BROOD RAIDING IN THE FIRE ANT, SOLENOPSIS-INVICTA (HYMENOPTERA, FORMICIDAE) - LABORATORY AND FIELD OBSERVATIONS

One of the first activities of minim workers in incipient fire ant nests is mutual brood raiding, the reciprocal stealing of brood from nearby incipient nests. Brood raiding was observed in the fire ant, Solenopsis invicta Buren, in the laboratory and in the field. Raids were initiated by individual workers, usually from the larger nest, involved trail laying and following, and lasted from minutes to days. Aggression toward intruding workers was generally low and often absent. Workers in the losing nest occasionally raided for the intruding colony (traitor raiders). The colony with more workers was likely to win the raid. No other factors-number of queens, number or stage of brood, or minim relatedness-affected winning. Workers from the losing nest, and often queens too, defected to the winning one. In the field, reciprocal blood raiding was a major cause of incipient colony mortality. It took place along odor trails connecting various numbers of nests from a few centimeters to 20 m apart, and its effect was to aggregate the brood and workers from local populations of incipient colonies into a few locations. One brood raid lasted 38 d, with over 100 m of trail, and involved at least 80 incipient nests.