A study of the life history of the solitary bee Monoeca xanthopyga, was conducted at the Araucária Plateau, at the state of Rio Grande do Sul. The study focused the seasonality, sexual behavior, females activity during nest building, the exploited plant resources and the associated parasitoids. Three nest aggregations of M. xanthopyga built in clay soil with few plant cover or none at all, were studied on the Parque Nacional dos Aparados da Serra, located in Cambará do Sul, Rio Grande do Sul State. The nests were randomly distributed in areas up to eight square meters in size and reach a maximum density of 57 nests per square meter. The only one generation occurred from January to April. The immature stayed in diapausa in the prepupa stage during eight to 11 months. Males emerged a few days before females, and disappeared from the aggregations four days before the end of females activities. The search for females to mate occurred at nests from the previous year, where many males struggled for a single emergent female. It is suggested that males perceive smells emitted by females. Copulation's lasted, on average, 26 seconds and, immediately after it, the couple separated. Nest building females were not attractive to males. Mating tests, at artificial environments showed the occurrence of copulation with both virgin and fertilized females. After mating, the females returned to the aggregations and established new nests by digging new tunnels, or by using abandoned nests. The bee's flying activities began around 6 A.M. and lasted up to 6 P.M. The females did, on average, eight trips per day, each one lasting 31,4 minutes. They returned from the trips carrying pollen and/or floral oils. These resources were obtained from flowers of Malpighiaceae and Fabaceae species. Pollinaria from orchids of the genus Oncidium Sw. were carried accidentally by males and females. Mutilid parasitoids were present at the aggregations of M. xanthopyga during all the period of the activities. One species of Traumatomutilla André, 1903 was related to the immature of these bees, composing the first registration of inhabitant of this Mutillidae.
Floral rewards; Monoeca xanthopyga; nest aggregations; parasitoids; reproductive behavior; seasonality; Tapinotaspidini
