Small males emerge earlier than large males in Dawson's burrowing bee (Amegilla dawsoni) (Hymenoptera: Anthophorini)

Females of Dawson's burrowing bee ( Amegilla dawsoni ) are receptive to the males as they emerge but have become unreceptive by the time they begin to nest. In addition, there is a single emergence period per year lasting about a month. These factors are predicted to lead to protandry and males of Dawson's burrowing bee do tend to emerge earlier in the annual flight season than females. Moreover, even during a single day, emerging males tend to precede females. The degree of protandry, however, is size-dependent, with smaller males tending to precede larger ones, both over the course of the flight season and on any given day. Because small males are at a disadvantage in the fights that occur for females, the earlier emergence of minor males may be a sexually selected response that reduces the likelihood that they will be displaced from potential mates by larger rivals.