Individuals used for the tests were placed singly in small glass vials (3.5 cm height 2.0 cm diameter). To decrease the agitation of the collected bee, the glass vials were kept in ice for about 2 min. The bee was then removed from the vial and introduced into the experimental box through the introduction tube. Interactions between the introduced individual and the residents were recorded for 5 min after the introduction. Aggressive displays, such as biting of wings or legs, immobilization, and resin deposition were considered as rejection, while absence of aggressive behaviour and entrance of the individual into the main colony box was considered acceptance. Only one individual was introduced per test, a 15 min interval was allowed between introductions, and each collected individual was tested only once.