Erotesis schachti Malicky 1982

Ruiz-García, Antonio, Lara-Rodríguez, Andrés, Garzón, Andrés & Zamora-Muñoz, Carmen, 2022, Morphological description and DNA-based association of the last instar larva of Erotesis schachti Malicky 1982 (Trichoptera: Leptoceridae), an endemic of the Iberian Peninsula, Zootaxa 5219 (6), pp. 583-592 : 585

Erotesis schachti Malicky 1982 —last instar larva

Body length: 7–8 mm (n = 5).

Head ( Figs 1–4 ). Head width: 0.55–0.58 mm, (n = 5). Head capsule elongate, distally slightly narrower and uniformly dark brown in colour, except pale ring around each eye, with complete set of primary setae; darker muscle attachment spots visible on parietalia and on posterior third of cephalic capsule, including both sides of coronal suture ( Fig. 1 ). As in all final instar larvae of Leptoceridae , subocular ecdysial lines present on parietalia ( Fig. 2 ), but in this case with dorsal branch running sinuously from foramen occipitale on each side of head to lateral section of parietalia under each eye and visible posteriorly in dorsal view ( Figs 1 and 2 , red arrows). Frontoclypeus dark brown in colour, without distinct constriction at mid-length ( Fig. 1 ). Antennae near distal parietal borders, very long, slightly thicker apically, each with single apical seta ( Fig. 1 , black arrow). Labrum slightly notched apically with four pairs of setae on dorsal surface. Mandibles stout, not elongate and with two cutting edges, one dorsal and one ventral, and three apical teeth ( Fig. 3 ). Ventral apotome dark brown, subrectangular with rounded corners, slightly narrower in posterior 2/3 ( Fig. 4 ).

Thorax ( Figs 5 , 6, 8 ). Pronotum covered by two light brown sclerites, each with muscle attachment spots in its posterior half, with 27–30 long black setae on each sclerite ( Figs 5 , 8 ). Mesonotum covered by two large sclerites light brown in colour with several brown muscle attachment spots arranged in V-shape with 7 or 8 long black setae on each sclerite ( Fig. 5 ). Metanotum completely unsclerotized; metanotal setal areas sa2 and sa3 each with single seta only ( Fig. 5 , red arrows); setal area sa1 without setae. Prosternum and mesosternum without setae and metasternum with one seta on each side ( Fig. 6 , red arrows).

Legs ( Figs 7, 8 ) brown, with numerous setae. Foreleg femora short and wide ( Fig. 7 ); foretrochantins elongate, subrectangular and each with single seta ( Fig. 8 , red arrow). Tarsal claws of midlegs and hind legs evenly curved and each with prominent basal seta ( Fig. 7 ). Hind legs much longer than others, each tibia and tarsus having constriction and pale band at midlength ( Fig. 7 , red arrows), without fringes of long setae.

Abdomen ( Figs 9–13 ) white in colour and cylindrical. Gills absent; lateral fringes extending on each side from beginning of abdominal segment III to end of segment VIII ( Fig. 9 , red arrows). Abdominal segment I with one dorsal and two lateral protuberances ( Fig. 9 , black arrows); dorsal setal areas sa1 and sa3 not developed and without setae, dorsal setal areas sa2 with single seta on each side ( Fig. 5 , red circle); lateral sclerite on each side without strongly sclerotized dark posterior process; sclerite may range from pale tan to grey in colour; each lateral sclerite with one seta ( Fig. 10 , red arrow). Abdominal tergite IX well sclerotized, brown, bearing 6 long and 4 short terminal setae; only one dorsolateral seta on each side ( Fig. 11 , red arrows). Anal prolegs each with large lateral sclerite and strongly sclerotized anal claw with two small accessory hooks ( Fig. 12 ); each proleg with five strong black setae apically ( Figs 11, 13 ). Anal pads each with areas of dense fine and soft long setae laterally and rows of spinules medially, without tooth-edged plates or rows of strong, posteriorly directed spines ( Fig. 13 ).

Case ( Fig. 14 ). Length: 8–10 mm. Larval case composed of plant fragments such as roots and pieces of leaves arranged in two helices at least in some sections of case, one on right and one on left, tracing a zig-zag line on ventral side and another on dorsal side. In other sections of case, fragments aligned parallel or randomly. Some cases with few small mineral particles. Posterior end open, without membrane.

DNA analysis. The analysis of the barcode region of an adult of E. schachti from Garganta de la Cierva ( Spain) (GenBank accession number: OP364029 ) and two previously unknown larvae collected in the same locality showed a genetic distance of 0.00% and 0.15% ( Table 1 ). These values fit well within the intraspecific variability of mtCOI usually observed in caddisflies (Pauls et al. 2009, 2010; Previšić et al. 2009, 2014; Graf et al. 2015). Moreover, the uncorrected p-distances based on the mtCOI gene of these three individuals, a specimen of E. schachti from Portugal, and an E. baltica specimen from Finland ( Table 1 ) are in line with interspecific distances commonly reported in Leptoceridae ( Kučinić et al. 2020) . Thus, the data enable confident association of the larva and the adult of E. schachti . Furthermore, the association of larvae and adults is based not only on comparisons of sequences from these specimens as Zhou (2007) and Zhou et al. (2007) recommended, but also by their co-occurrence at the same locality.

Figures

FIGURES 1–5. Larva of Erotesis schachti Malicky 1982: (1) head capsule, dorsal; antennal apical seta, black arrow; dorsal branch of ecdysial line, red arrow; (2) head capsule, right lateral; dorsal branch of ecdysial line, red arrow; (3) left mandible, ventral; (4) head capsule, ventral; (5) head, thorax, abdominal segment I, dorsal; single seta on each of metanotal setal areas sa2 and sa3, red arrows; single seta on each dorsal setal area sa2 of abdominal segment I, red circle). All figures scale: 1 mm, except (3) scale: 0.5 mm.

FIGURES 6–10. Larva of Erotesis schachti Malicky 1982: (6) thorax, ventral; metanotal setae, red arrows; (7) left legs, posterior/lateral face, left lateral; pale band on tibia and tarsus of hind leg, red arrows; (8) head, prothorax, legs, left lateral; foretrochantin, red arrow; (9) habitus, left lateral; start and end of left lateral fringe, red arrows; dorsal and left lateral protuberances of abdominal segment I, black arrows; (10) metathorax, abdominal segments I and II, right lateral; right lateral protuberance with sclerite and one seta, red arrow. All figures scale: 1 mm.

FIGURES 11–14. Larva of Erotesis schachti Malicky 1982: (11) last abdominal segments, dorsal; dorsolateral setae on abdominal segment IX, red arrows; (12) last abdominal segments, right lateral; (13) tip of abdomen, ventral; (14) larval cases. All figures scale: 1 mm.