Ilyobius brasiliensis (Navás, 1936)

Mendes, Gabriela Caroline, Nascimento, Jeane Marcelle Cavalcante Do, Fusari, Lívia Maria & Hamada, Neusa, 2024, Updates on the taxonomy of Ilyobius nubilus (Navás, 1933) (Megaloptera: Sialidae: Sialinae) and Ilyobius brasiliensis (Navás, 1936) from southeastern Brazil, Zootaxa 5406 (1), pp. 123-140 : 138-139

Ilyobius brasiliensis (Navás, 1936) , sp. rev.

( Fig. 12A–C )

Protosialis brasiliensis Navás, 1936: 36 (original description); Contreras-Ramos 2006: 980 (redescription). Heckman 2017: 78 (key of species)

Ilyobius brasiliensis ; Liu et al. 2015a: 31 (phylogeny of Sialidae ; comb. nov.)

Material examined. Holotype: gender unknown (abdomen missing), Brazil; São Paulo, Ypiranga 09.xi.1896, Luederwaldt ( MZUSP).

Taxonomic notes. Head ( Fig. 12A, B ): length = 1.5 mm; width (at the widest point) = 1.9 mm; region between the posterior margin of the eyes = 1.6 mm. Forewing: length = 9 mm; width = 2.7 mm; 4X longer than wide proximally, 3X longer than wide distally; posterior margin almost straight ( Fig. 12C ). Specimen deteriorated, lacking abdomen, genitalia, antenna flagellum and hindwings, only remaining left forewing.

Distribution. BRAZIL, São Paulo State.

Remarks. In addition to same distribution area, similarities on forewing shape and general coloration were characters used by Liu et al. (2015a) to support I. brasiliensis as junior synonym of I. nubilus . However, the color pattern seems to be well conserved within the Ilyobius species groups (e.g., members of I. mexicanus group share an orange head with postero-ocular black marks, in contrast to the I. chilensis group, I. nubilus and I. hauseri , which share a black head on vertex, orange laterally). Furthermore, the similarities on forewing shape of I. brasiliensis and I. nubilus was not corroborated in this study. Although these two species share the forewing costal area slightly expanded and with similar wing venation, the general shape of the forewing is different in each species. In I. nubilus the forewing is 3X longer than wide proximally, 3X longer than wide distally, and the posterior margin is slightly rounded ( Fig. 12D ). On the other hand, in I. brasiliensis the forewing is 4X longer than wide proximally, 3X longer than wide distally, and the posterior margin is almost straight ( Fig. 12C ). Liu et al. (2015b) highlighted an important diagnostic characteristic of I. nubilus : MA vein of hindwing proximally with a veinlet fused to MP ( Liu et al. 2015b) ( Fig. 6B ); however, it was not possible to verify this characteristic because the hindwings of I. brasiliensis holotype because they are missing and were not previously described. Therefore, based on available evidence, I. brasiliensis is here hypothesized as a valid species.

Ilyobius brasiliensis seems to be closely related to I. nubilus by sharing the general body color, both species have a brown to black head, with two lighter regions extending laterally from the gena region to the base of the head. Thus, I. brasiliensis appears to belong to I. chilensis group because it has a dark pronotum similar to that of other members of this group.

Ilyobius is difficult to sample in field studies, which is reflected in few studies on the genus and low representation of specimens in zoological collections ( Contreras-Ramos 2008). In addition, the lack of type material and poor conditions of type specimens are difficulties to be overcome in order to elucidate the taxonomic status of Ilyobius species. Collection of specimens at the type locality and laboratory rearing make it possible to fill gaps in knowledge about the taxonomy and biological traits of these rare insects.

Figures

FIGURE 6. Ilyobius nubilus, male. (A) forewing; (B) hindwing, the arrow indicates the veinlet between MA and MP. Scale bars = 2 mm.

FIGURE 12. (A–D) Ilyobius brasiliensis, holotype; (A) head, lateral; (B) head, dorsal; (C) hindwing; D) holotype information; (E) Ilyobius nubilus, hindwing, female. Scale bars, A, B = 0.5 mm; C, E = 2 mm.