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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Lateral view of a Clostoeca disjuncta (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington
This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
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 Caudatella heterocaudata

This species is quite rare, but Fred Arbona in Mayflies, the Angler, and the Trout says creates "fair" hatches in places.

Where & when

Time of year : July and August

In 1 record from GBIF, this species has been collected at elevation of 1699 ft.

Species Range

Hatching behavior

Time of day : Midday

Nymph biology

Current speed: Fast

Identification

To determine whether a specimen of Caudatella belongs to Caudatella heterocaudata, use the Key to Species of Caudatella Nymphs.

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.

Body length: 6–7 mm
Wing length: 6.5–7.5 mm

Eyes reddish-brown. Thorax olivebrown, yellowish patch anterior to the base of the wing, containing a black line which descends to the coxa of the foreleg; lateral sutures marked with black; legs pale olive-brown; fore femora and tibia with black markings; wings hyaline with pale veins and cross veins. Abdominal terga olive-brown, anterior half of each of the first four segments with broad black bands, bands on posterior segments reduced to large semicircular dorsal patches; sterna pale olive-brown with ~midventral and sublateral longitudinal dark brown stripes as in fig. 7. Caudal filaments brown, lateral cerci 20%-30% as long as terminal filament. Penes with a shallow median apical depression as in fig. 3.

Body length: 6–7 mm
Wing length: 6.5–7.5 mm

Similar to male except for usual sexual differences.

Body length: 7–8 mm

Cerci 2-3 mm long; terminal filament 10-12 mm long. Head brown with pale markings, roughened but without occipital tubercles; antennae brown ; maxillary palpi three-segmented as in fig. 12. Thorax brown; legs brown, femora with a few marginal spines and a distinct row of marginal hairs, tibiae and tarsi with a distinct row of marginal hairs (fig. 15), tarsal claws with three to seven denticles. Abdominal terga olive-brown; anterior half of each of the first four segments with broad black bands, bands on posterior segments reduced to large semicircular dorsal patches; each tergum with a series of lateral black patches; paired dorsal abdominal tubercles on segments 1-9 or 2-9 as in figs. 1 and 23; sterna pale olive-brown with median and paired sublateral longitudinal dark brown stripes as in fig. 7. Caudal filaments light brown, darker at the joinings; lateral cerci 20% to 30% as long as terminal filament.

Specimens of the Mayfly Species Caudatella heterocaudata

1 Male Dun
1 Female Dun

Start a Discussion of Caudatella heterocaudata

References

  • Allen, R.K., and Edmunds, George F. Jr. 1961. A Revision of the Genus Ephemerella (Ephemeroptera: Ephemerellidae) II. The Subgenus Caudatella. Annals of the Entomological Society of America 54: 603-612.
  • Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.

Mayfly Species Caudatella heterocaudata

Species Range
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