Paraleptophlebia ontario ( McDunnough, 1926: 299 )

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 : 15-16

Paraleptophlebia ontario ( McDunnough, 1926: 299)

Leptophlebia ontario McDunnough, 1926 (original description)

Description of Nymph: Burks 1953: 92

Nymphs of P. ontario 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 lacking long, hair-like marginal setae ( Fig. 34 ), legs light brown with dark brown shading on femora forming partial bands and with dark brown marks on the basal inner edge of tibiae near joints with femora ( Figs. 29a,b , 33d ), ventral edge of femora with only a few short hair-like setae ( Fig. 25a ), abdominal sternites with diffuse brown lateral longitudinal bands with darker brown area where diffuse lateral bands meet the posterior margins of sternites ( Figs. 34 ), first segment of maxillary palp long, with apex reaching beyond outer corner of galea-lacinia and with only few setae on ventral surface ( Figs. 27a,b ), posterolateral projections on segments VIII and IX about equal in length ( Fig. 34 ), color pattern of abdominal tergites consisting of brown background with paired pale oval submedial spots at the anterior margins of tergites I–VIII and a thin pale median streak that is often margined with black ( Figs. 33a–d ) and a variably sized pale spot that often occurs medially along the posterior margins of tergites IV–IX, and abdominal gills with the clear membranous portion of gill filaments tapering symmetrically from base to the tip ( Fig. 34 ). Most characters seem consistent on nymphs from mid-development to the final instar as well as between sexes. Abdominal gills may appear to lack marginal setae or have a few short, widely spaced marginal setae. Legs are uniform light brown except for dark brown shading on femora and the dark brown mark on tibiae near joint with femora ( Figs. 29a,b ). Dark brown shading on the dorsal surface of femora is restricted to the outer half of the surface and is occasionally bisected by a longitudinal pale streak. Brown shading does not completely encircle femora and thus is described as forming incomplete bands. Evidence of residual brown shading also occurs on legs of nymphal exuviae ( Fig. 29a ). Legs also have small pale areas that occur near joints (including at the joint with claws) that break-up the uniform light brown background color of the leg segments. On some specimens these pale areas can appear to punctuate the background color of leg segments such that tibiae and tarsi may seem as if they are faintly banded. An important leg character is the dark brown mark on the inner edge of the base of tibiae ( Fig. 29b ), which is even visible on shed exuviae ( Fig. 29a ). This brown mark is clearly visible when the tibia is not folded inward against the femur, but when the base of the tibia is partially covered by the rounded apex of the femur the apparent intensity of the mark is greater because of the combined effect of the brown color of the rounded apex the femur overlapping the tibia ( Fig. 29b ). The region of brown shading on the base of the tibia is not uniform around the circumference of the segment with the outer edge only lightly pigmented or pale. Thus, it is not the same as the basal band that occurs on the tibiae of P. debilis . Femora have few widely separated long hair-like setae along their ventral edge ( Fig. 25a ), which can be difficult to view on intact legs. Abdominal sternites exhibit diffuse lateral brown bands with dark brown on each sternite where shading of each section of the lateral bands meets the posterior margins of sternites ( Fig. 34 ). Burks (1953) did not mention this feature of the abdomen in his description of the nymph of P. ontario . Reexamination of the series of specimens from Illinois: Wolf Lake, Hutchins Creek May 14-25, 1940, that Burks (1953) cited as material studied showed only extremely faint traces of lateral shading on sternite IX on two nymphs. It is likely that by the time these specimens were studied by Burks that more than 10 years of preservation in ethanol caused extensive fading. The study of nymphal exuviae of reared specimens from PA also showed only extremely faint traces of lateral band shading on sternite IX indicating that the color observed on nymphs ( Fig. 34 ) is not retained on exuviae. Moreover, this feature seems to be variably expressed with abdominal sternites on some individuals showing brown lateral bands with dark dashes and others from the same location only showing evidence of the dark lateral dashes ( Fig. 34 ). The maxillary palps on most specimens studied extended out beyond the edge of the mandible allowing a clear view of segment 1 (it is not usually necessary to slide mount this structure). Segment 1 is long with the apex clearly above the outer corner of the galea-lacinia and almost reaches the midpoint of the longest crown setae ( Figs. 27a,b ). This character by itself is not uniquely diagnostic of P. ontario , but is useful as a supplemental character after couplet- 6 in the new key. The color and patterning of abdominal tergites is distinctive among the northeastern species of Paraleptophlebia , but poorly described in the literature ( Burks 1953). Tergites have a medium brown background color that may have extensive gray overshading on their posterior half ( Figs. 33a–d ). On some specimens dark gray shading can become intense on some tergites forming very dark (almost black) w-shaped margins around paired submedian pale spots on the anterior half of tergites. In addition, pale triangular spots may occur medially on the posterior margins of tergites IV–X that may merge at their apex with the pale median streak creating a pale area below the dark w-shaped margin emphasizing its appearance. Although tergites have pale margins, they usually lack the separate paired lateral pale spots that are obvious on the tergites of P. debilis . However, this condition varies between males and females with some female nymphs having distinct pale lateral spots that merge with the pale lateral margins. Lastly, abdominal gills are all deeply forked with long delicate filaments. The clear membranous portion of each gill filament is relatively thin and tapers symmetrically from the base of the gill to the tips of each filament ( Fig. 34 ).

