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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.

Artistic view of a Perlodidae (Springflies and Yellow Stones) Stonefly Nymph from the Yakima River in Washington
This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
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 Callibaetis pictus (Speckled Duns)

These dark little Speckle Wings can be locally important in the West, particularly at higher elevations. They are the smallest of the western species averaging size 18 but can run even smaller. See the Callibaetis genus Hatch page for more information.

Where & when

In 49 records from GBIF, adults of this species have mostly been collected during May (20%), April (16%), June (16%), July (14%), November (10%), August (8%), and October (8%).

In 12 records from GBIF, this species has been collected at elevations ranging from 700 to 10180 ft, with an average (median) of 3940 ft.

Species Range

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.

Male Spinner

Body length: 5-8 mm
Wing length: 5.5-8 mm

A dark brown species; cross veins of fore wing relatively few in number; marginal intercalaries paired; wing of male not pigmented.

Thoracic notum of male pitch-brown. A row of 6 to 8 or more round spots on each femur, and a few dots, which are sometimes (especially on the hind legs) confluent in part; tarsal joinings, claws, and the “last 1-3 joints” blackish or reddish brown. Wings unpigmented in male; cross veins relatively few in number; marginal intercalaries in pairs; stigmatic area slightly reddish brown in the male. Venation pitch-brown, the four main veins of the costal margin white in places, in both sexes; cross veins dark in the male, white in the female. Outer margin of female wing white here and there. No cross veins in the basal costal space, in the male;| 6-9 very faint veins in this space, in the female; 6-8 beyond the bulla, in male; 11-16 in this area, in the female, mostly simple, with no granulations.

Body greatly discolored. Abdominal tergites “closely punctulate,” sternites even more closely freckled; sternites and some portions of the tergites “rosy whitish-brown, with the punctulations dark red-brown; the remainder of the dorsum pitch brown.” Tails white or reddish white sometimes banded with grey; joinings black in the female, greyish in the male.

Described as C. doddsi

Body length 6.5 mm, wing length 6.5 mm

A brownish species; cross veins of fore wing few in number; wing of male not pigmented.

Thorax light brown; sutures pale. Wings hyaline, fore wing not pigmented in male (female not known). Cross veins of fore wing relatively few in number; intercalaries not mentioned. Hind wing likewise unpigmented; cross veins few; only one marginal intercalary. Abdominal tergites 2-6 light grey-brown, 7-10 red-brown. Sternites paler, the dark freckling becoming less dense apically to the 6th and 7th sternites; sternites 8 and 9 without freckles. Each sternite is marked with a pair of dark submedian streaks. Basal joint of forceps irregular on the inner margin, and with a slight rounded protuberance at the inner apical margin. Second joint with distinct ‘wrinkles’ near the base on the inner margin.

Described as C. pacificus

Body length 7-8 mm, wing length 7-8 mm

Male dark brown, female pale tan; cross veins of fore wing few in number; marginal intercalaries paired; wing of male barely or not at all pigmented.

Head and thorax of male blackish brown; extensive pale areas on pleura and around bases of legs; scutellum pale in middle. Head and thorax of female pale tan, with flesh-colored tinge; anterior margin of mesonotum olive brown with pale median and lateral streaks; faint brownish stippling on some portions of pleura and sternum. Scutellum yellow. Fore leg of male rather dark olive to reddish brown; femur paler at tip, with a dark pre-apical band; tarsi paler olive brown; faint traces of a row of 6 to 8 round dark dots near middle of inner surface of femur. Middle and hind legs cream-colored to pale tan; apical margins of tibiae, a wide pre-apical femoral band, and part or all of each tarsal joint, dark brown; 10 to 12 faint darker dots along middle of each femur; tibiae likewise with faint dark stippling.

