CLADOENDESIS OF EPHEMEROPTERA

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Autapomorphies of Isca/fg1.

(1) On maxilla apical-ventral row of pectinate setae [see Leptoiphlebia/fg1 (1)] is unusually short and consists of 3 setae; these setae are retained in Isca/fg2 and in ganeshi [Notophlebia] (Kluge 2014: Fig.6), but are lost in jobi [Notophlebia] due to its modified dilatognathan mouth apparatus (Sivaramakrishnan & Peters 1984: Fig. 15).

Among other Leptophlebiidae, reduction of these setae occurs only in some representatives with dilatognathan mouth apparatus (see Index of characters [1.1.31]): three vestigial setae are present in Dilatognathus; these setae are completely lost in Hermanellognatha. In other known leptophlebiid taxa (including dilatognathan taxa Hagenulus/fg3 and Ulmeritus/g2) there is a row of many well-developed pectinate setae.

(2) On larval fore tibia field of stout pointed bipectinate setae on inner side [see Leptophlebia/fg1 (8)] gradually turns to a longitudinal row of stout non-pectinate setae, located in distal part of ventral (posterior) side of tibia; most distal seta of this row is the most stout (Kluge 2014: Fig.2:p, Fig.52:p).

(3) While insertions of all tergalii retain their position on posterior-lateral angles of abdominal terga, terga become gradually wider and sterna become gradually narrower from abdominal segment I to abdominal segment VII, so that more posterior tergalii are inserted gradually more ventrally, than more anterior ones. In Notophlebia insertions of tergalii I–VI are gradually shifted from dorsal to lateral sides of abdomen; tergalii VII are lost (Kluge 2014: Fig.3). In Isca tergalii I are lost, and insertions of tergalii II–VII are gradually shifted from lateral to ventral sides of abdomen. Both in Notophlebia and Isca, abdomen is cylindric, with terga strongly arched and rigid. Anterior abdominal segments are somewhat shorter than posterior ones, so that tergalii insertions are somewhat brought together.

(4) Adults are shortly-moulting: both subimaginal and imaginal cuticles are developed before larval/subimaginal moult (Kluge 2014: Fig.20), and subimago moults to imago shortly after emergence. The same in some other mayfly taxa (see Index of characters [2]).

(5) Pigmented areas, which initially for Leptophlebiidae are present on cuticle of subimaginal mesonotum (Kluge 2004), are present on cuticle of imaginal mesonotum (in contrast to other Leptophlebiidae, whose cuticle of imaginal mesonotum is evenly pigmented). The pair of pigmented areas bordered by mesonotal suture are enlarged and occupy most part of medioscutum and submedioscutum, so that only three narrow colourless stripes separate them one from another and from other pigmented areas of mesonotum (Kluge 2014: Fig.11). In Isca/fg2 such pigmentation occurs both on imaginal and subimaginal cuticle. In ganeshi [Notophlebia] subimaginal cuticle is entirely colourless (Kluge 2014: Fig.12).

(6) Hind wings are completely lost; larval metanotum lacks vestiges of protoptera (Kluge 2014: Fig.3). The same in some other taxa (see Index of characters [2.2.59]). 

(7) Subimaginal legs in some degree retain size and proportions of larval legs: subimaginal fore femur is widened proximally, and hind femur widened in middle (Kluge 2014: Fig.15–17). Fore tibia and tarsus of male subimago are as short as in larva, and tarsal segments II–IV are swollen (Kluge 2014: Fig.15); after moult to imago, tibia and tarsus become several times longer (Kluge 2014: Fig.13). In most other leptophlebiids changes of male fore leg at moult from subimago to imago is not so great.

(8) On middle and hind leg, 1^st tarsal segment (initially for Ephemeroptera fused with tibia, and initially for Furcatergaliae strongly shortened) is secondarily separated from tibia and elongated (Kluge 2014: Fig.18). On inner side of leg, apex of tibia is stretched distally and retains fusion with 1^st tarsal segment; on outer side of leg, 1^st tarsal segment is well separated from tibia and proximally has a concavity, which corresponds to condylus in tibio-tarsal articulation of the larval cuticle, under which subimaginal and imaginal leg had been developed (Kluge 2014: Fig.20). Thus, number of distinct tarsal segments can be 5 (instead of 4 in most other Leptophlebiidae). 1^st, 2^nd, 3^rd and/or 4^th tarsal segments are short and can be more or less fused one with another; sometimes some of them are fused completely. Thus, total number of distinguishable tarsal segments can be either 5 (e.g., in ganeshi [Notophlebia] and purpurea [Isca]) or diminished to 4 or 3 (e.g., in serendiba [Isca]). In female, structure of fore tarsus (Kluge 2014: Fig.19) is similar to that of middle and hind tarsus. About fore tarsus of male see above (7).

(9) Penis consists of a pair of L-shaped sclerotized lobes movably connected basally (Kluge 2014: Fig.23, 26, 29). The same in some other taxa.

(10) Caudalii of subimago (which in mayflies are usually developed from proximal portions of larval caudalii) are developed from very small proximal portions of larval caudalii, so that are several times shorter than larval caudalii; caudalii of male imago have strongly elongated segments, so that are several times longer than subimaginal caudalii; caudalii of female imago in  ganeshi [Notophlebia] are subequal to subimaginal ones (in Isca/fg2 female subimago does not moult to imago). In other leptophlebiids degeneration and growth of caudalii during metamorphosis are not so great.

Characters of Isca/fg1 of unclear phylogenetic status. 

(11) In larva, patella-tibial suture (initially absent on fore legs) is lost on middle leg, being retained on hind leg only (Kluge 2014: Fig.3) (the same in Megaglena and some other taxa – see Index of characters [1.2.18]). Unlike larva, in subimago and imago patella-tibial suture is retained both on middle and hind legs (Kluge 2014: Fig.16–18) (see Index of characters [2.2.82]).

(12) Larval claw has a row of subequal denticles [see Leptophlebia/fg1 (9)] and one larger distal denticle located posteriad of this row (Kluge 2014: Fig.35). The same in some other taxa.

Plesiomorphies of Isca/fg1. Imaginal and subimaginal claws of all legs are ephemeropteroid (see Index of characters [2.2.85]).

Variable characters of Isca/fg1. In imago amphitornal margin of wing can bear setae, as in subimago of all mayflies (in serendiba [Isca], purpurea [Isca], fasciata [Isca], ganeshi [Notophlebia]), or has no setae (in janicae [Isca]) (see Index of characters [2.2.27]).

The taxon Isca/fg1 is divided into: