Lasioglossum costulatum

Lasioglossum costulatum (Kriechbaumer, 1873) Conservation status CR Distribution Lasioglossum costulatum reaches the septentrional edge of its distribution in Poland and Belgium, extending southwards to Morocco and as far east as Irkutsk (Russia). In Belgium, this species has always been very rare and is now restricted to the Gaume Region (Pauly and Vereecken 2018). Restoring this species’ habitat involves maintaining and expanding forest gaps in order to enhance the abundance and diversity of Campanulaceae (Braun-Reichert et al. 2021). Notes This species is mainly observed along forest edges, in thermophilic habitats such as nutrient-poor meadows, quarries and railway embankments - though one of the specimens was also collected on a wet grassland. Nests are constructed in soils rich in sand or loess (Westrich 2018). The Campanulaceae are its preferred source of pollen (Pesenko et al. 2000). However, we observed it on three other plant families, where it may have been foraging for nectar. Although L. costulatum is generally considered solitary, some evidence suggests it may form communal aggregations (Pesenko et al. 2000). Females emerge from diapause in late April, while males begin flying from July onwards (Westrich 2018). Diagnosis This species is one of the many Lasioglossum featuring tergites with dark hind margins and a carinate propodeum (Fig. 13). Both males and females can be identified by the hexagonal shape of the posterior face of their propodeum, which features strong parallel wrinkles (Pauly 2015 a).