the river, or the bug (the color that is)
One thing that is not the same, is the abdomen (bulbous in shape in the photo's on this site) does not appear to be the same as the example I have. The bug I have has a tapered abdomen going back to this 'paddle' I mentioned earlier.
More 'macro' photo's tonight when I get home, these are crappy cell phone pics for now.
Thank you for any help!
IB
https://stillmaninteriors.sslpowered.com/Images/bug.jpg
Genus
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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.
Cordulegaster Dragonfly Nymph Pictures
Collection details
Location: Namekagon River, Wisconsin
Date: January 13th, 2004
Added to site: January 25th, 2006
Author: Troutnut
Date: January 13th, 2004
Added to site: January 25th, 2006
Author: Troutnut