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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
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.

Dorsal view of a Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Larva from the Yakima River in Washington
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.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Species Apobaetis lakota

Species Range

Identification

Source: Redescription of Apobaetis lakota McCafferty, 2000 (Ephemeroptera: Baetidae) and description of two new species from Brazil

Diagnosis (modified from Nieto, 2006). Larva. 1) labrum rectangular, distal margin without shallow medial emargination; medial area of distal margin with three sockets of setae on dorsal surface (Fig. 1 A); 2) maxillary palp long, more than 2.0 × the length of galea-lacinia, segment I with the same length as galea-lacinia (Fig. 1 D); 3) lingua subcircular with one medial lobe (Fig. 1 E); 4) glossa distally rounded (Fig. 1 F); 5) inner projection of labial palp segment II rounded and distally directed, segment III triangular (Fig. 1 F); 6) tarsal claws 1.3 × the length of tarsus, without row of denticles (Fig. 1 H).

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Source: Redescription of Apobaetis lakota McCafferty, 2000 (Ephemeroptera: Baetidae) and description of two new species from Brazil

Redescription. Larva. Body: 5.0 mm; cercus approximately 2.0 mm. Head. Frons and antenna not observed on slide. Labrum (Fig. 1 A): rectangular, broader than long; distal margin without shallow medial emargination and medial lobe; distolateral area and distal margin with robust setae; medial area of distal margin with three sockets of setae (setae broken) on dorsal surface; ventral surface with one row of thin setae on medial area of distal margin and one row of long thin setae near distolateral margin. Left mandible (Fig. 1 B): outer and inner sets of incisors with 4 and 3 denticles, respectively; prostheca robust, bifid at apex, inner margin frayed at middle; margin between prostheca and mola concave, with frayed lobe close to subtriangular process; tuft of robust setae at base of mola present; subtriangular process wide; denticles of mola not constricted; lateral margin convex. Right mandible (Fig. 1 C): out-er and inner sets of incisors with 3 each; prostheca slender, bifurcated at apex; margin between prostheca and mola concave; tuft of setae at base of mola absent; denticles of mola constricted (as illustrated in Cruz et al. 2018); lateral margin convex. Maxilla (Fig. 1 D): maxillary palp long, more than 2.0 × the length of galea-lacinia; segment I with the same length as galea-lacinia, segment II without distal constriction and truncated; maxillary palp with scarce, thin, simple setae scattered over surface. Hypopharynx (Fig. 1 E): lingua subcircular and longer than superlingua, with one medial lobe and without distal tuft of setae; superlingua not expanded, with short, thin, simple setae scattered over distal margin. Labium (Fig. 1 F): glossa narrowing slightly distally with apex rounded, longer than paraglossa; dorsal surface with one arc of setae on distal half, from inner to outer margin; ventral surface covered with thin setae. Paraglossa curved inward; dorsal surface with three robust setae on apex and one longitudinal row of four robust setae near inner margin; outer margin with one longitudinal row of six robust setae; ventral surface with one longitudinal row of nine robust setae in the middle, outer margin with one row of 12 robust setae. Labial palp with segment I approximately 1.0 × the length of segments II and III combined; inner projection of segment II rounded and distally directed, outer margin of projection covered with thin, long, simple setae; outer margin of segment II covered with thin, long setae; ventral surface of segment II with one row of thin, long setae near outer margin, one row of thin long setae near inner margin of projection; segment III triangular, covered with thin, long, simple setae on outer margin, dorsal surface with one row of six robust setae, outer margin concave. Thorax. Fore and mid legs not found. Hind leg. Femur: with one row of 22 short blunt setae on dorsal margin (Fig. 1 G); apex with two short blunt setae; ventral margin with one row of 11 short robust setae. Tibia: ventrally with one row of eight short robust setae. Patella-tibial suture from dorsal to ventral margin. Tarsus: ventrally with one row of ten short robust setae. Tarsal claws 1.3 × the length of tarsus, row of denticles absent (Fig. 1 H). Abdomen: Terga and sterna not found. Paraproct (Fig. 7 in McCafferty 2000) with one row of seven marginal spines, posterolateral extension without spines (not observed on slide). Gill, cerci and paracercus not found.


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Mayfly Species Apobaetis lakota

Species Range
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