Nesting biology and mating behavior of the solitary bee <i>Epicharis nigrita</i> (Apoidea: Centridini)

Centridini bees are key pollinators of many wild and cultivated plant species, but data on their biology remain limited. An aggregation of nests of <i>Epicharis nigrita</i> was studied in an urban area during four nesting seasons (generations). <i>Epicharis nigrita</i> is a univoltine species and nests are built during 3.5 months per year (middle November to February). Females dig their nests in flat, bare or sparsely vegetated sandy soil. The peak in nest density occurred at the end of December or in the first week of January (3.0–32.3 nests/m²), corresponding to 900–9690 estimated nests in the area. Females performed about 10 flights/day and, unexpectedly, spent the night outside the nest. The average period of female activity in each nest was 6.9 d. Nests contained 4–5 brood cells, different from other observations of this species. Female plasticity in the duration of activities at nests, and consequently the number of brood cells produced per nest, is discussed. The first direct record of <i>Rhathymus bicolor</i> emerging from <i>E. nigrita</i> brood cells is provided. Males patrolled nest sites, where females mated with only one male despite attempts by 1–5 males to mate simultaneously with a female.