Paraleptophlebia ontario is an uncommon (potentially rare) species in the northeast Nearctic region with records in only 4 of the 14 states and provinces ( Table 2). Currently it has somewhat of an anomalous regional distribution with records in far western NY, central and western PA, southern QC, and central NB. Currently there is no obvious reason for the absence of records across the intervening states of ME, NH, and VT, or the province of NS. The stream systems in southern QC ( Harper & Harper 1982) and NB ( Giberson 2008), where adults of P. ontario were collected, do not seem to be regionally unique. Based on the habitat description of the QC ( Harper & Cloutier 1979, Harper & Harper 1982) and NB (Giberson person. comm.) sites, the streams appear similar to many streams of the same size that occur across the northern parts of VT, western and northern ME, and central NS. Therefore, the simplest explanation for the apparent disjunction across the northern distribution of P. ontario is lack of sampling effort at the appropriate time. Most records of P. ontario show it to be broadly distributed across parts of the midwestern and southeastern U.S. ( Randolph & McCafferty 1998; McCafferty et al. 2010; Klubertanz 2016) as well as southern ON near Lakes Erie and Ontario ( McDunnough 1926) suggesting that it is mostly a southern species that reaches its northern limit in QC and NB. Despite the bulk of records being in the southeastern and midwestern U.S., almost all of what is known about the life history of P. ontario comes from studies in Canada ( Harper & Harper 1982; Giberson 2008). Nymphs occur in second to third order channels with mineral substrates ranging from cobbles to gravel and some finer sediments. Channels where adults were collected in QC and NB were roughly mid-network in position and not high gradient with current velocities less than 0.5 m /s. These types of stream habitats are particularly susceptible to high flow runoff events that cause extensive changes in channel morphology. Such events are predicted to become more prevalent across the northeast Nearctic region as a result of climate change ( Hicke et al. 2022). Paraleptophlebia ontario is likely secure in its distribution across the majority of its southern and midwestern range, however, its future across the northeastern Nearctic region is uncertain. Currently more populations of P. ontario have been recorded in PA than any of the other northeastern states or provinces; this greater occurrence may result in a higher level of habitat security. However, if the lack of records north of PA actually reflects a high level of regional rarity (i.e., that is not the result of sampling effort) it could mean that P. ontario is vulnerable to local extirpation across this part of its range.

Figures

FIGS 34: nymphs of Paraleptophlebia ontario. ventral view of male and female nymph of P. ontario with arrow indicating traces of dark lateral dashes that occur on the posterior margins of sternites, near tip of arrow also note traces of dark shading along lateral margins that can appear as poorly developed lateral bands.

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. 28–29: mouthparts and legs of Paraleptophlebia nymphs. 28a. right maxilla of P. moerens (dorsal view), 28b. close-up of segment 1 of maxillary palp (ventral surface) of P. moerens, 29a. foreleg of P. ontario nymphal exuviae from reared specimen with residual dark brown shading visible on femur from partial apical band, arrow indicates dark brown mark at base of tibia adjacent to joint with femur, some brown shading around mark extends along the sides of tibia, but doesn’t completely encircle the leg segment, 29b. lateral view of legs of P. ontario nymph intact showing coloration, arrow indicates dark brown mark at apex of tibia adjacent to joint with femur.

FIGS. 33a–c: nymphs of Paraleptophlebia ontario. 33a. dorsal view of abdominal color pattern of male nymph from Pennsylvania, with slight dark gray shading in posterior half of tergites, 33b. dorsal view of abdominal color pattern of male nymph from Pennsylvania, USA with extensive dark gray shading in posterior half of tergites, 33c. dorsal view of abdominal color pattern of male nymph from Illinois USA, that has been preserved in ethanol for 84 years, some gray shading still evident on tergites, 33d. dorsal view of abdominal color pattern of female nymph from Pennsylvania, with slight dark gray shading in posterior half of tergites, shading often less extensive than on male nymphs.

FIGS. 25a–c: forefemora of Paraleptophlebia nymphs. 25a. close-up of ventral edge of forefemur of P. ontario showing few short, hair-like setae and stout setae, 25b. close-up of ventral edge of forefemur of P. debilis showing few short, hair-like setae and stout setae, 25c close-up of ventral edge of forefemur of P. moerens showing few short, hair-like setae and stout setae.

FIGS. 27a–c: maxillae of Paraleptophlebia nymphs. 27a. right maxilla of P. ontario (dorsal view), 27b. close-up of segment 1 of maxillary palp (ventral surface) of P. ontario, 27c. right maxilla of P. debilis (dorsal view), 27d. close-up of segment 1 of maxillary palp (ventral surface) of P. debilis.