Paraleptophlebia volitans ( McDunnough, 1924: 95 )

Burian, Steven K., 2024, Nymphs of the Northeastern Nearctic Species of Neoleptophlebia Kluge, 1997 and Paraleptophlebia Lestage, 1917 (Ephemeroptera: Leptophlebiidae), Zootaxa 5521 (1), pp. 1-65 : 34-37

Paraleptophlebia volitans ( McDunnough, 1924: 95)

Leptophlebia volitans McDunnough, 1924 (original description)

Description of Nymph: Ide 1930: 204; Gordon 1933: 123

Nymphs of P. volitans can be recognized from other members of the northeast Paraleptophlebia that have posterolateral projections of abdominal segments VIII and IX (as in Figs. 3b–d ) by the deeply forked abdominal gills with long, hair-like marginal setae ( Fig. 17 ), legs uniform light brown with brown bands ( Figs. 18a,b ), the ventral edge of femora with many long, hair-like setae (Figs. 19a,b), the first segment of maxillary palp short, with apex not reaching beyond outer corner of galea-lacinia and with patch of 10–13 sharp setae on the ventral surface (Figs. 21a,b), the posterolateral projections on segment IX distinctly larger than those on tergite VIII ( Fig. 3c ), and the color pattern of abdominal tergites as in Fig. 17 with paired pale submedian spots and a single pale median spot with variable dark brown marks on tergites I–IX. The largest areas of dark brown are on tergites I, II, V, and VIII ( Fig. 17 ), and abdominal gills have the membranous portion of gill filaments either clear or stained brown ( Fig. 17 ). Most characters seem consistent on nymphs from mid-development to the final instar. The long marginal setae along the edges of the abdominal gills ( Fig. 17 ) are widely spaced and usually clearly visible, but occasionally setae may be pressed against the surface of the gill filaments, making them difficult to observe (low-angle illumination is useful in viewing these setae). Legs are uniform light brown or yellow brown with darker brown bands ( Figs. 18a,b ); bands on femora occur near the apices of the segments, whereas, those of the tibiae and tarsi occur near the bases of the respective segments. A small pale area also occurs between the brown bands on the tibiae and tarsi and their respective joints, as well as on the apices the femora. On some individuals brown bands on the femora can be diffuse. The ventral edge of forefemora has many long, hair-like setae, especially near the base (Figs. 19a,b). Long setae parallel the row of stout, sharp setae along the ventral edge of femora and on most specimens stop at the end of this row of stout setae. The ventral edge of mid and hind femora usually have fewer long, hair-like setae compared to the forefemora. The tibiae and tarsi of all legs have outer edge fringes of many hair-like setae that are shorter than occur on the femora. Longer setae on the outer edges of tibiae and tarsi, combined with rows of thicker, spine-like setae on their inner edges contributes to generally “hairy” appearance of the legs (Fig. 19b). Tarsal claws have distinct denticles that increase in size from base to the midpoint of claws. In addition to the long hair-like setae on the legs, both right and left mandibles have long setae along their outer edges and on their ventral surface (Figs. 20a,b). Segment 1 of the maxillary palp is short with its apex just reaching the tip of the outer corner of the galea-lacinia (Fig. 21a) and its ventral surface with a distinct patch of 10–13 sharp setae (Fig. 21b). Although the length of segment 1 of the maxillary palp can be determined without removing the maxilla from a specimen, however, to view the patch of setae usually requires slide mounting the maxilla to view it at high magnification. The posterolateral projections on segment IX are distinctly larger than those on tergite VIII ( Fig. 3c ) and this character seems to be consistently expressed even on early instar nymphs. The color pattern of abdominal tergites usually is expressed as in Fig. 17 with paired pale submedian spots on the anterior margins of tergites and a single pale median spot or median streak on the posterior margin of tergites and with variable amount of dark brown marks. The color pattern shown in Fig. 17 represents the most ornate condition of dark and light spots on abdominal tergites observed among specimens studied. The least ornate condition is one where most dark brown marks are reduced or absent on tergites III, IV, VI, VII, and IX with some dark brown remaining on tergites I, II, V, and VIII. On some specimens reduced dark brown marks are only visible on tergites V, VI, and VIII. The amount of dark shading on tergites also seems to be more pronounced on female nymphs ( Fig. 17 is a female nymph) compared to male nymphs. On male nymphs, dark brown marks may be restricted to tergites VII and VIII, with tergites I–VI being mostly uniform brown except for dark shading along the posterior margins. Both male and female nymphs have small dark brown marks near the lateral margins of tergites anterior to gill insertions. Dark brown shading on abdominal tergites (in both sexes) is not retained on shed nymphal exuviae. Abdominal tergites of early instar nymphs may have a lighter yellow brown background color and dark brown shading medially and along the posterior margins of tergites I–VIII. The variability of dark shading on abdominal tergites seems quite high across the range of this species with specimens from Florida clearly within the range of pigmentation of specimens from ME. Abdominal gills also vary in the extent of pigmentation. Within a single population, gill membranes can range from clear without any dark shading to almost opaque brown ( Fig. 17 ). Membranes of abdominal gills also taper symmetrically from base to tip without any distinct change in width over the outer portion of each filament.

Nymphs of P. volitans are common throughout most of the northeast Nearctic region with records in 10 of the 14 states and provinces ( Table 2). Only NH, VT, NL-I, and NL-Lab lack records. The absence of records for NH and VT is likely the result of sampling effort, but the lack of records from NL-I and NL-Lab may reflect actual absences. The presence of P. volitans on Martha’s Vineyard ( Whitmore 2008), MA and on PE suggest that dispersal over water is possible. There are no published records of P. volitans from any area north of southern QC, which suggests that this may be the latitudinal limit of its continental range. Most records of P. volitans are from the southeastern U.S. ( McCafferty et al. 2010) with only a few records from the upper midwestern U.S. ( Burks 1953; Lager et al. 1982; Randolph & McCafferty 1998) and none further west than the Big Thicket area of eastern Texas ( Baumgardner et al. 1997; Wiersema 1998). This indicates that the southeastern U.S. likely represents the core of the continental range of P. volitans . In this part of its range, P. volitans is widespread and likely secure with regards to the potential effects of climate change on stream habitats. In the northeastern portion of its range P. volitans is common in streams ranging from small first order tributaries to large fourth (or>) order rivers. Nymphs of P. volitans seem able to tolerate a wide range of flow regimes and water quality conditions occurring in streams draining bogs and those used by Atlantic Salmon for spawning ( Burian & Gibbs 1991). Thus, based on its current widespread northeastern distribution, which is indicative of its wide habitat tolerances and perhaps dispersal ability, P. volitans is expected to be secure where it now occurs with regards to the predicted effects of climate change on regional hydrology ( Hicke et al. 2022).

Figures

FIGS. 1–4: gills and abdominal tergites VIII–X of Neoleptophlebia and Paraleptophlebia nymphs. 1. N. adoptiva gill 4, 2. P. praepedita gill 4, 3a. N. assimilis tergites VIII–X, 3b P. praepedita tergites VIII–X, 3c. P. volitans tergites VIII–X, 3d. P. moerens tergites VIII–X, 4a. N. adoptiva tergites VIII–X, 4b. P. guttata tergites VIII–X.

FIGS. 17–18: legs, and gills of Paraleptophlebia volitans. 17. dorsal view of abdominal gills with arrow indicating long, hairlike setae along edges of gill filaments, 18a. view of all legs showing presence of distinct bands, 18b close-up of foreleg (dorsal view) showing bands on each leg segment.