Ilyobius bimaculatus (Banks, 1920)

Ardila-Camacho, Adrian, Rivera-Gasperín, Sara Lariza, Martins, Caleb Califre & Contreras-Ramos, Atilano, 2021, A reappraisal of the taxonomy of Neotropical Sialidae (Insecta: Megaloptera): with the description of a new genus from Cuba, European Journal of Taxonomy 782, pp. 21-54 : 31-37

Ilyobius bimaculatus (Banks, 1920)

Figs 8–10

Protosialis bimaculata Banks, 1920: 326 .

Diagnosis

Ilyobius bimaculatus is known solely from the female holotype, which is in poor condition ( Fig. 8 ). Only few diagnostic characters were observed, which include an area just behind the antennal sockets with a semicircular brown spot. The dorsal area adjacent to the compound eyes has a brown spot, posteriorly extended, flame-shaped, with three-pronged posterior extensions. The gonocoxites 8 appear as small, paired, ovoid sclerites in lateral and ventral view. The gonapophyses 8 are observed as lateral smooth, glabrous, ovoid plates in lateral and ventral view.

Material examined

Holotype BOLIVIA • ♀; Rio Longo [Río Grande?]; alt. 750 m; Fassel leg. MCZ type 10842 .

Redescription

HEAD ( Fig. 9A–B ). Width 1.9 mm, nearly completely orange. Compound eyes dark brown, dorsal area adjacent to compound eyes with a brown spot, posteriorly extended, flame-shaped, with three-pronged posterior extensions. Antenna with scape subrectangular, enlarged, brown, covered with abundant brown setae, pedicel brown, nearly as long as wide. Area immediately behind antennal sockets with a semicircular brown spot. Frons densely setose, somewhat protuberant between antennae. Clypeus and labrum densely covered with light brown setae, anterior margin of clypeus with median concavity. Maxillary and labial palpi brown with abundant brown setae. Occiput with light orange muscle scars.

THORAX ( Fig. 9 ). Pronotum orange, rectangular, nearly 1.5 times as wide as long, densely covered with minute light yellow setae. Mesonotum wider than long, dark brown, densely covered with minute light brown setae. Metanotum similar to mesonotum, but slightly narrower. Pteropleura brown, covered with abundant setae of same color as cuticle.

LEGS. Brown, all segments densely covered with brown setae; fore femur somewhat expanded and shorter than mid- and hind femur. Tibial spurs short, brown. Basitarsus of fore- and midleg short, as long as the second and third tarsomeres together; on hind leg longer than that of fore- and midleg, as long as remainder of tarsomeres together. Pretarsal claws light amber.

WINGS ( Fig. 9C ). Forewing 12 mm long, membrane semitranslucent, smoky, densely setose. Venation light brown, densely covered with fine setae of same color as cuticle. Costal field slightly expanded on ⅓ of wing length, with nine crossveins; pterostigma absent. A single subcostal crossvein. Radial space with three crossveins, RP with two branches, basal one forked near posterior wing margin. Radiomedial space with three crossveins, M forked near mid-length of wing, MA unforked, MP forked near posterior wing margin; intramedial space with two crossveins. Mediocubital space with two crossveins; CuA vein forked slightly beyond level of M fork, CuP unforked; intracubital space with single crossvein. Cubitoanal space with two crossveins; area between A1 and A2 with a single crossvein, A2 forked before R fork level; area between A2 and A3 with single crossvein. Hindwing 11 mm long, costal field narrow, with four crossveins; subcostal field with single crossvein. Radial space with three crossveins, RP with two branches, basal one forked near posterior wing margin. Radiomedial space with three crossveins. M vein forked near mid-length of wing, intramedial space with two crossveins. Mediocubital space with two crossveins; Cu forked near wing base, CuA forked at apex; intracubital space with single crossvein. Cubitoanal space with single crossvein. Area between A1 and A2 with a single sinuous crossvein, A2 forked near wing base.

ABDOMEN. Dissected and cleared.

MALE GENITALIA. Unknown.

FEMALE GENITALIA ( Fig. 10 ). Sternite 8 unmodified, densely covered by long setae; gonocoxite 8 as small, paired, ovoid sclerites; gonapophyses 8 as lateral smooth, glabrous, ovoid plates. Tergite 9 ventrally extended in lateral view, expanded and articulated to gonocoxite 9, posteroventral margin straight; gonocoxite 9 ovoid, uniformly setose; gonostylus 9 small, semicircular, posterodorsally located on gonocoxite 9; ectoproct as a small ovoid sclerite, setose.

Distribution

Bolivia (probably Santa Cruz) ( Fig. 7C ).

Remarks

Ilyobius bimaculatus is only known from the holotype female, which is in poor condition. Consequently, understanding the phylogenetic affinities of this species is difficult at present because the primary diagnostic characters are currently limited to the male genitalia. However, the color pattern of this species is similar to that of I. flammatus (Penny, 1982) , I. mexicanus (Banks, 1901) and I. curvatus Liu et al., 2015b . In those species, the pronotum is uniformly orange and the head has posteriorly trifurcate dark markings around the compound eyes. Ilyobius bimaculatus can easily be distinguished by having the frons possessing a pair of ovoid black spots between the antennal fossae, which are absent in the other species.

Figures

Fig. 8. Holotype female of Ilyobius bimaculatus (Banks, 1920), dorsal habitus.

Fig. 9. Holotype female of Ilyobius bimaculatus (Banks, 1920). A. Head, dorsal view. B. Head, dorsofrontal view. C. Fore- (above) and hindwing (below).

Fig. 10. Holotype of Ilyobius bimaculatus (Banks, 1920), female genitalia. A. Lateroventral view. B. Lateral view. C. Morphological interpretation of genital sclerites in B. D. Ventral view.

Fig. 7. Distribution of species of Sialidae (Megaloptera) studied herein. A. Distribution of Caribesialis bifasciata (Hagen, 1861) comb. nov., Ilyobius bimaculatus (Banks, 1920), and I. nigrocephalus sp. nov. B. Distribution of C. bifasciata comb. nov. in Cuba. C. Distribution of I. bimaculatus in Bolivia. D. Distribution of I. nigrocephalus sp. nov. in Ecuador.