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 vialswere 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 residentswere 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 individualwas tested only
once.