Aiolopus thalassinus (Fabricius, 1781)

Felix, Rob, Bouwman, Jaap, Odé, Baudewijn, Ketelaar, Robert, Pham, Duc Minh & Bailey, James, 2025, The grasshoppers and crickets (Orthoptera) of the Socotra Archipelago (Yemen): a comprehensive overview and a description of a new Oecanthus Tree Cricket (Oecanthidae), Contributions to Entomology 75 (1), pp. 21-166 : 21-166

Aiolopus thalassinus (Fabricius, 1781) s

Figs 67 , 68

References for Socotra.

Burr 1903: 412, 417 [as Epacromia thalassina ]; Krauss 1907: 19, 29 [as Epacromia thalassina ]; Popov (in Uvarov and Popov (1957)): 379; Hollis 1968: 343, fig. 84; Wranik 1998: 171; Wranik 2003: 324, plates 153, 158; Hemp and Rowell 2020: 119.

Diagnostic notes.

Aiolopus thalassinus is the only representative of the genus in the Archipelago. Its habitus is slender, with long wings and slender femora and its general colouration varies from green through brown, with markings of all shades of brown to whitish. The pronotum is weakly saddle-shaped and has a contrasting pattern of two white incurved lines bordered by dark markings, suggesting the presence of two lateral carinae (but they are absent) (Fig. 67 ). The hind wings are hyaline with a greenish hue, slightly infumated in the apex and posterior margin.

Taxonomic notes.

Hollis (1968) revised the genus Aiolopus Fieber, 1853 , distinguished seven species and provided a key. Since his revision, five extra species have been described ( Cigliano et al. 2024 a), amongst which Aiolopus puissanti Defaut, 2005 , a cryptic species resembling A. thalassinus . Aiolopus puissanti mainly occurs around the Mediterranean, but has recently been confirmed for Arabia, namely in Qatar ( Defaut 2021). Aiolopus puissanti can be separated from A. thalassinus by the shape of a dark marking on the tegmen: the dark transverse band in the tegmen situated at the level of the apex of the medial field is shallow. It does not extend caudally into the medial field when seen with open tegmen. It is much broader than high. In A. thalassinus , this transverse band is almost as broad as high. It penetrates from the frontal ridge caudally well into the medial field and, consequently, is almost square ( Defaut and Jaulin 2008; Defaut 2021). Furthermore, in A. puissanti , the tegmina extend much further beyond the hind knee (≥ 4.3 mm in males, ≥ 6.0 mm in females) than in A. thalassinus (≤ 4.2 mm in males, ≤ 5.5 mm in females) ( Defaut 2021). See Defaut and Jaulin (2008) and Defaut (2021) for illustrations of the wing patterns in both species and morphometric values for other parameters.

Hollis (1968) identified the taxon present on Socotra as the nominate ssp. of Aiolopus thalassinus . However, based on the shape of the dark marking on the tegmen, the material examined is quite variable. Some are typical for A. thalassinus or A. puissanti , while others show an in-between pattern. Based on the length of the tegmina extending beyond the hind knees in both males and females and the ratio of eye length to the length of the subocular furrow in females, Aiolopus specimens from Socotra identify as A. thalassinus (Table 4 ). However, the value of the latter parameter for males points towards A. puissanti , as does the value for the eye length ratio to the interocular space width (Table 4 ). Since the wing pattern is variable and not decisive in the Socotra specimens and wing length is considered one of the essential distinguishing parameters between the two species, we tentatively consider the taxon on Socotra to be A. thalassinus .

A thorough future molecular study of both Aiolopus species should give more insight into their status and the exact world distribution of both taxa.

Distribution and occurrence.

Aiolopus thalassinus is widely distributed in Europe, Africa and western Asia. On Socotra, it is widely distributed, but restricted to sites with suitable habitat, from Qalansiyah in the west to Arher in the east (Fig. 68 ). It is an abundant species on many sites, for example, in Wadi Zerig, Qeysoh and Adho Dimello.

Habitat and biology.

Aiolopus thalassinus is a phytophilous species that occurs in grassy vegetation along streams (Popov in Uvarov and Popov (1957)). In 2009 and 2010, the species was numerous in moist, grassy areas in wadis and wetlands, from 0–1450 m a. s. l. It may also be widely abundant in grazed fields and agricultural settings such as those that occur near villages. Records are from all seasons.

Bioacoustics.

Members of the genus Aiolopus emit quiet, buzzing sounds during rivalry, courtship and flight ( Roesti and Keist 2009). On Socotra, sounds have not been recorded.

Figures

Figure 67. Aiolopus thalassinus (Fabricius, 1781), male. Adho Dimello, Socotra, 31 Jan 2024 (photograph James Bailey).

Figure 68. Distribution of Aiolopus thalassinus (Fabricius, 1781) in the Socotra Archipelago.