Mastigusa arietina (Thorell, 1871)

Mastigusa arietina (Thorell, 1871) View in CoL

Figs 1, 2 View FIGURES 1–3 , 4–7 View FIGURES 4–9 , 10, 11 View FIGURES 10–12 , 13–18, 22

Mastigusa macrophthalma View in CoL : Deltshev, 1990 [misidentification]; Deltshev et al., 2011 [misidentification]

Material examined. Bulgaria: 1♂, Pirin Mts. , 41.7877, 23.3248, Pinus forest, under stone, 23 August 2023, leg. Viktor StřeštÍk (CVS) GoogleMaps ; 1♀ (DD196), Sofia Basin, Balsha Village 42.85854, 23.25959, xerothermic grassland, inside a Messor sp. ant nest under a stone, 15 March 2024, leg. Simeon Indzhov (NMNHS) GoogleMaps ; 1♂, Vitosha Mts., Knyazhevo 42.65573, 23.240804, old growth Pinus forest plantation, under stone, 12 November 2024, leg. Simeon Indzhov (NMNHS) GoogleMaps ; 1♀ (DD200), Belasitsa Mts., above Kongura Hut , 41.3414, 23.1853, Fagus forest, pitfall trap, 15 November 2024, leg. Vihra Haynadzhieva (NMNHS) GoogleMaps ; 1 ♀ (DD194), Sofia Basin, Sofia, Seminary Wall 42.67644, 23.33653, 30 January 2025, leg. Simeon Indzhov (NMNHS) GoogleMaps ; 3♂♂ (DD193), 1 ♀ (DD195), Black Sea Coast, Nessebar 42.66570, 27.71162, beach, in a rotting log, 17 November 2024, leg. Galin Ivanov (NMNHS). (https:// www.inaturalist.org/observations/251684457) GoogleMaps .

Diagnosis. Diameter of conductor of male palp above 1.5 mm; conductor diameter / cephalothorax length ratio>1 (see Castellucci et al. 2024), RTA with a hook-shaped tip and VTA long and thin ( Figs 5, 7 View FIGURES 4–9 ). Female vulva approximately 0.33 mm long, copulatory ducts with multiple dense coils and wide lumen (Figs 13, 16). Posterior eyes variable but small, usually separated by at least one eye diameter ( Figs 1, 2 View FIGURES 1–3 , 10, 11 View FIGURES 10–12 ).

Remarks. This species is currently known from several localities in Bulgaria, primarily located in the Western part of the country, with the exception of the somewhat different population from the Black Sea coast ( Fig. 22 View FIGURE 22 ). However, the territory of Bulgaria has not been completely sampled and further faunistic research is needed. The species is generally considered myrmecophilous but most individuals we collected were not found near ant nests, except specimen DD196 from the vicinity of Balsha, which was found in the nest of Messor cf. structor . The male from Knyazhevo was found under a stone, not near an ant nest. As the area has been searched by the first author multiple times over the years, this species may be generally subterranean and difficult to find, with only wandering males occasionally being found under stones. Nests of black-coloured Lasius sp ( Formicidae : Formicinae ) were found in the general area. It is also unclear whether the specimen from the Pirin Mts. was found in an ant nest, as the collector does not recall observing ants at the collection spot. Both male specimens were found in pine forests/ plantations. The specimen from the city of Sofia was walking on the outer wall of a building in broad daylight, so it was presumably disturbed and was not in its typical microhabitat. As the old and forest-covered park Borisova Gradina is in the immediate vicinity, it is likely a population exists there.

Although the individuals from Western Bulgaria fit into the clade containing the other European specimens in the tree, the ones from the Black Sea coast form a distinct subclade but are still within the M. arietina clade (DD193 + DD195; Fig. 23 View FIGURE 23 ). The support for this subclade is very low. There are subtle differences in the male palp morphology, with a more curved VTA and a longer and slimmer CdP ( Figs 6, 7 View FIGURES 4–9 ), more similar to M. diversa ( Figs 8, 9 View FIGURES 4–9 ) than to the typical M. arietina ( Figs 4, 5 View FIGURES 4–9 ). No other differences were observed, neither in the shape of the RTA, nor in the female morphology or eye size ( Figs. 10, 11 View FIGURES 10–12 , 13–18), between this population and the typical M. arietina . Given that Castellucci et al. (2024) did not split the genetically much more distinct populations from Georgia and Finland into separate species, we consider these differences a polymorphism until further material, ideally from a broader area is available.

FIGURES 13–21. Female genitalia. 13–18. M. arietina . 19–21. M. macrophthalma . 13, 16, 19 epigyna; 14, 17, 20 vulva ventral, 15, 18, 21 vulva dorsal. Scale line: 0.2 mm.