Mayfly Species Tricorythodes fictus (Tricos)

A dark red-brown species, heavily shaded with smoky black; abdomen with dorsal markings and intersegmental rings whitish; forceps base with a moderately deep apical excavation.

Male- vertex of head quite bright red-brown; posterior ocelli whitish, black-ringed at base; eyes black; antennae tinged faintly with reddish basally, filament pale. Thorax deep red-brown; pronotum with black margins, black median line with a pale area on each side of it, heavy black shading laterad of pale area and beyond this a large patch of brown. Scutellum, except tip, lateral sutures and a V-mark anterior to it, black; tip of scutellum pale grey. Anterior to and below wing roots and around the base of middle leg are pale areas; rather extensive black markings on pleura. Prosternum largely pale, with heavy smoky shading. Ganglionic areas of thoracic sternum pale greyish outlined with black. Femora red-brown; dorsal and ventral edges black; a blackish longitudinal streak on outer surface, and extensive whitish areas on the dorsal side of this, in basal half; middle and hind femora heavily shaded with greyish black, becoming reddish brown apically. Extreme base of tibia black; a narrow pale area beyond this, remainder of segment smoky grey. Tarsi whitish, terminal joint of fore tarsus smoky brown; others faintly tinged with red-brown. Wings hyaline whitish; subcosta and radius greyish in basal two-thirds; basal costal space semi-opaque, tinged with grey; longitudinal veins of anterior half of wing dark, paler toward margin.

Reddish brown ground color of abdomen almost wholly obscured by general and extensive greyish-black shading. Intersegmental areas pale. Tergites 3-8 with median whitish areas on the posterior margins, most extensive on 8; each pale area bordered anteriorly and laterally by a black line, which then extends laterad along posterior margin to pleural fold; on median line of each tergite is a pale hyaline spot, largest on 6-8. Tergite 9 blackish except for median pale spot; 10 reddish brown with black median streak. Pleural fold pale, heavily marked with black. Sternites with pale intersegmental rings widest in median area; a mid-ventral blackish spot on each; short black lateral dashes next to pleural fold. Forceps base smoky black, with narrow whitish median streak; apical margin with a moderately deep excavation. Forceps pearl-grey; penes pale brown. Tails rather deep smoky grey at base, paler distally; basal joinings blackish.

Female with pale areas on vertex of head; more extensive areas on thorax dorsally and laterally; abdomen rather light red-brown, the blackish markings deeper in color but less widely distributed; intersegmental areas not so noticeably pale.

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

Larvae of Tricorythodes fictus were collected and reared from Honey Creek and several locations in the Hill Country of Central Texas. Larvae appear to prefer small to moderate sized streams with limestone outcrops. Small bits of limestone and other debris can often be found attached to hairs on the thorax and abdomen of this species. Mature larvae were collected during the winter and early spring months, indicating an early season emergence for this species. Tricorythodes fictus is currently known from south­central Oklahoma throughout the Hill Country of Central Texas, south to Chihuahua, Mexico (Randolph and McCafferty, 2000). Additional larval material from south­central Mexico seems to belong to this species, but cannot be determined with certainty at this time because adults are unknown.

Larvae: Body length 3.5 – 6.0 mm; caudal filaments 2.5 – 3.0 mm. General color pale yellowish-­brown with underlying gray maculation; immature larvae pale with limited gray maculation. Head: Pale yellow with limited gray maculation; compound eyes remote, widely separated; ocelli clear; antennae approximately 2 to 3 times length of head capsule. Mouthparts: Labrum (Fig. 1) 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; branched setae along anterior margin. Right mandible (Fig. 2) with outer incisors three-­lobed; inner incisor two-­lobed; prostheca and molar region as in figure 2; scattered setae on dorsal surface. Left mandible (Fig. 3) with outer incisors four-lobed, mostly fused; inner incisor two-­lobed; prostheca arising at base of inner incisor, with thicker base and more setae than on right incisor, but not appearing fused with inner incisor; molar region as in figure 3; scattered setae on dorsal surface. Hypopharynx with long, fine simple setae on anterior surface (Fig. 4); inner basal edge of superlinguae with row of setae. Maxilla (Fig. 5) with one-­segmented palp and terminal setae; apex of galea-lacinia with cluster of fused spines and row of heavy setae. Labium (Fig. 6) with moderately­ expanded mentum; numerous long, simple setae along outer margins; glossae and paraglossae subequal in length with numerous long, simple setae; edges of glossae and paraglossae jagged; notch between glossae deeper with bottom more rounded than notches between glossae and paraglossae; labial palp three­-segmented with long, simple apical setae. Thorax: Pale­ yellowish-brown, with hairs along lateral margins. Pronotum with gray maculation along margins and mid­dorsal line; long, simple setae along lateral margins and median transverse ridge. Dorsal surface of forefemur with median transverse row of long setae, inner margin with small setae anteriorly, and outer margin with row of long setae, becoming shorter apically (Fig. 7). Tarsal claws (Fig. 8) with single row of uniform, small, apically flattened denticles numbering 14 – 16 (with minute apical denticle, slightly separated from primary row, only visible at high magnification). 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 14 denticles, respectively; denticles sometimes flattened. Abdomen: Terga 2 – 9 with transverse, anterior gray maculation (much reduced in early instars); scattered hairlike setae present on terga. Dorsal lamella of gill two (operculate gill) subtriangular brownish­-yellow with areas near margins shaded grayish-­black (Fig. 9) and hairs along most of margin; 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, composed of diatoms, bacteria, fungi, and detritus.