Oecanthus dulcisonans Gorochov, 1993

Silva, Hugo Miguel, Avivar-Lozano, Laura, Gomes, Goncalo, Rhee, Howon, Dellinger, Thomas & Aguin-Pombo, Dora, 2024, New records of Oecanthus species (Orthoptera, Oecanthidae) in the Madeira archipelago, Journal of Orthoptera Research 33 (1), pp. 95-102 : 95

Oecanthus dulcisonans Gorochov, 1993

Fig. 2A, B, D, G

Material examined. -

PORTUGAL • 16♂, 1♀; Madeira Island, Machico, Caniçal, Ponta de Sao Lourenco ; 32°44'37"N, 16°42'05"W; 76 m a.s.l.; 16.VI.2023; H. Silva, G. Gomes, T. Dellinger, H. Rhee leg.; on: Hyparrhenia hirta ; UMACI • 3♂, 1♀; Madeira Island, Santa Cruz, Caniço, Reis Magos ; 32°38'56"N, 16°49'23"W; 38 m a.s.l.; 19.VI.2023; H. Silva, G. Gomes, H. Rhee leg.; on: Hyparrhenia hirta ; UMACI • 1♂; Porto Santo Island, Campo de Baixo ; 33°2'53.39"N, 16°21'5.86"W; 16 m a.s.l.; 23.X.2022; H. Silva, D. Aguín-Pombo, L. Avivar-Lozano, M. Dias leg.; on: Hyparrhenia hirta ; UMACI .

Measurements. -

MADEIRA ISLAND - ♂: BL=14.44 ± 0.55 mm (n=19); EL=14.18 ± 0.68 mm (n=19); HW=2.59 ± 0.32 mm (n=19); FL=7.98 ± 0.50 mm (n=19); ♀: BL=14.08 ± 0.39 mm (n=2); EL=14.10 ± 0.55 mm (n=2); FL=7.85 ± 0.63 mm (n=2); OV=5.48 ± 0.32 mm (n=2). PORTO SANTO ISLAND - ♂: BL=17.34 mm (n=1); EL=13.28 mm (n=1); HW=2.00 mm (n=1); FL=7.03 mm (n=1).

Sounds. -

The song of the species consists of continuous long echemes without gap, as has been already mentioned ( Gorochov 1993, Cordeo et al. 2009) as a conspecific song trait (Fig. 3C ).

Notes. -

Oecanthus dulcisonans is primarily distinguished from O. pellucens by the shape of the metasternal plate. In the specimens of O. dulcisonans , this plate is longer and thinner than the metasternal plate of O. pellucens (Fig. 2A, D-F ). In terms of size, the specimen from Porto Santo measured 17.34 mm in body length, slightly exceeding the 14.00-17.00 mm reported for this species in other works ( Gorochov 1993, Cordero et al. 2009, Braud et al. 2015, Reitmeier 2018). However, specimens from Madeira, both male and female, fall within the size range. In contrast, some measurements differ from previous publications. For example, the mean length of the hind femur was 7.98 ± 0.50 mm for males from Madeira and 7.03 mm for the male from Porto Santo, deviating from the 8.70-10.00 mm range reported in other studies ( Gorochov 1993, Cordero et al. 2009). Additionally, the mean length of the protruding wing was 2.59 ± 0.32 mm for specimens from Madeira and 2.00 mm for those from Porto Santo, which is less than the 3.00-4.00 mm reported in other studies ( Braud et al. 2015, Reitmeier 2018) (Table 1 ). Notably, the mean length of the oviscape in females exceeded the value reported by Braud et al. (2015). The specimen from Porto Santo was discovered stridulating on a stem within a one-meter-high patch of spontaneous herbaceous vegetation, predominantly characterized by Hyparrhenia hirta E. Fourn. This habitat was located between buildings (Fig. 4A ). Several individuals were also heard during the night along the southwest coast of Porto Santo in the vicinity of Praia do Zimbralinho, Cabeço da Ponta, and Campo de Baixo (Fig. 1 ). Similarly, specimens from Madeira were observed stridulating on stems in patches dominated by H. hirta , on Ponta de São Lourenço and Reis Magos, with the presence of plant species such as Euphorbia piscatoria Aiton, Echium nervosum Dryand., and the invasive Opuntia tuna (L.) Mill. on Reis Magos (Fig. 4B ). Several individuals were also heard at night in Garajau and Porto Novo.

Figures

Fig. 1. Records of Oecanthus spp from Madeira and Porto Santo Islands. Data sources: authors' field sampling (collected specimens and acoustic records), literature (Chopard 1938, Lange 1990) and online databases (GBIF 2022).

Fig. 2. Oecanthus dulcisonans (A, B, D, G) and Oecanthus pellucens (C, E, F, H) from Madeira archipelago. Metasternal plate (the dots represent parts of the structure that were not visible to draw) (A, D, E, F), body in dorsal view (B, C), and epiphallus in dorsal view (G, H). Photos: Thomas Dellinger. Scale bars: 1 mm (A, D, E, F); 10 mm (B, C); 0.5 mm (G, H).

Fig. 3. Photos of Oecanthus dulcisonans stridulating (A) and standing (B) on Hyparrhenia hirta E. Fourn at Ponta de Sao Lourenco, Machico, Madeira Island on June 17, 2023. Photos: Howon Rhee. Oscillograms of songs of O. dulcisonans recorded at 23 ° C in Porto Santo Island (C) and Oecanthus pellucens recorded at 22.5 ° C in a laboratory with an individual from Spain by Klaus-Gerhard Heller (D), from the Orthoptera Species Files Online (Cigliano et al. 2023).

Fig. 4. Habitats of Oecanthus dulcisonans in Madeira and Porto Santo: A. Campo de Baixo, Porto Santo Island. Photo: Tome Freitas; B. Reis Magos, Canico, Madeira Island. Photo: Hugo Silva.