Thyridosmylus Krueger

Xu, Han, Winterton, Shaun L., Wang, Yongjie & Liu, Zhiqi, 2017, Two new species of Thyridosmylus Krueger, 1913 from Madagascar (Neuroptera, Osmylidae), ZooKeys 724, pp. 43-52 : 44-45

Genus Thyridosmylus Krueger

Thyridosmylus Krüger, 1913: 87. Type species: Osmylus langii McLachlan, 1870: 197. Original designation. Type locality: Masuri (India).

Centrolysmus Navás, 1917: 15. Type species: Osmylus perspicillaris Gerstaecker, 1884: 46. Original designation. Type locality: Darjeeling (India).

Diagnosis.

Medium sized species (forewing length 13-24 mm), wings narrow (maximum width of forewing 4-7 mm). Ocelli present. Forewing strongly patterned with distinctive fenestrate spots close to the outer gradate series, with numerous suffusions, some of these forming a large macula, numerous crossveins. Costal crossveins simple, subcostal space with single crossvein. At least two distinct gradate series. Area between M and Cu lacking crossveins between them basally, thus a large cell is present. Hindwing with Cu forked at base, CuP short and not pectinate. Male ectoproct bearing a dorsal digitiform projection, gonarcus symmetrical, amalgamated distally, sclerotized marginally; baculum present; mediuncus C-shaped, linked by membranes; parameres present. Female genitalia with sternite 8 small, gonapophyses 9 as paired sclerites closely associated with gonocoxites 9, spermatheca simple or with a complicated lobed morphology.

Redescription.

Body length 10-15 mm. Head brown or dark brown; antennae yellow and shorter than or equal to half of length of forewing, scape and pedicel dark brown, flagellum yellow; compound eyes black; ocellar tubercles yellowish to brown; labrum brown or dark brown. Thorax dark brown with long setae; meso- and metathorax dark brown. Legs yellow with brown setae. Forewing length 13-24 mm, width 4-7 mm. Forewing generally with characteristic fenestrate spots near the outer gradate series and with numerous fuscous markings, membrane hyaline or with light infuscate suffusion; pterostigma brown with a light brown centre; two nygmata as brown spots; venation brown, some cross-veins edged with brown markings; costal cross-veins simple and occasionally bifurcate; cross-vein sc-r1 close to the base of forewing; forewing Rs with 10-15 branches, cross-veins among Rs branches forming more than two series of gradates; basal mp-cu cross-vein only one, forming a large cell. Hindwing length 12-22 mm, width 4-7 mm. Hindwing generally hyaline with few spots; pterostigma light yellow; nygmata inconspicuous and light brown; base of MP with a spur. Male genitalia. Tergite 8 and sternite 8 approximately quadrate. Tergite 9 commonly narrow, sternite 9 approximately trapezoidal or triangular; ectoproct with a dorsal process, callus cercus round; gonarcus sclerotized marginally, symmetrical and fused distally and base connected with a goblet-shaped anterior apodeme; entoprocesses bent in middle; mediuncus lobes bent into C-shape laterally and fused at base; parameres arch-like with medial thickening and invariant within genus. Female genitalia. tergite 8 broad and approximately quadrate; sternite 8 reduced and small; tergite 9 narrow and commonly constricted in middle articulated with gonopophysis 9 + gonocoxite 9; gonocoxite 9 finger-like in lateral view; each spermatheca connected with a spermathecal duct.

Comments.

The distinction between the closely related Thyridosmylus and Spilosmylus has been historically ambiguous, although their reciprocally monophyletic sister-group relationship was confirmed in the phylogeny of the family by Winterton et al. (2017). Traditionally, Thyridosmylus was characterized by numerous markings of forewings with the often presence of distinct fenestrations around the outer gradate cross veins, while the forewings of Spilosmylus are characterised by having fewer maculations and an embossed spot along the posterior wing margin, or intermittent dark streaks between Sc and R1. As more species have been described it seems that these characters could not completely separate these genera, with numerous instances where the diagnos tic feature of either genus is lacking. With regard to Thyridosmylus , fenestrate markings are not found in several species such as T. fuscus Yang, 1999, T. longiprocessus Xu, Wang & Winterton, sp. n., T. maolanus Yang, 1993, T. marmoratus Fraser, 1955, T. pallidius Yang, 2002 and T. trifasciatus Yang, 1993. Still, the forewings of these species exhibit extensive fragmental markings and do not possess embossed spots and intermittent streaks typical among Spilosmylus species. Additionally, the spermathecae in some Thyridosmylus species (e.g., T. langii , T. paralangii and T. fuscomarginatus Xu, Wang & Winterton, sp. n.) are complex and multilobed, resembling those of some Spilosmylus species. The shape of the external genitalia in the males of Thyridosmylus varies less compared with Spilosmylus .

The forewing of Thyridosmylus has two m-cu cross veins between the stem of the medial vein (before the split into MA and MP) and cubital vein to form single large cell, while the forewing of Thaumatosmylus has few fuscous spots, and three m-cu cross veins to form two basal cells. Also, the spermathecae in females of Thyridosmylus are elliptical or multilobed while the spermathecae in Thaumatosmylus tend to be large with a basal club-like sac, or with a small and apical finger-like to ovoid sac. Although the definition of genus Glenosmylus has been obscure since it was erected by Krüger (1913), it can be distinguished from Thyridosmylus based on three m-cu cross veins in the forewing character, similar to that found in Thaumatosmylus .

Key to Thyridosmylus species in Madagascar