Mayfly Species Tricorythodes cobbi (Tricos)

Source: Life stage descriptions, taxonomic notes, and new records for the mayfly family Leptohyphidae (Ephemeroptera)

Larva: Body length 3.5 – 5.0 mm; caudal filaments 2 – 3.5 mm. General color pale reddish­brown; immature larvae much paler with limited gray maculation. Head: Reddish­brown; compound eyes remote, widely separated; ocelli clear. Antennae approximately 2 – 3 x length of head capsule. Mouthparts: Labrum (Fig. 10) dorsally with long, fine simple setae along lateral margin; row of short, branched setae recessed from anterior margin; ventrally with vertical row of simple, fine setae near mid­line; short row of branched setae along anterior margin. Right mandible (Fig. 11) strongly curved towards base, with outer incisors three­-lobed; inner incisor two-­lobed; prostheca and molar region as in figure 11; scattered setae on dorsal surface. Left mandible (Fig. 12) with outer incisors four-­lobed, fused for most of their distance; inner incisors two-­lobed; prostheca visible at base of inner incisor, not appearing fused to side of incisor; base of inner incisor closely associated with base of outer incisor, appearing as a single unit. Hypopharynx with long, fine simple setae on anterior margin (Fig. 13); inner basal edge of superlinguae with row of setae. Maxilla (Fig. 14) with elongate two-­segmented palp, segment two with faint annuli (visible only at 400 x magnification) and elongate apical seta that is broad at base and tapers to sharp point; apex of galea­-lacinia with pair of large fused spines and row of smaller separate spines. Labium (Fig. 15) with moderately­ expanded mentum with regularly ­spaced long, simple setae along outer margins; glossae and paraglossae subequal with numerous long, simple setae and smooth outer margins; notch between glossae equal in depth and appearance to notch between glossae and paraglossae; labial palp three-­segmented with long, simple setae. Thorax: Reddish­brown, with hairs and setae scattered along lateral margins and median transverse ridge. Dorsal surface of forefemur with median transverse row of heavy setae, inner margin with numerous, small setae, and outer margin with few, long setae, setae shorter apically (Fig. 16). Tarsal claws (Fig. 17) with single row of uniform, small, pointed denticles numbering 10 – 12, apical denticle separated from previous denticles. Mesofemora­ and metafemora with few, scattered setae on dorsal surface not forming a distinct row as in forefemur; mesoclaws­ and metaclaws with approximately 10 and 12 denticles, respectively; denticles sometimes flattened. Abdomen: Terga 2 – 9 pale to dark reddish­brown; scattered hair-like setae present on terga. Dorsal lamella of gill 2 (operculate gill) subtriangular with more or less uniform black shading (Fig. 18); outer margin with longitudinal ridge and scattered small setae along edge of ridge; inner apex with numerous, long setae. Cerci with row of setae at each annulation. Body frequently covered by thick periphyton biofilm and detritus.