Ilyobius erebus Mendes & Nascimento & Fusari & Santos & Hamada 2022, sp. nov.
Creators: name: Mendes, Gabriela Caroline
name: Nascimento, Jeane Marcelle Cavalcante Do
name: Fusari, Lívia Maria
name: Santos, Mireile Reis Dos
name: Hamada, Neusa
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Megaloptera
Sialidae
Ilyobius
Ilyobius erebus

description: Ilyobius erebus sp. nov. Mendes, Nascimento, Fusari & Hamada
(Figs 2–10)
Specimens examined. Holotype: male (pinned), with associated pupal and last instar exuviae in glycerin. Brazil, Minas Gerais State, Poços de Caldas, Morro do Ferro (21°53’33.6’’S; 46°33’04.2’’W); 16.VI.2021; N. Hamada, L.M. Fusari, J.O. da Silva, M. R. Santos, cols. (INPA).
Paratypes. Same data as holotype: two males: one pinned (INPA), one fixed in 80% alcohol (MZUSP), with pupae and exuviae of the last-instar larvae in glycerin; three females: one pinned (INPA), two fixed in alcohol 80% (one at INPA, one at MZUSP), with pupae and exuviae of the last instar larvae in glycerin; one last-instar larvae (INPA), fixed in 80% alcohol.
Diagnosis. Ilyobius erebus sp. nov. is distinguished from all other species in the genus by the following characters. Head and pronotum are almost completely blackish, covered with golden setae (Fig. 2A–D). Male sternite 9 is trifurcate, with medial projection longer than lateral ones, in caudal view (Fig. 4C, D). Gonocoxite 9 is robust and subtriangular in lateral view. Ectoproct is rounded in lateral view, with ventral margin fused to gonocoxite 11 (Fig. 4A, B). Gonocoxite 11 is L-shaped in lateral view (Fig. 4A, B), and divided into two sclerites medially connected in caudal view (Fig. 4C, D). Gonostylus 11 is pointed and projected upwards in lateral view (Fig. 4A, B). Female sternite 7 subtriangular in ventral view (Fig. 7C, D), with thumb-shaped projection on distal margin in lateral view (Fig. 7A, B). Gonocoxite 8 is reduced, located beneath sternite 7 (Fig. 7E). Gonapophysis 8 is subrectangular in shape, with anterior margin concave, posterior margin convex, and anterolateral corners falcate in ventral view (Fig. 7C, D). Mature larva head is orange-brown, with darker areas on anterior region (Fig. 8C).
Description. Male. Body length: mean = 7.17 mm (Standard deviation (SD) ± 0.391, n = 3); Forewing length: mean = 9.18 mm (SD ± 0.839, n = 3); width: mean = 2.54 mm (SD ± 0.361, n = 3); hindwing, length: mean = 8.25 mm (SD ± 1.06, n = 3); width: 2.55–3.10 mm (n = 2).
Head (Fig. 2C, D). Width (at the widest point): mean = 1.64 mm (SD± 0.086, n = 3); length: mean = 1.17 mm (SD ± 0.081, n = 3); region between the posterior margin of the eyes: mean = 1.55 mm (SD ± 0.065, n = 3).
General color blackish, except region of gena, surrounded by dark orange-brown area in lateral view (Fig. 2D); densely covered with golden setae. Scape, pedicel and flagellum blackish, with 30 flagellomeres, densely covered with black setae. Frons with a slight depression between the antennae (Fig. 2C). Posterior region with numerous muscle scars (Fig. 2C). Clypeus and labrum dark brown, densely covered with golden setae; clypeus with median concavity; maxillary and labial palpi dark brown, densely covered with golden and blackish setae (Fig. 2D).
Thorax (Fig. 2A). Pronotum blackish, rectangular; width: mean = 1.54 mm (SD ± 0.097, n = 3); length: mean = 0.75 mm (SD ± 0.063, n = 3), densely covered with golden setae. Meso- and metanotum blackish, subrectangular and densely covered with short, golden setae.
Legs. Dark brown, densely covered with golden setae; fore femur shorter than mid- and hind femur and slightly expanded. Tibial spurs short, yellow. Basitarsi of fore- and midleg short, slightly smaller than second and third tarsomeres together; longer on hind leg, slightly larger than second and third tarsomeres together. Pretarsal claws yellow.
