Camelobaetidius variabilis Wiersema, 1998

Sibaja-Araya, Fabián & Esquivel, Carlos, 2020, Redescription of four species of Camelobaetidius Demoulin, 1966 (Ephemeroptera: Baetidae) from Central and North America, Zootaxa 4758 (2), pp. 257-274 : 260-264

Camelobaetidius variabilis Wiersema, 1998

( Figures 4–5 )

Camelobaetidius variabilis Wiersema, 1998: 22 ; McCafferty & Randolph, 2000: 263; McCafferty et al. 2001: 11; McCafferty et al. 2004: 207; McCafferty, 2011b: 323; Perry & Kennedy, 2016: 1.

Diagnosis. Mature nymph. The following combination of characters can be used to diagnose C. variabilis from remaining species in the region: 1) labrum anterior margin with about 16 small, double, frayed setae; seven setae on anterodorsal arc, about 18 anterolateral setae; intermediate setae absent; ventral surface with three long setae near lateral margin; minute seta on anterior margin absent ( Fig. 4a ); 2) mandibles with seven denticles on incisors ( Fig. 4b, 4c ); 3) segment II of labial palp with rounded distomedial projection ( Figs. 5a ); 4) one short osmobranchia present at base of each forecoxa and midcoxa; 5) tarsal claws with 5–9 denticles ( Fig. 5b ); 6) posterior margin of abdominal tergum IV with rounded spines sub equal in length ( Fig. 5c ); 7) paraproct with 7–11 spines ( Fig. 5d ).

Description. Mature nymph body length: 5.6–7.0 mm; caudal filaments length 2.4–3.2 mm.

Head: Labrum ( Fig. 4a ): Broader than long; asymmetrically emarginate at apex, arc of anterodorsal setae with seven simple setae, second inner seta extending beyond margin of labrum, further than others; intermediate seta absent; numerous small setae near posterior margin; anterior margin with about 16 small, double frayed setae; lateral margin with 3 simple setae and about 15 apically frayed, long setae; ventral surface with dense arc of short, fine setae near anterior margin; three long setae near lateral margin; minute seta on anterior margin absent. Left mandible ( Fig. 4b ): incisors with seven denticles, six similar in size and a middle one very small; prostheca well-developed; no setae between prostheca and mola; numerous small, simple setae on basal region. Right mandible ( Fig. 4c ): incisor with seven denticles, six similar in size and a middle one very small; prostheca well developed; tuft of six long, simple setae between prostheca and mola; molar disk well developed; numerous small, simple setae on basal region. Hypopharynx ( Fig. 4d ): lingua about 1.8x wider than superlinguae, equal in length to superlinguae, apically pointed, hairy on dorsal and ventral surfaces; superlinguae with upper half hairy on dorsal and ventral surfaces and serrate area at middle of lateral margin. Maxillae ( Fig. 4e ): robust; galea with three apical denticles, and two apical rows of setae, some setae of one of these rows large and thick while others thin, and setae of other row shorter and curved; four setae on lacinia; palp very robust, surpassing apical denticles, segment I short, segment II thick with several marginal fine setae, segment III elongate with several marginal fine setae, longer than segment II. Labium ( Fig. 5a ): robust; glossae shorter than paraglossae; both dorsally with numerous elongate and curved setae, ventrally with several elongate and curved setae; palpi with segment I thick, as long as segments II + III, dorsal surface with numerous micropores; segment II with rounded distomedial projection, dorsal surface with several fine marginal setae, and about 4–5 short simple setae in upper half; ventral surface with several fine marginal setae; segment III short and rounded, equally developed as distomedial projection, with numerous short, robust spines on ventral surface, dorsal surface with row of short and robust setae on apex.

Thorax: Hind wing pads present; one short osmobranchia present at bases of each forecoxa and midcoxa; each claw with 5–9 denticles ( Fig. 5b ).

Abdomen: Posterior margin of tergum IV with rounded spines subequal in length and simple, fine setae surpassing length of longer spines ( Fig 5c ); paraproct with 7–11 sclerotized spines subequal in length interspersed, several micropores and simple, fine setae on dorsal surface, posterior margin with minute, rounded and triangular spines and three simple, fine setae ( Fig. 5d ).

Distribution: USA, Mexico and Guatemala ( Wiersema, 1998; McCafferty et al., 2001; McCafferty et al., 2004).

Material examined: Paratype, one mature nymph (female): USA, Texas, Williamson County, Georgetown, San Gabriel River , riffles below low water crossing at San Gabriel Park , 30°/39’/20’’N, 97°/39’/33’’W, 20.I.1997, N. A. Wiersema [ PERC] .

Figures

FIGURE 4. Camelobaetidius variabilis Wiersema 1998, nymph. a) labrum (left d. v., right v. v.), b) left mandible, c) right mandible, d) hypopharynx (left d. v., right v. v.), e) maxilla.

FIGURE 5. Camelobaetidius variabilis Wiersema 1998, nymph. a) labium (left d. v., right v. v.), b) claws, c) IV tergum spines, d) paraproct.