A method for year-round rearing of cuckoo bumblebees (Hymenoptera: Apoidea: Bombus subgenus Psithyrus)

The study of the social interactions between host bumblebees and their inquiline species requires rearing them. Here we provide a simple method for rearing of cuckoo bumblebees (Bombus subgenus Psithyrus) in the laboratory. Two bumblebee cuckoo-host systems are used: Bombus (Psithyrus) vestalis hosted by B. (Bombus) terrestris and B. (Psithyrus) sylvestris hosted by B. (Pyrobombus) pratorum. First, the invasion of the Psithyrus female is performed in species-specific host colonies containing approximately 10 young workers. On average, a parasitized colony of B. terrestris produced 90 +/- 9 young males and 21 +/- 3 young females of B. vestalis, whereas a parasitized colony of B. pratorum produced 16 +/- 2 young males and 5 +/- 1 young females of B. sylvestris. One week after emergence, Psithyrus virgin females are placed in a flight cage exposed to natural light, with Psithyrus males of other colonies. After successful mating, the females are isolated and overwintered in a cold room at 4 degrees C for 2-4 months. This method enables a year-round and mass breeding of Psithyrus species to facilitate studies of these rare species.