Cloeodes Traver 1938

Genus Cloeodes Traver 1938

(Figs 1–146)

Genus Cloeodes: Salles, Gattoliatt & Sartori 2016: 100 (diagnosis for larvae and imagoes). Type species: Cloeodes maculipes Traver 1938.

Systematic position. According to the phylogenetic classification of Baetidae (Kluge & Novikova 2011), Cloeodes belongs to the following subsequently subordinated taxa: Tetramerotarsata Kluge 1997> Liberevenata Kluge 1997> Turbanoculata Kluge 1997> Anteropatellata Kluge 1997> Baetovectata Kluge & Novikova 2011. Patella-tibial suture is typical for Anteropatellata [see discussion of apomorphy (1)]. Gonovectes have structure typical for Baetovectata (Figs 36, 88, 91, 118).

Autapomorphies of Cloeodes. (1) On larval tibia, proximal arched row of fine setae is very regular, with setal sockets contiguous; this setal row is short and disconnected with patella-tibial suture (Fig. 16; Kluge 1991: Fig. 3:6; Salles et al. 2015: Figs 7 d, 9d, 12a, 14a, 16a, 18a, 20a, 22a, 24a, 26a, 28a; Salles et al. 2016: 6F). The species of doubtful position incus Waltz & McCafferty 1987a [Bernerius] has this character (Waltz & McCafferty 1987a: Fig. 11).

In Cloeodes patella-tibial suture retains usual shape, being not shifted distally (Fig. 16), and is equally developed on all legs on larva (Figs 21–23, 60–62, 102) and on all legs of female subimago and imago; it is absent only on fore legs of male subimago and imago. These features are initial for Anteropatellata and different from Centroptella and Chopralla, whose patella-tibial suture on larval middle and hind legs is greatly shifted distally, and on fore legs is absent in all stages.

Proximal arched row of fine setae is developed on larval tibia in some other taxa, being a plesiomorphy (Salles et al. 2016); it can be poorly expressed (e.g., in Indocloeon — Kluge 2012a: Fig. 15), or dense and regular, but with spaces between setae sockets and stretched distally up to beginning of the patella-tibial suture (e.g., in Cloeoninae—Kluge & Novikova 1992: Figs 1–2). In Centroptella and Chopralla it is also regular and spaced, being greatly elongated.

(2) On larval abdominal sternum, transverse row of fine setae is very regular, with setal sockets contiguous (Fig. 20: Waltz & McCafferty 1987a: Fig. 5; 1987b: Fig. 44; Salles et al. 2015: 10E–F). Setae of these rows are long and simple (not furcate). Pair of these setal rows is present on each of abdominal sterna II–VI (Salles et al. 2016). On sternum II these rows can be either well-developed, or vestigial, consisting of few (3–2) setae, which sometimes are situated not close together. Waltz & McCafferty (1987a) wrote about incus [Bernerius], that its sterna have «long, fine setae randomly scattered over surface, without tufts of setae», that was a reason for placing it to a separate genus Bernerius Waltz & McCafferty 1987a.

Transverse rows of long setae on the same places of abdominal sterna are present also in Centroptella and Chopralla, but their setal sockets are separated, and all setae are bifurcate. Presence of such spaced rows of bifurcate setae is not a reliable apomorphy, because the same rows are present in some non-related taxa, for example in selected Oriental species of Procloeon Bengtsson 1915 (Salles et al. 2016 and own observation). Unlike this, rows of non-bifurcate setae with contiguous sockets is not found in taxa other than Cloeodes.

Setae forming transverse rows on sterna, are very delicate and colorless; under light microscope, their structure is well visible only if prepare a dry slide of empty cuticle (molting exuviae can be used for this purpose).

Other characters of Cloeodes.

Eyes of female imago enlarged and projected above head surface (Figs 27, 83; Waltz & McCafferty 1987b: Fig. 17). The same in some other taxa.

Subimaginal tarsi bear pointed microlepides at least on apical (initial 5th) tarsomere; previous tarsomeres are either also covered by pointed microlepides, or covered mainly by blunt microlepides (as in Kluge & Novikova 2014: Figs 11–17) (Table 1). In this respect Cloeodes differs from Baetofemorata and some other taxa, whose tarsi are entirely covered by blunt microlepides.

In last larval instar, developing subimaginal gonostyli are folded under larval cuticle in « Nigrobaetis -type» pose, with 2nd segment bent by convexity medially, and 3rd segment directed caudally (Figs 33, 86, 89, 116, 136). This pose is the most usual for the plesiomorphon Baetovectata-non-Baetofemorata, to which Cloeodes belongs.