Wings hyaline; cross veins few in number (18 to 20 behind first branch of radius); marginal intercalaries paired. Longitudinal veins dark brown in both sexes; in female, four main veins of costal margin with numerous pale spaces. Cross veins dark brown in male, white in female. Wing of male wholly unpigmented, or with narrow brown markings on the costa only. Wing of female irregularly and variably mottled along the costal border with pale reddish brown (see fig. 161). Costal brace pale except at base; entire costal space usually interrupted brown and white; cross veins fenestrate irregularly with hyaline. Behind the costa, several brown clouds separated by hyaline areas; a small dark area at basal fork of radius; a paler and larger cloud at and on each side of the bulla; two or more clouds beyond the bulla, the outer one at or near the wing tip. Clouds may also be present in the wing disc. Costal angulation of hind wing rather acute; cross veins few; one long intercalary.

Abdominal tergites 5, 6 and 9 of male largely creamy white, except for brown oblique submedian streaks on the anterior margins; remainder of dorsum dark red-brown, each tergite narrowly greyish white on the lateral and posterior margins. Greyish median markings on basal tergites; two creamy submedian streaks the length of tergite 10. On each segment, a dark brown mark above the pleural fold; median part of posterior margin of each tergite dark brown. Sternites paler, the basal ones greyish tinged with pale brown, the apical ones creamy; minutely and densely stippled with red-brown; a pair of curved red-brown submedian marks on each. Abdomen of female light tan flushed with pinkish; tergites 7 and 8 largely dark brown; other tergites marked with dark brown submedian triangular blotches on anterior margin, dark streaks above pleura, and a lateral oblique streak from the posterior margin; tergite 4 with more extensive submedian brown markings. Tergites stippled coarsely with red-brown in the paler areas; sternites paler than tergites, finely stippled as in the male. Forceps smoky brown. Tails dark olive brown, somewhat paler distally; joinings blackish brown; alternate joinings wider, at the base. Tails of female slightly paler.

Described as C. signatus

Body length ? mm, wing length 7-7.5 mm

A brownish species; cross veins of fore wing relatively few in number; marginal intercalaries paired; wing of male unpigmented.

Male dark brown, female pale brownish; scutellum of female pale in the middle. Legs pale, tarsi and tips of tibiae rather darker. Wings hyaline; longitudinal veins brown, cross veins hyaline, in both sexes. In wing of female, “various pale brown spots along the costal region,” but these do not form a continuous streak; “several costal dots, a basal streak, one just before the middle of wing on subcosta and radius, and three or four beyond; several other brown spots.” Wing of male unpigmented. In the type specimens, the basal costal space (female wing) is wholly pale; intercalaries of the fore wing are paired; cross veins relatively few in number. Hind wing shaped much as in C. pacificus (now a synonym of Callibaetis pictus). Abdomen of male nearly black dorsally, except for two large pale spots, “one over the penultimate segment, and the other on the third segment before the last”; venter finely dotted. Entire abdomen of female pale brownish, dotted. Tails pale, darker at the joinings.

Female Spinner

Body length: 5-8 mm
Wing length: 5.5-8 mm

Thoracic notum dark yellowish.

In the fore wing of the female, the vitta consists of a light umber-brown band in the costal and subcostal spaces and along the wing base, the brown more or less regularly alternating with hyaline white areas; just beyond the bulla, in the costal space, the brown is more extensive for a short distance. Faint and rather irregular clouds of light brown are present in the disc of the wing and along the outer margin from the edge of the vitta almost to the anal veins. Hind wing very faintly colored at extreme base; cross veins relatively few in number; usually one rather long intercalary and one or two shorter ones. Wing relatively short for its width.

Tails white or reddish white sometimes banded with grey; joinings black in the female, greyish in the male.

Described as C. pacificus

Body length 7-8 mm, wing length 7-8 mm

Male dark brown, female pale tan; cross veins of fore wing few in number; marginal intercalaries paired; wing of male barely or not at all pigmented.

