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Montana Field Guide

Montana Field Guides

Giant Needlefly - Megaleuctra stigmata

Native Species

Global Rank: G2G3
State Rank: SNR

Agency Status


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General Description
This is a small black stonefly in the family; Leuctridae. Like most of the species in the rolled-winged family, this species hatches early in the year often when snow is still on the ground, where they can be noticed quite easily crawling around along the banks of streams.

Diagnostic Characteristics
Adult morphology: Body length is 11-13 mm; length to tip of wings is 15 mm. Head, thorax, abdomen, and appendages are dark brown. The three ocelli form a nearly unilateral triangle. The pronotum is about as wide as long, margins are light colored, and a central area is darker and has an indication of a wide, longitudinal, lighter median stripe. No gill remnants are on any body area. For more detailed description see Frison (1942).

Nymph morphology: Body length is 15 mm. General color is light brown. Cercal segments are at least 17 mm. A continuous membranous fold is present along the sides of the first 7 abdominal segments. The tenth tergite is drawn out and contains a dorsal sclerotized structure. Subanal lobes are bulbous, not fused distally, and rather hidden between the tenth tergite and tenth sternite (Jewett 1954).

Range Comments
Rangewide, the species is known from Washington, British Columbia, Alberta, Idaho (Idaho & Latah County), Montana (Lake & Missoula County). It is known from <30 EO's (most in Canada), mostly springs, seeps and small rheocrenes (NatureServe 2006). No map is available.

Observations in Montana Natural Heritage Program Database
Number of Observations: 1

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Very little information exists about the ecology of this species (Baumann, Gaufin, and Surdick 1977). Merritt and Cummins (1996) report that members of the genus Megaleuctra are found in small springs and seeps, and are trophically shredder-detritivores.

Food Habits
Merritt and Cummins (1996) report that members of this family are trophically shredder-detritivores; eating large particulate organic materials such as detritus, leaves and plants.

Reproductive Characteristics
No information is available.

Baumann, Gaufin, and Surdick (1977) describe this as a “rare species and it is reported to occur in only 2 counties in Montana.

Threats or Limiting Factors
Specific threats to MT populations of Megaleuctra stigmata have not been identified. In general, stonefly populations are affected by changes to aquatic habitat such as alteration of flow patterns, streambed substrate, thermal characteristics, and water quality. Alteration and degradation of aquatic habitat is the primary concern for MT populations.

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Citation for data on this website:
Giant Needlefly — Megaleuctra stigmata.  Montana Field Guide.  .  Retrieved on , from