Variable characters of Cloeodes. MARGINAL INTERCALARIES OF FORE WING. At least in male, fore wing has double marginal intercalaries—i. e. two intercalaries per space between veins (Figs 32, 110). In female, marginal intercalaries are either double as in male, or secondarily single. Among species examined, females of Cloeodes vibratorius sp. n. and C. auwe Salles et al. 2004 have marginal intercalaries double, as in male (Fig. 26). Females of Cloeodes redactus Waltz & McCafferty 1987, C. nigrohumeris sp. n., C. superior Kluge 1991 and C. inferior Kluge 1991 have marginal intercalaries less developed than in male: between some veins only one intercalary is present, between others intercalaries are absent; sometimes marginal intercalaries are absent on the whole wing. In the cases, when there is one marginal intercalary in a space between veins, this intercalary locates not in the middle of the space, but either anteriad, or posteriad of the middle (Figs 85, 114; Kluge 1991: Fig. 13). Such eccentric single marginal intercalaries are secondary ones, i. e. originating from double intercalaries characteristic for Baetovectata. In contrast to them, the primary single marginal intercalaries, which are initially characteristic for Liberevenata, are located at the middle of each space. In this respect Cloeodes differs from the Afrotropical taxon Potamocloeon Gillies 1990 (= Maliqua Lugo-Ortiz & McCafferty 1997), which some authors united with Cloeodes (Jacobus & McCafferty & Gattolliat 2006): in contrast to Cloeodes, whose marginal intercalaries are either double or eccentric, Potamocloeon has one marginal intercalary in the middle of space, that is characteristic for baetid taxa other than Baetovectata.

HIND WING. In various species of Cloeodes, hind wings are either developed in both sexes, or absent in both sexes; in the last case larva has no vestiges of hind protoptera (Figs. 22, 61, 102). All species of Cloeodes known from North and Central America, have no hind wings. Among South American species reliably attributed to Cloeodes (i.e., with known larval characters), hind wings are absent in C. redactus Waltz & McCafferty 1987b, C. auwe Salles & Batista (in Salles et al.) 2004, C. barituensis Nieto & Richard 2008, C. maracatu Lima et al. (in Massariol et al.) 2013, C. spaceki Queiroz et al. (in Massariol et al.) 2013 and two new species described here— C. vibratorius sp. n. and C. nigrohumeris sp. n. (key for larvae of these two-winged species is given below). Other known South American species have hind wings (Salles et al. 2015).

MAXILLA. General shape of maxilla is uniform in all Cloeodes: it has short biting edge and thick distal dentiseta adjacent to canines (Fig. 7); however, shape of the distal dentiseta varies among species: in most species its apex is bent toward canines (Figs 8, 142) (that can be called « Baetis -type»), while in C. auwe, C. spaceki and C. nigrohumeris sp. n. distal dentiseta is bent in the same direction as canines (Fig. 109) (that can be called « Cloeon - type»).

RESPIRATORY MOVEMENTS OF LARVA. In most Baetidae ability/inability for respiratory movements by tergalii is a character of high-level taxa; particularly, all representatives of the large world-wide taxon Baetungulata Kluge & Novikova 2011 are unable for respiratory vibrations by tergalii (that can be called « Baetis -type») and all representatives of the large Arctogean taxon Cloeonini (sensu Kluge 2016) are able for rhythmical respiratory movements by tergalii (that can be called « Cloeon -type»). Ability/inability for respiratory movements can be revealed if place alive larva to stagnant water with low oxygen concentration. In Cloeodes this character is speciesspecific: among species examined, C. superior, C. inferior and C. redactus do not make respiratory movements, while tergalii of C. nigrohumeris sp. n. are able to make fast synchronous vibrations with small amplitude. Larva of C. vibratorius sp. n. makes unusual respiratory movements by the whole body and usually does not vibrate by tergalii, but is able to do it.

STRUCTURE OF TERGALII. In the two-winged species of Cloeodes examined by me, tergalii have speciesspecific shape, but uniform structure: ribs are present only on proximal parts of costal and anal margins; ribs are smooth, without denticles; distal margin of tergalius is free of rib and slightly notched, with small seta in each notch (Figs 37–57, 119–132). Among fore-winged species, tergalii are more diverse: in some species tergalius, besides marginal ribs, has a median rib running close to median trachea (Salles et al. 2015). Similar median rib is present in all examined species of Centroptella and Chopralla (unpublished data).

APODEME OF LARVAL PARAPROCTS. Pair of paraprocts represent a ventral sclerite (sternite) of abdominal segment X, which is the last segment of the insect body (Kluge 2004). Paired ventral longitudinal muscles, being serially homologous in abdominal segments I–IX, stretch from anterior margin of each sternite to anterior margin of the next sternite; in abdominal segment IX these muscles stretch from anterior margin of sternite IX to anterior margins of paraprocts; pair of these muscles convergent posteriorly and are attached on a common unpaired base of paraprocts. This intersegmental ventral muscle is figured on longitudinal section in male imaginal genitals (Kluge (2012b: Fig. 18); paired anterior insertions of these muscles on anterior margin of sternite IX of male imago are shown here on Figs 35, 88, 91 and 118 as “m.IX-X”. In larva, pair of these muscles is also attached to a common unpaired base of paraprocts. In most mayflies paraprocts have no significant apodeme at place of this muscle attachment, but in some species of Cloeodes such apodeme is present. Among species examined, C. vibratorius has a long, thick, pigmented apodeme (Figs 15, 19), C. redactus has thin and flexible apodeme (Fig. 67), and C. nigrohumeris lacks significant apodeme (Fig. 107). Possibly, strong development of this apodeme in C. vibratorius is connected with its peculiar abdominal respiratory movements. Similar apodemes are figured on paraprocts of some four-winged species of Cloeodes (Salles et al. 2015: Figs 22 f, 24f and some others).