CLADOENDESIS OF EPHEMEROPTERA

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z 

Autapomorphies of Platybaetis.

(1) Glossae and paraglossae, besides usual long pointed setae, have stout, blunt setae: apex of each glossa has 2 very thick, short, stout, blunt setae; apex of each paraglossa has a row of about 7 long, stout, blunt setae [Müller-Liebenau, 1980: Fig. 5e].

(2) Larva is adapted for crawling and feeding on wet rock surfaces out of the water: head is wide and flattened (see below); prothorax has unique modification (see below); abdomen is not diminished, but, vice verse, elongate, resembling the primitive siphlonuroid type [see (3)]; tergalii are very wide and spread laterally (Kluge & Novikova 2011: Fig.177). So general shape of larva strongly differs from that of other Acentrella/fg1 (compare with (Kluge & Novikova 2011: Fig.18).

Prothorax (Kluge & Novikova 2011: Fig.186–187) has sternal area expanded laterally, so that most part of its pleura are visible from above by sides of pronotum. Coxa of fore legs are very widely separated. Trochantins (which in mayflies are present on prothorax only) are V-shape, so that each trochantin consists of two thin stripe-like sclerites (ibid.: Fig.187: tr.a and tr.p) connected under acute angle; this angle is inserted into concavity under a peculiar paired sternal flap (ibid.: Fig.187: s.f), which projects from sternum anteriorly. Membranous area, which is bordered by coxa, episternum and trochantin, is unusually enlarged and projected anteriorly, forming a peculiar paired anterior prothoracic projection (ibid.: Fig.186-187: app). Among two stripe-like sclerites, into which trochantin is divided, the anterior one (ibid.: Fig.187: tr.a) borders the medio-anterior margin of the anterior prothoracic projection, while the posterior one (ibid.: Fig.187: tr.p) forms a lever which runs in transverse direction and connects the sternal flap with coxa. Both stripe-like sclerites, which constitute trochantin, are weakly sclerotized and pale brownish. The rest sternal area, including the anterior prothoracic projections and the anterior sternal flaps, is membranous, soft and colorless. Each anterior sternal projection is thick, soft and has roundish-cone shape; most part of its surface is membranous and colorless.

Head capsule is widened and flattened, so that its hind part lies on pronotum, while its lateral parts lie on the anterior sternal projections (Kluge & Novikova 2011: Fig.177). Mouth parts, being directed ventrally, locate between the anterior sternal projections. Probably, this construction allows larva to use its mouthparts for feeding when larva lies on wet stone out of the water, being covered by a film of water, which presses its body and head to the stone. At least in the species examined, frons is not projected above clypeus (unlike all other Acentrella/fg1) and has no dense setation (unlike most other Jubabaetis/g1).

In most cases larvae of mamasae [Platybaetis] and wallacei [Platybaetis], observed in nature, were found on stones projected from the water, either just at boundary of water and air (Kluge & Novikova 2011: Fig.199), or above the water level. In the last case, larva crawls by wet stone surface, being covered by a film of water. They prefer permanently wet substrates, which are found mainly on shad sides of large stones near small waterfalls. Larva, which locates far from the water, being frightened, does not jump (unlike Mayobaetis), but runs quickly toward the water. Such running is impossible for most other mayfly larvae (including Mayobaetis) and, probably, is served by peculiar structure of prothorax and strong legs.

Besides Platybaetis, there are some other mayflies whose larvae crawl out of the water. Larvae of Neotropical Mayobaetis have usual Baetis-like appearance, but with more robust legs; they crawl by wet stones like Platybaetis; unlike Platybaetis, larvae of Mayobaetis, being frightened, do not run toward the water, but jump very far, using unusually strong abdomen. Structure of prothorax of Platybaetis is not repeated in other mayfly larvae which crawl out of the water; it is unique among mayflies and insects in general.

(3) Abdomen [initially shortened — see Acentrella/fg1 (2)] is secondarily elongate. Abdominal terga II–IX have medioanterior myo-sigilla separated from anterior margin and forming oblique maculae (Kluge & Novikova 2011: Fig.190) (that resembles the primitive condition). Sterna II–VIII, besides medioanterior and medioposterior myo-sigilla, have additional pair of myo-sigilla located behind-mediad of the medioposterior myo-sigilla (ibid.: Fig.191) (in species examined all three pairs of sternal myo-sigilla are non-colored and poorly visible). Presence of additional muscles on abdominal sterna testifies about its secondarily elongation.

Characters of Platybaetis of unclear phylogenetic status (non-unique apomorphies).

(4) Tarsus of middle and hind leg of imago and subimago has only 2 apical spines: only 2^nd and 3^rd tarsomeres are spine-bearing; 4^th tarsomere (penultimate, with stretched apical-ventral angle) lacks apical-ventral spine (Kluge & Novikova 2011: Fig.185). Fore tarsus of female also has 2 apical spines [see Jubabaetis/fg1 (2)] (see Index of characters [2.2.78.2], [2.2.83]).

(5) Imago and subimago of both species examined at rest keep their wings spread laterally (Kluge & Novikova 2011: Fig.201) (unlike all other Acentrella/fg1, which keep their wings raised up, as most mayflies); wings of both species have crossveins darkened (Kluge & Novikova 2011: Fig.198, 201). Adults of other species are unknown, so it is unclear if these characters belong to all Platybaetis, or to certain species only.