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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

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 Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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 Epeorus punctatus

Caucci and Nastasi reported in Hatches II that they found fishable hatches of this species, and that they are "slightly smaller and darker" than Epeorus vitreus.

Where & when

Time of year : Late June through July

The USGS only shows this species reported from a single county in upstate New York, but I assume it is at least a little bit more widespread.

In 1 record from GBIF, this species has been collected at elevation of 3986 ft.

Species Range


Source: Contribution to the taxonomy of Eastern North American Epeorus Eaton (Ephemeroptera: Heptageniidae)

Diagnosis: Larvae of Epeorus punctatus are differentiated from those of all other North American Epeorus species by the following combination of characters: the lamellae of the first pair of gills are not enlarged anteriorly; the apex of the hind femur has a bluntly pointed projection; the setae of the subdorsal row on each femur are simple; and the dorsal and ventral posterolateral spines of the abdomen are subequal in length. Epeorus punctatus appears to be most similar to Epeorus subpallidus. Male adults of Epeorus punctatus are most reliably differentiated from those of Epeorus subpallidus by the absence of lateral spines on the penes. Additionally, the abdominal terga of Epeorus subpallidus are darkened only medially on the posterior margin and there are not any dark markings laterally; in Epeorus punctatus there is a dark line along the entire posterior margin of each abdominal tergum that broadens laterally and there are also small, dark lateral maculae. The thorax of Epeorus subpallidus is a pale yellowish brown whereas that of Epeorus punctatus is a dark chestnut brown. Larvae of Epeorus punctatus are smaller in size than those of Epeorus subpallidus; the femoral flanges of the former are bluntly pointed rather than sharply pointed; and the pair of small pronotal protuberances of Epeorus subpallidus are absent in Epeorus punctatus.

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

Described in Needham et al (1935) as Iron punctatus
Body length: 8 mm
Wing length: 8 mm

Allied to I. humeralis (now a synonym of Epeorus vitreus), but smaller, with blackish-brown head and thorax; no lateral spines on penes. Eyes smaller than in humeralis, not contiguous. Head and thorax deep blackish brown. An area posterior to scutellum, lateral edges of mesonotum, and pleural sutures, yellowish. Mesosternum shaded with ochreous between legs. Legs yellowish white; femora with dark median and apical marks; apex of fore tibia black. Wings hyaline; venation pale; humeral cross vein black-tinged. Abdominal segments 2-7 pale hyaline, posterior margins of tergites “very faintly and narrowly edged with blackish” (McD).; a distinct row of blackish dots at mid-dorsal line on posterior margin of each tergite; “in certain lights faint traces of a lateral row of small darkish spots is evident” (McD.). Segments 8-10 opaque; tergites with brown shading. Tails and forceps pale whitish. Genitalia shown in fig. 106. Very similar to I. humeralis; distinguished by the smaller eyes, paler tergites, darker thorax and lack of lateral spines near apex of penes.

Start a Discussion of Epeorus punctatus


  • Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Epeorus punctatus

Species Range
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