Figs. 148–157.
For synonymy see van Achterberg & Talebi (2014).
Diagnosis: Body length of both sexes is 8–12 mm, ovipositor 1.1–2.8 mm. A smaller species with a short ovipositor, ovipositor sheath 0.6–1.8× as long as third tibia. This species has a typically elongated malar space, which is the longest among all Gasteruption species in central Europe (length similar to basal width of mandible).
Distribution: (Fig. 157): Palaearctic species occurring in most of Europe and Asia, but recorded only in small numbers in all the countries of occurrence. Recorded from the following countries in Europe: Austria, Belgium, Croatia, Czech Republic, France, Germany, Greece, Italy + Sicily, Montenegro, Poland, Portugal, Russia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom (Ferrière 1946; Šedivý 1958; Hedqvist 1973; Oehlke 1984; Madl 1989; Pagliano & Scaramozzino 2000; Wiśniowski 2004, 2020; Broad & Livermore 2014; Strumia & Pagliano 2014; van Achterberg & Talebi 2014; Ceccolini 2016; van Achterberg 2019; Madl & Mitroiu 2019, and personal records). Recorded also in Asia from Iran, Kazakhstan, Kyrgyzstan, Mongolia and Turkey (van Achterberg & Talebi 2014, Özbek 2020, and personal records).
Šedivý (1958; 1989) recorded this species only from the Czech Republic (Bohemia and Moravia), not in Slovakia. In both countries, the species is rare and distributed only in warmer parts. It was recorded from 32 localities from the Czech Republic, while 17 records are after 1990. In Slovakia, it was unknown from published records, but the first localised findings date back to 1961 (a male from Štúrovo). In total, eight localities are known from Slovakia, of which five were recorded after 1990 (Tab. 2). The species is very local but numerous in some sites. A new species for Slovakia.
Biology: Recorded from May to August. Parasite of species of Colletidae, namely Hylaeus communis and Hylaeus punctatus (Wall 1994; Jakubzik & Cölln 1997; Orlovskyté et al. 2018), and probably also Hylaeus hyalinatus Smith (Esser & Cölln 2002). Adults visit flowers of plants of families Apiaceae, Asteraceae and Saxifragaceae (Saxifraga aizoides) (Wall 1994).
Conservation: Rare species, sometimes numerous at localities. Occurs in both countries, while it is restricted with the distribution to the warmest parts of both countries. NT—near threatened (Tab. 2).