Wings (Fig. 3A, B). Membrane translucent dark brown in alcohol and iridescent blackish in vivo, densely covered with golden setae. Veins light brown, pterostigma absent. Forewing: costal area slightly expanded on proximal 1/3 of the wing length, with nine crossveins; radial area with three crossveins; RP with two branches; M bifurcated near mid-length of wing; MA unforked; MP bifurcated near posterior wing margin; mediocubital area with three crossveins; CuA bifurcated near posterior margin; CuP not bifurcated. Intracubital area with a single crossvein. Area between A1 and A2 with a single crossvein; A2 forked before R fork. Area between A2 and A3 with a single crossvein. Hindwing: similar to forewing; costal area undilated, with nine crossveins; radial area with four crossveins; mediocubital area with a single crossvein; MP not bifurcated; anal area expanded (Fig. 3B).
Abdomen. Blackish, densely covered with golden setae.
Genitalia (Figs 4A–D; 5A–D; 6A, B). Tergite 9 sclerotized, densely setose; subtriangular with rounded margin in lateral view (Fig. 4A, B); in dorsal view, sub-rectangular; basal margin concave, distal margin convex (Fig. 5A, B). Sternite 9 trifurcate in caudal view, sparsely setose, central projection longer than lateral ones (Fig. 4C, D); in lateral view, medial projection wider medially (Fig. 4A, B); in ventral view, only medial projection is visible, the lateral ones are not visible (Fig. 5C, D). Endophalic sac membranous, eversible, with several fringed thorny setae (Fig. 6A, B). Gonocoxite 9 robust, setose; in lateral view, subtriangular with rounded apex, slightly concave in dorsal region, near the rounded apex (Fig. 4A, B). Anal tubercle membranous. Ectoprocts paired, in lateral view, rounded; dorsal margins convex, ventral margins straight, posteriorly directed, with proximal margins fused to gonocoxite 11 (Fig. 4A, B); in dorsal view, subtriangular, internal margins concave (Fig. 5A, B). Gonocoxite 11 L-shaped in lateral view, distal region pointed at apex and projected upwards, representing gonostylus 11 (Fig. 4A, B); gonocoxite 11 divided into two sclerites that are medially directed and connected by a membranous region in caudal view, setose (Fig. 4C, D); each sclerite with internal margin sinuous.
Female. Body length: mean = 10.51 mm (SD ± 0.375, n = 3); forewing length: mean = 10.76 mm (SD ± 0.189, n = 3); width: mean = 3.19 mm (SD ± 0.249, n = 3). Hindwing length: mean = 9.25 mm (SD ± 0.573, n = 3); width: mean = 3.53 mm (SD ± 0.166, n = 3).
General coloration and external morphology similar to male.
Head. Width (widest region): mean = 2.10 mm (SD ± 0.034, n = 3); length: mean = 1.51 mm (SD ± 0.134, n = 3); region between the posterior margin of the eyes: mean= 1.98 mm (SD ± 0.038, n = 3); scape, pedicel and flagellum blackish with 32 flagellomeres.
Thorax. Pronotum: width: mean = 1.98 mm (SD ± 0.046, n = 3); length: mean = 0.99 mm (SD ± 0.042, n = 3). Forewing: costal area with nine crossveins; area between M and CuA with two crossveins. Hindwing: similar to forewing; costal area with eight crossveins; MP not bifurcated.
Genitalia (Fig. 7A–E). Sternite 7 with thumb-shaped, posteriorly projected median projection in lateral view (Fig. 7A, B); in ventral view, subtriangular with posterior margin rounded, projected medially (Fig. 7C, D). Tergite 9 subtrapezoidal, in lateral view, ventral region broadly valvate; joined to upper region by junction line (Fig. 7A, B). Gonocoxite 8 reduced, represented by a small, setose sclerite in ventral view (Fig. 7E), located beneath sternite 7 (Fig. 7C, D). Gonapophysis 8 as a single straight sclerotized plate; in lateral view, subrectangular with falcate dorsal apex (Fig. 7A, B); in ventral view, subrectangular in shape, with anterior margin slightly concave and posterior margin convex, with lateral regions falcate (Fig. 7C, D). Gonocoxite 9 subretangular in lateral view, setose, posteriorly with a small gonostylus 9 at apex (Fig. 7A, B). Ectoproct setose, in lateral view, short, ovoid (Fig. 7A, B).
Mature larvae (Fig. 8A–D). Length = 10.24 mm (except caudal filament); maximum width = 2.32 mm (n =1).
