Caenis, Stephens, 1836

Nascimento, Stênio R. S., Rodrigues, Jackson A. O., Ale-Rocha, Rosaly & Lima, Lucas R. C., 2022, New species and records of Caenidae Newman, 1853 (Insecta: Ephemeroptera) from Northeastern Brazil, Zootaxa 5133 (1), pp. 110-122 : 119-120

Male imagos of Caenis from Brazil (adapted from Domínguez et al. 2006)

1. Apex of the forceps sharp and sclerotized................................................................. 2

- Apex of the forceps rounded........................................................................... 5

2(1). Forceps narrowing gradually toward the apex.............................................................. 3

- Forceps sharpening abruptly at the apex................................................................... 4

3(2). Surface of the forceps without setae with 3 subapical denticles; lobes of the penis fused, without vestige of a dividing groove ( Da-Silva, 1993: Fig. 4 ).................................................................... Caenis cuniana

- Forceps generally with small tubercles and setae on outer basal margin; forceps 7.3–9.5 times longer than width at the middle; apophyses strongly developed, wide and long ( Molineri et al. 2011: Figs 3 , 5 , 6A–F )................... C. teipunensis

4(2). Forceps approximately six times longer than width at half length; about six setae present on ventral surface ( Malzacher, 1986: Figs 5B, C , 11)............................................................................ C. candelata

- Forceps approximately 9-11 times longer than width at half length, approximately 15-20 setae present on ventral surface ( Malzacher, 1986: Figs 5A , 10).................................................................. C. fittkaui

5(1). Finger-like median process present in abdominal tergum II; fore leg twice as long as hind leg or longer; forceps and sclerites of the genitalia strongly colored........................................................................... 6

- Abdominal tergum II without median projections (but lateral projections may be present); fore leg at most 1.8 times the length of hind leg; forceps and sclerites of the genitalia nearly uncolored)............................................. 7

6(5). Lateral filaments of abdominal segments relatively short; lobes of penis short and laterally rounded; apophyses of the styliger sclerite long and thin, somewhat distanced from the base of the forceps ( Malzacher, 2001: Figs 7A–E)...... C. plaumanni

- Central sclerite of styliger elongated; apophyses of styliger sclerite broad and short; penis whitish with rounded lateral lobes ( Molineri & Malzacher, 2007: Figs 96–98).......................................................... C. uruzu

7(5). Lobes of the penis totally fused, without a median groove.................................................... 8

- Groove separating the lobes of the penis visible............................................................ 9

8(7). Forceps somewhat curved toward median line; without trichomes or minute spines at apex; posterior margin of styliger plate more or less straight; penis rounded and narrow at the base ( Pereira & Da-Silva, 1990: Fig. 2 )................ C. cigana

- Forceps curved toward median line, covered with trichomes with 2–3 minute spines at apex; posterior margin of styliger plate short convex; penis square-shaped, not narrow at base.................................. Caenis marataoan sp. nov.

9(7). Penis with laterally protruding lobes.................................................................... 10

- Lobes of penis very short and not or only slightl y protruding................................................ 13

10(9). Posterior margin of styliger plate straight or rounded....................................................... 11

- Posterior margin of styliger plate subtriangular............................................................ 12

11(10). Fore margin of the styliger sclerite convex; apophyses of styliger sclerite bent inwards ( Malzacher, 2001: Figs 9A–I).................................................................................................. C. tenella

- Fore margin of the styliger sclerite straight; apophyses of styliger sclerite pointed and straight ( Lima et al. 2015b: Figs 1C, D )........................................................................................ C. gaucha

12(10). Apical margin of penis convex; apophyses of the styliger sclerite bent inwardly, fore margin of the styliger sclerite concave ( Malzacher, 1990: Figs 1A, B )............................................................... C. pflugfelderi

- Apical margin of penis straight; apophyses of the styliger sclerite pointed and straight, fore margin of the styliger sclerite straight ( Alba-Tercedor & Mosquera, 1999: Figs 1 , 4 )............................................... C. chamie

13(9). Lobes of the penis very short and swollen at base; styliger plate usually covering the penis; prosternal triangle narrow and triangular, usually closed toward apex ( Malzacher, 1986: Figs 13A, 16, 18A, B).......................... C. sigillata

- Lobes of the penis relatively long; styliger plate not covering penis; prosternal triangle broad and usually open toward apex .................................................................................................. 14

14(13). Prosternal triangle very broad and open anteriorly; apex of genital forceps rounded with margins ornamented with small wartlike bumps; basal dilation of the antennal bristle about 1.5 times the length of the pedicel ( Malzacher, 1986: Figs 12E, 13C, 17, 18C)............................................................................... C. quatipuruica

- Prosternal triangle tapered and open anteriorly; apex of forceps without ornamented margins; basal dilation of the antennal bristle shorter than the length of the pedicel ( Malzacher, 1986: Figs 12C, 13B, 15, 18D–F).................... C. reissi

Figures

FIGURE 1. Distributional map with records of Brasilocaenis irmleri, B. elidioi, Caenis chamie, C. fittkaui, and Caenis marataoan sp. nov. A, Map of South America indicating previous records; B, Map of Piauí State, Brazil with new distributional records.

FIGURE 2. Caenis marataoan sp. nov. male imago: A, habitus, dorsal view; B, habitus, lateral view; C, habitus, ventral view; D, detail of thorax (ventral view); E, detail of abdomen (dorsal view). (Scale: Figs 1A–E = 0.5 mm).

FIGURE 3. Caenis marataoan sp. nov. male imago, genitalia: A, ventral view; B–E, variations in forceps. Abbreviations: f = forceps; p = penis; sp = styliger plate; a = apophysis; cs = central sclerite. (Scale: Fig. 2A = 0.1 mm; Figs 2B–E = 0.05 mm).

FIGURE 4. Caenis marataoan sp. nov. female imago:A, habitus, dorsal view; B, habitus, lateral view; C, habitus, ventral view. (Scale: Figs 3A–C = 0.5 mm).

FIGURE 6. Male imagos, body dorsal view and genitalia ventral view: A–B, Brasilocaenis irmleri; C–D, B. elidioi; E–F, Caenis chamie; G–H, C. fittkaui. (Scale: Figs 5A, C, E, F = 1 mm; Figs 5B, D, F, H = 0.2 mm).

FIGURE. 5. Caenis marataoan sp. nov. egg: A, general view; B, detail of micropyle; C, detail of polar cap. Abbreviations: pc = polar cap; c = chorion; mc = micropyle; sg = sperm guide. (Scale: Fig. 4A = 20 µm; Figs 4B, C = 10 µm).