AGE POLYETHISM AND DEFENSE IN A TROPICAL SOCIAL WASP (HYMENOPTERA, VESPIDAE)

Although tapping the nest in simulated vertebrate attack caused all but 1-day-old workers of Polybia occidentalis to rush from inside and cover the envelope, defense itself-attack of a target-was shown to be carried out only by workers older than about 10 days. While foraging was also performed by older workers, the frequency-age distribution of defensive behavior was skewed to a significantly younger age than was that of foraging. The plot of mean individual probability of defending as a function of age was logistic, leveling off at 0.11 by the age of about 13 days. The distribution of the probability of defending among workers greater-than-or-equal-to 13 days of age was random, indicating that there is no specialized defender class among older workers. Workers that defended were recruited from among both nest workers and foragers. Although foragers were more likely to defend than were nonforagers, nonforagers contributed more individuals to the pool of defenders because they were more numerous.