Head and thorax of male blackish brown; extensive pale areas on pleura and around bases of legs; scutellum pale in middle. Head and thorax of female pale tan, with flesh-colored tinge; anterior margin of mesonotum olive brown with pale median and lateral streaks; faint brownish stippling on some portions of pleura and sternum. Scutellum yellow. Fore leg of male rather dark olive to reddish brown; femur paler at tip, with a dark pre-apical band; tarsi paler olive brown; faint traces of a row of 6 to 8 round dark dots near middle of inner surface of femur. Middle and hind legs cream-colored to pale tan; apical margins of tibiae, a wide pre-apical femoral band, and part or all of each tarsal joint, dark brown; 10 to 12 faint darker dots along middle of each femur; tibiae likewise with faint dark stippling.

Wings hyaline; cross veins few in number (18 to 20 behind first branch of radius); marginal intercalaries paired. Longitudinal veins dark brown in both sexes; in female, four main veins of costal margin with numerous pale spaces. Cross veins dark brown in male, white in female. Wing of male wholly unpigmented, or with narrow brown markings on the costa only. Wing of female irregularly and variably mottled along the costal border with pale reddish brown (see fig. 161). Costal brace pale except at base; entire costal space usually interrupted brown and white; cross veins fenestrate irregularly with hyaline. Behind the costa, several brown clouds separated by hyaline areas; a small dark area at basal fork of radius; a paler and larger cloud at and on each side of the bulla; two or more clouds beyond the bulla, the outer one at or near the wing tip. Clouds may also be present in the wing disc. Costal angulation of hind wing rather acute; cross veins few; one long intercalary.

Abdominal tergites 5, 6 and 9 of male largely creamy white, except for brown oblique submedian streaks on the anterior margins; remainder of dorsum dark red-brown, each tergite narrowly greyish white on the lateral and posterior margins. Greyish median markings on basal tergites; two creamy submedian streaks the length of tergite 10. On each segment, a dark brown mark above the pleural fold; median part of posterior margin of each tergite dark brown. Sternites paler, the basal ones greyish tinged with pale brown, the apical ones creamy; minutely and densely stippled with red-brown; a pair of curved red-brown submedian marks on each. Abdomen of female light tan flushed with pinkish; tergites 7 and 8 largely dark brown; other tergites marked with dark brown submedian triangular blotches on anterior margin, dark streaks above pleura, and a lateral oblique streak from the posterior margin; tergite 4 with more extensive submedian brown markings. Tergites stippled coarsely with red-brown in the paler areas; sternites paler than tergites, finely stippled as in the male. Forceps smoky brown. Tails dark olive brown, somewhat paler distally; joinings blackish brown; alternate joinings wider, at the base. Tails of female slightly paler.

Described as C. signatus

Body length ? mm, wing length 7-7.5 mm

A brownish species; cross veins of fore wing relatively few in number; marginal intercalaries paired; wing of male unpigmented.

Male dark brown, female pale brownish; scutellum of female pale in the middle. Legs pale, tarsi and tips of tibiae rather darker. Wings hyaline; longitudinal veins brown, cross veins hyaline, in both sexes. In wing of female, “various pale brown spots along the costal region,” but these do not form a continuous streak; “several costal dots, a basal streak, one just before the middle of wing on subcosta and radius, and three or four beyond; several other brown spots.” Wing of male unpigmented. In the type specimens, the basal costal space (female wing) is wholly pale; intercalaries of the fore wing are paired; cross veins relatively few in number. Hind wing shaped much as in C. pacificus (now a synonym of Callibaetis pictus). Abdomen of male nearly black dorsally, except for two large pale spots, “one over the penultimate segment, and the other on the third segment before the last”; venter finely dotted. Entire abdomen of female pale brownish, dotted. Tails pale, darker at the joinings.


Start a Discussion of Callibaetis pictus

References

  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Callibaetis pictus (Speckled Duns)

Taxonomy
Species Range
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