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Hexagenia limbata

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Dorsal view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen appears to be of the same species as this one collected in the same spot two months earlier. The identification of both is tentative. This one suffered some physical damage before being photographed, too, so the colors aren't totally natural. I was mostly photographing it to test out some new camera setting idea, which worked really well for a couple of closeups.

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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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Stonefly Species Remenus bilobatus (Lash Springflies)

Species Range

source

Identification

Species ID from GBIFthe Global Biodiversity Information Facility

Source: Holomorphology And Systematics Of The Eastern Nearctic Stonefly Genus Remenus Ricker (Plecoptera: Perlodidae)

Diagnosis. Remenus bilobatus, with its characteristic epiproct lash is easily separated from the other Remenus species. However, the lash is rarely complete and may become broken as a result of collection, eversion, preservation, or possibly the lash is naturally broken during development or on mated individuals. Even when incomplete the lash generally still greatly exceeds the epiproct apex. The only other species of Remenus with a dorsal sclerite on the epiproct is Remenus duffieldi, but it does not greatly exceed the epiproct apex as in this species.

Males of Remenus bilobatus are further differentiated in that the epiproct is laterally flattened, the 9 th tergum has a medial glabrous division, both terga 8 and 9 have mediolateral patches of sensilla basiconica, and the basal cowl is clothed in dense golden-brown spinulae. Whereas in males of Remenus duffieldi, the epiproct is dorsoventrally flattened, tergum 9 is not divided and lacks sensilla basiconica, and the spinulae covering the basal cowl are pale.

In general, the female subgenital plate of Remenus bilobatus is broadly triangular or broadly rounded, with basolateral margins either parallel or convergent posteriorly and a basolateral crease that is nearly straight or convex posteriorly. The subgenital plate can be quite similar to the other species, but the nearly straight or convex basolateral crease is consistently different compared to the concave crease seen in Remenus daniellae sp. n., and Remenus kirchneri. Females of Remenus bilobatus differ from Remenus duffieldi by a generally shorter subgenital plate and in pronotal pigmentation. The pronotum of Remenus bilobatus is brown with pale rugosities, whereas in Remenus duffieldi, it is pale with brown rugosities. We still agree with Kondratieff & Nelson (1995) who asserted that females of Remenus should not routinely be identified in the absence of male specimens.

Mature larvae of Remenus bilobatus can be separated from Remenus kirchneri and Remenus duffieldi by the presence of long setae on the basal cercal segments. However, this character is shared by Remenus daniellae sp. n. which is sympatric in several locations. Rearing of larvae is still the best hope for species level identification.

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.

Description from GBIFthe Global Biodiversity Information Facility

Source: Holomorphology And Systematics Of The Eastern Nearctic Stonefly Genus Remenus Ricker (Plecoptera: Perlodidae)

(Figs. 3 – 18, 20 – 40) http: // lsid. speciesfile. org / urn: lsid: Plecoptera. speciesfile. org: TaxonName: 608Source: Holomorphology And Systematics Of The Eastern Nearctic Stonefly Genus Remenus Ricker (Plecoptera: Perlodidae)

Male. (Fig 20). Macropterous; forewing length 10.0 – 11.0 mm (n = 10) (Fig. 21). Body length 8.1 – 10.6 mm (n = 10). General body color yellow-gold with light brown markings. Dorsum of head typical of genus (Fig. 22). Pronotum light brown, covered in regularly spaced setae, with pale, glabrous rugosities mediolaterally (Fig. 22); medial pale area widest posteriorly (Fig. 22). Abdominal terga uniformly yellow-gold (Fig. 23). Tergum 8 with mediolateral patches of <10 sensilla basiconica (Fig. 23). Tergum 9 with a medial glabrous division that extends anteriorly ¾ tergum length and mediolateral patches of ~ 20 sensilla basiconica (Fig. 23). Hemitergal lobes short, separated from 10 th tergum, with long trichoid sensilla and> 20 sensilla basiconica on each lobe (Figs. 23 – 26). Epiproct length ~ 300 – 320 µm ; width ~ 80 – 84 µm (n = 3); epiproct flattened laterally (Figs. 23, 26), with a ventral keel (Figs. 24, 27 – 28), and a mediodorsal sclerite that is broadest basally and greatly exceeds the epiproct apex terminating in a thread-like lash (Figs. 23, 26 - 27); complete lash length ~ 830 µm (n = 1); keel widest at mid-length (Fig. 26), covered in dense, hair-like spinulae (Fig. 28). Paragenital plates broadly triangular (Figs. 23 – 24, 26). Basal cowl clothed in dense golden-brown spinulae (Figs. 23 – 24).

Female. Macropterous; forewing length 9.8 – 12.0 mm (n = 10). Body length 8.8 – 11.1 mm (n = 10). Body coloration and morphology similar to male. Sternum 8 with variable subgenital plate extending ~ ½ over sternum 9, or to the posterior margin of sternum 9; subgenital plate moderately sclerotized, broadly triangular (Fig. 29) or broadly rounded (Fig. 30); with regularly spaced setae; posterolateral margins convex; basolateral margins either parallel or convergent posteriorly; basolateral crease nearly straight or convex posteriorly, extending ~ 1/3 length anteriorly into sternum 8 (Figs. 29 – 30).

Ovum. Shape typical of genus (Figs. 31 – 34). Length 439 – 440 µm; width 348 – 361 µm (n = 3).

Larva. (Fig. 35). Body length 9.0 – 10.4 mm, (n = 5). Head (Fig. 36), lacinia (Fig. 37), mandibles (Fig. 38), and pronotum (Fig. 36) typical of genus. Mature male larva with an elongate terminal process with a constriction at the basal 1/3; apical 2/3 thin and tapered (Fig. 39). Mature larva with paired medial and lateral spots on the abdominal terga. Basal cercal segments with whorls of both long and short setae (Fig. 40).

Start a Discussion of Remenus bilobatus