Head (Fig. 8B, D). Length, from the clypeal margin to distal region of the head capsule = 2.49 mm; maximum width = 2.36 mm; subquadrate. Orange-brown in color, with darker areas on anterior region (Fig. 8C); strongly sclerotized; muscle scars on posterior half (Fig. 8C); several thin sparse setae distributed on head capsule. Clypeus wide and narrow, length = 0.24 mm; width = 1.72 mm. Antenna (Fig. 9D) 4-articulated; first antennomere longer than wide, wider than the others; second antennomere longer than others, ca. 2.5X longer than antennomere 1; antennomere 3 slender, ca. 1.5X longer than antennomere 1; antennomere 4 slender and shorter than antennomere 3, apically with short, setiform sensilla. Labrum (Fig. 9A) strongly sclerotized, subtriangular, ca. 5X wider at base than at apex; basally slightly wider than long; lateral margins concave; with thin setae sparsely distributed in dorsal view; in ventral view, with two pointed apophyses at tip. Mandible (Fig. 9C) symmetrical, slender and long, sharply pointed with minute basal tooth (difficult to see in specimens with worn mandibles), with two preapical teeth and a sharp terminal tooth, slightly serrated at base; outer margin convex, with basal, thin, long seta, and short slender seta near midlength. Maxilla (Fig. 9B), in ventral view, with cardo and stipes subtriangular; cardo ca. 1.5X longer than stipes. Lacinia hook-like, well developed. Galea cone-shaped. Palpifer subrectangular. Palpus: first palpomere wider than long, shorter than others; second palpomere longer than others, twice the length of the third; fourth palpomere cone-shaped. Labium (Fig. 9B) with submentum hexagonal in ventral view, ca. 1.1X longer than cardo; mentum subrectangular, slightly longer than wide, ca. 1.8X shorter than submentum, with lightly sclerotized areas; prementum wider than long, ca. 1.2X narrower than mentum; with well-developed membranous ligula.
Thorax (Figs 8A, 10A–C). Tergites orange, with diffuse blackish marks, especially on meso- and metanotum (Fig. 8A). Pronotum: length = 1.61 mm; maximum width = 2.39 mm; subrectangular, anterior margin slightly rounded, posterior margin straight. Legs (Fig. 10A–F): yellowish. Coxa of all legs slightly wider than long, with few setae sparsely distributed (Fig. 10A–F). Profemur ca. 3.5X longer than wide; internal margin with long, thick setae; internal surface with two rows of long setae near external margin (Fig. 10A); external surface with long, thick setae near external margin and with a row of shorter setae on the submedial region (Fig. 10B); mesofemur ca. 3X longer than wide; internal margin with long, thick setae; internal and external surface with a row of long setae near external margin; internal surface with a row of short setae near internal margin (Fig. 10C); external surface with a row of short setae on submedial region (Fig. 10D); hindfemur ca. 3.5X longer than wide; internal margin with long, thick setae; internal and external surface with a row of long, thin setae near external margin (Fig. 10E, F); external surface with a row of shorter setae on submedial region and with a row of pectinate sensillae above submedial row of setae (Fig. 10E); internal surface with a row of short setae near internal margin with a row of pectinate sensillae between the internal margin and the row of setae on the submedial region (Fig. 10F). Protibia ca. 2.6X longer than wide; mesotibia ca. 2.9X longer than wide; foretibia subequal in size to mesotibia. Tibia of all legs with few, long, thick setae on internal and external margins; with thin, long setae on external margin (Fig. 10A–F); internal margin with a long, thick seta; external surface of pro- and mesothoracic legs with a row of short, thick setae submedially (Fig. 10B, D); external and internal surface of metathoracic leg with pectinate sensillae below the submedial row of setae (Fig. 10E, F). Protarsus ca. 3.5X longer than wide; mesotarsus ca. 3.9X longer than wide; metatarsus ca. 3X longer than wide; internal and external margin of prothoracic and mesothoracic leg with thick setae; external margin with thin setae; external surface with longitudinal row of thick setae dorsally and ventrally (Fig. 10B, D); external and internal surface of metathoracic leg, with a row of short, thick setae submedially; with pectinate sensillae below the submedial row of setae (Fig. 10E, F). Tarsal claws with approximately the same width along the entire length.
Abdomen (Fig. 8A). Poorly sclerotized; light brown; abdominal gills whitish translucent.
Etymology. The specific epithet is derived from Erebus, Latin for darkness, an allusion to the coloration of this new species, the first in the genus that is almost completely dark. The name is a genitive in the fourth declension.
Distribution. Poços de Caldas municipality, Morro do Ferro, Minas Gerais State, Brazil (Fig. 1A, B).
description: Published as part of Mendes, Gabriela Caroline, Nascimento, Jeane Marcelle Cavalcante Do, Fusari, Lívia Maria, Santos, Mireile Reis Dos & Hamada, Neusa, 2022, A new species of Ilyobius Enderlein, 1910 (Megaloptera: Sialidae) from a threatened region in the Mantiqueira Mountain range (Brazil), pp. 346-364 in Zootaxa 5165 (3) on pages 349-359, DOI: 10.11646/zootaxa.5165.3.2, http://zenodo.org/record/6838312