Plecia sp.

Schelesky-Prado, Daniel de Castro & Falaschi, Rafaela Lopes, 2023, Notes on presumed Neotropical records and species of Hesperinus Walker, 1848 (Diptera: Bibionidae), EntomoBrasilis (e 1059) 16, pp. 1-6 : 2

Plecia sp. ( Figures 1 A-C, 2)

Material examined. 1 male [ BRASIL, São Paulo] Monte Alegre [do Sul], Fazenda Sta. [Santa] Maria , Alt. [Altitude] 1.100 mts. [1,100 m], 24-30.XI.1942, F. Lane col. ( MZUSP) ; 1 male, label 1: BRASIL - SÃO PAULO, Monte Alegre [do Sul], Faz. [Fazenda] N.S. [Nossa Senhora] [Da] Incarnação [Encarnação], 750 ms. [m] 14.27- X-1942, L. Trav. F. & Almeida; label 2: Hesperinus sp ., ♂, M. CARRERA DET. 1943 ( MZUSP) .

Comments. CARRERA (1944) reported three specimens of Hesperinus sp. from the municipality of Monte Alegre do Sul , state of São Paulo, Brazil. He mentioned one male and one female from Faz. [Fazenda] N. S. [Nossa Senhora] [Da] Encarnação (750 mts. [m]), 14/27-X-42, L. Trav. F. & Almeida col., and one male from Faz. [Fazenda] Sta. [Santa] Maria (1.100 mts. [1,100 m]), 24/ 30-XI-1942, F. Lane col. Only the two male specimens were located in the MZUSP collection.

The specimens are not Hesperinus . Firstly, the male eyes are holoptic ( Figure 1C ), while they are dichoptic in Hesperinus (see HARDY 1981, p. 219, Figure 13.2). Secondly, the antennal flagellomeres are compact and compressed, except for the first flagellomere ( Figure 1A ). This contrasts with the filiform flagellomeres of Hesperinus , in which each article is longer than wide, excluding the apical segment (see HARDY 1981, p. 219, Figure 13.2). Thirdly, the vein R 2+3 is relatively short (less than a third of the length of R 4+5) and slightly oblique with respect to R 4+5, and has a distinct basal bend ( Figure 1B ), unlike the relatively medium length (almost half the length of R 4+5), more distinctly oblique with respect to R 4+5, and without a distinct basal bend as in Hesperinus (see HARDY 1981, p. 220, Figure 13.8). Additionally, the R 2+3 is not sinuous ( Figure 1B ), unlike Hesperinus , which may present a slight (see HARDY 1981, p. 220, Figure 13.8) or prominent (see KURINA 2013, p. 3, Figure 2b ) sinuosity. Lastly, the apex of R 4+5 is only slightly arched posteriorly ( Figure 1B ), rather than being distinctly arched posteriorly as in Hesperinus (see HARDY 1981, p. 220, Figure 13.8) ( FITZGERALD 2004).

A synapomorphic character of Bibionidae , excluding Hesperinus , is the presence of holoptic eyes in males ( PINTO & AMORIM 2000; FITZGERALD 2004). However, in a few species such as Penthetria funebris Meigen, 1804 and P. conjungens , males are dichoptic ( HARDY 1967; FITZGERALD 2004). Hesperinus consistently exhibits dichoptic eyes, usually widely separated, as seen in H. brevifrons and H. nigratus , although it can be weakly dichoptic, as seen in H. macroculatus ( FITZGERALD 2004; SKARTVEIT 2009; PAPP 2010). Another synapomorphy of Bibionidae , excluding Hesperinus , is the presence of compressed antennal flagellomeres in males ( FITZGERALD 2004). The R 2+3 of Plecia is relatively short and can be oblique, curved, straight, or even with a distinct basal bend ( FITZGERALD 2004). In Hesperinus , R 2+3 is relatively medium in length (usually longer than Plecia and shorter than Penthetria ) and oblique ( FITZGERALD 2004). However, in fossils of Hesperinus the length of R 2+3 can be more variable than in extant species, i.e., shorter or longer with respect to R 4+5 ( SKARTVEIT 2009). The distinctly arched posterior apex of R 4+5 is a synapomorphy of Hesperinus ( FITZGERALD 2004) . Based on our observations, it is evident that the specimens do not belong to Hesperinus . They can also not be Bibioninae, as the vein R 2+3 is present and the fore tibia lacks a strong apical spine seen in Bibionini or the sets of spines seen in Dilophus Meigen, 1803 ( FITZGERALD 2004). The remaining options are Penthetria and Plecia . The specimens have a diagnostic feature of Plecia , which is a short R 2+3 and subparallel to R 4+5 (diagnosis for Penthetria ) ( FITZGERALD 2004). Hence, they do not belong to Penthetria , but to Plecia .

Since Carrera identified these specimens only to genus, we decided here to correct his genus misidentification and assign it to Plecia rather than Hesperinus . This material can be identified at the species level or even described as a new species in a further study, which is not the scope of the present study.

Figures

Figure 1. Plecia sp., male. A. Habitus, lateral view. Scale bar: 5 mm. B. Wing. Scale bar: 2 mm. C. Head, dorsal view. Scale bar: 1 mm.

Figure 2. Plecia sp., male. Habitus, lateral view. Scale bar: 5 mm.