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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Saddle-case Makers
This common name refers to only one family. Click its scientific name to learn more.
Caddisfly Family Glossosomatidae
These are often called Saddle-case Makers.
This family is one of the primitive caddisflies of the Rhyacophiloidea superfamily. However, they are not free-living like their better known cousins the Rhyacophilidae (Green Rockworm). Instead they build rounded "turtle" shaped cases that do not surround the larvae but are rather attached to the rock surface at their margins. Underneath is a sling made of secretions upon which the larvae ride, hence the common name Saddle-case Makers. There are four genera of possible interest but only one is generally recognized as important to anglers. See Glossosoma (Little Brown Short-horned Caddis) for details. The other three are so tiny that they are also called Pseudo-microcaddis.
Protoptila (Tiny Spotted Short-horned Caddis) is rarely important in trout streams and is generally found in warmer, larger water than the other two genera.
Agapetus (Tiny black Short-horned Caddis) is quite common in many northern streams.
Matrioptila is an extremely tiny southern genus.
Protoptila (Tiny Spotted Short-horned Caddis) is rarely important in trout streams and is generally found in warmer, larger water than the other two genera.
Agapetus (Tiny black Short-horned Caddis) is quite common in many northern streams.
Matrioptila is an extremely tiny southern genus.
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.
See 2 more specimens...
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.