DEFENSE AGAINST INTRASPECIFIC USURPATION BY PAPER WASP COFOUNDRESSES (POLISTES-FUSCATUS, HYMENOPTERA, VESPIDAE)

We conducted extensive field observations (369.6 h) and surveys of 36 preworker. multiple-foundress colonies of the social wasp Polistes fuscatus. We observed 48 intrusions by foreign conspecifics in 18 of 36 colonies. The rates of intrusion by foreign females, about 1 intrusion per colony each day, did not differ among observations conducted approximately 22, 39, and 48 days after nest initiation. Thus, it 'appears that usurpation pressure is both intense and constant throughout the preworker stage of the colony cycle. None of the observed intrusions resulted in the replacement of resident foundresses, although surveys revealed that 2 of 36 multiple-foundress colonies were usurped. All 48 intrusions were by females that were unlikely to be closely related to the colonies they attempted to usurp. Resident foundresses exhibited highly intolerant behaviour toward intruders, and evicted them within 40 s of their landing on the nest. There was a pronounced division of labour between queens and subordinates in colony defence. When present together on the nest, queens were significantly more involved than their subordinates in repelling intruders. The vast majority of intruder evictions did not involve cooperation or joint effort by cofoundresses. Therefore, the ability of multiple foundresses to successfully defend against usurpation is probably due to the decreased probability that their nest is left unattended.