Camelobaetidius mexicanus (Traver & Edmunds, 1968)

(Figs. 7; 58–66)

Dactylobaetis mexicanus Traver & Edmunds, 1968: 662; Allen & Chao, 1978: 304. Camelobaetidius mexicanus; McCafferty & Waltz, 1990: 777; McCafferty & Provonsha, 1993: 67; McCafferty et al. 2004: 206; Meyer et al. 2008: 136.

Diagnose. Nymph: 1) Labrum narrowly rounded anteriorly (Fig. 58); 2) segment II of labial palp with distomedial projection rounded and large (Fig. 63); 3) thoracic gill absent at the base of coxae; 4) tarsal claws with six denticles, first denticle distinctly longer than others (Fig. 64 a); 5) posterior margin of terga without spines.

Description. Nymph. Length of body: 2.3 mm; length of antennae: 1.5 mm; length of cerci: broken; length of terminal filament: broken; tibia I: 0.6 mm; tibia II: 0.6 mm; tibia III: 0.6 mm.

Head (Figs. 7). Brown. Antennae brown. Lateral branch of epicranial suture straight.

Labrum (Fig. 58). Narrowly rounded anteriorly, broader than long. Length about 0.7× maximum width; lateral margin with long, fine and bifid setae; anterolateral and anterior margin with long, fine, bifid and pectinate setae. Dorsally with four fine, simple setae scattered over basal area; dorsolateral arc of setae with 1 + 8 long, fine and apically pointed setae.

Left mandible (Fig. 59). Prostheca robust, apically denticulate. Margin between prostheca and mola without spine-like setae; subtriangular process narrow. Basal half without setae.

Right mandible (Fig. 60). Prostheca slender, apically with longitudinal row of denticles; margin between prostheca and mola straight, with three spine-like setae; setae at apex of mola present. Basal half with four simple setae.

Hypopharynx (Fig. 61). Lingua little shorter than superlingua; apex broadly pointed, with tuft of short, fine, simple setae. Superlingua not expanded, with fine, simple setae scattered over lateral and distal margin; apex truncated obliquely.

Maxilla (Fig. 62). Inner dorsal row of setae with two denti-setae, apical denti-seta at the same orientation of canines. Medial protuberance of galea with 1 + 2 long, fine, simple setae. Maxillary palp 1.1× length of galealacinia.

Labium (Fig. 63). Glossa shorter than paraglossa; inner margin with nine spine-like setae increasing in length distally; apex with two long, spine-like setae; outer margin with five long, spine-like setae; ventral surface with three, fine, simple setae. Paraglossa sub-rectangular, curved inward; apex with two rows of long, fine, setae; ventral surface bare; dorsal surface with five robust, simple setae near apex. Labial palp segment II with distomedial projection rounded and large; dorsally with a row of five fine, spine-like setae; segment III conical, length 0.7× width, scattered with spine-like setae.

Thorax (Figs. 7). Brown. Hind wing pad present. Thoracic gill absent at the base of coxae. Femur brown. Tibia I 0.9× length of femur I; tarsi I 0.6× length of femur. Tibia II 0.9× length of femur II; tarsi II 0.5× length of femur II. Tibia III 0.9× length of femur III; tarsi III about 0.5× length of femur III.

Forefemur (Fig. 64). Length about 2.9× maximum width; dorsally with row of c.a. 40 long, spine-like setae; posterior surface with seven short, spine-like setae near inner margin; ventrally with two short, spine-like setae. Foretibia. Ventrally with 18 short, spine-like setae; anterior surface with nine fine, simple setae near dorsal margin; patella-tibial suture present, 0.5× length of tibia. Foretarsi. Ventrally with 13 spine-like setae, and one long, fine, simple setae near apex. Tarsal claws (Fig. 64 a) with six denticles, first denticle distinctly longer than others. Mid femur. Length about 2.9× maximum width; dorsally with row of 40 long, spine-like setae. Hind femur. Length about 2.8× maximum width; dorsally with row of c.a. 30 long, spine-like setae.

Abdomen (Figs. 7). Brown. Terga without creased surface, smooth; posterior margin of tergum IV without spines. Gill oval. Gills IV (Fig. 65) light brown; margins with narrow spines intercalating short, fine, simple setae; tracheae unpigmented. Gill IV 1.7× length of segment V; gill VII 1.1× length of segment VIII. Paraproct (Fig. 66). With two spines near inner margin; surface without shagreened area; postero-lateral extension with pointed and rounded marginal spines.

Distribution. MEXICO (Traver & Edmunds, 1968); UNITED STATES (Allen & Chao, 1978); GUATEMALA (McCafferty et al. 2004); NICARAGUA (Meyer et al. 2008).

Comments. Camelobaetidius mexicanus is possibly related to C. warreni (Traver & Edmunds, 1968) and C. maidu Jacobus & McCafferty, 2005. These species share the segment II of labial palp with a distomedial projection rounded and large (Fig. 63), similar number of denticles on tarsal claws and the terminal filament as long as cerci. Camelobaetidius mexicanus is distinguished from both species by the absence of thoracic gill at the base of forecoxae.

Examined material. Paratype: One nymph (mounted on slides, medium Euparal), MEXICO, Tamaulipas, Rio Guayalejo, 22.xii.1939; Berner, L. leg. (FAMU).

Additional material: Three nymphs (mounted on slides, medium Euparal), GUATEMALA, Dept. Alta Verapaz, Rio Cahobón, San Julian, 14.vii.2002, 15°19’09’’N / 90°19’06”S, Baumgardner, D.E. Leg (UFRR).