Cherries, Ants and Tent Caterpillars: Timing of Nectar Production in Relation in Relation to Susceptibility of Catepillars to Ant Predation

Abstract

The North American black cherry, Prunus serotina Ehrh., has extrafloral nectaries which are most active during the first 3 wk after budbreak. These nectaries attract large numbers of the ant Formica obscuripes Forel, especially to trees within °20 m of an ant colony. The average number of ant visits per bud is highest just after budbreak, decreasing as the number of active extrafloral nectaries decreases. These ants are predacious on many species of insects found on P. serotina, including the eastern tent caterpillar, Malacosoma americanum Fabricus, the major defoliator of black cherry. Formica obscuripes is only able to prey upon M. americanuum within °3 wk of budbreak, after which time, tent caterpillar larvae are large enough that most escape ant predation. Tent caterpillar survivorship was found to be positively related to distance from colonies of F. obscuripes. It is suggested that the ant—cherry relationship is a faculative mutualism and that nectar production is timed so as to maximize the chance of successful ant predation on tent—caterpillar colonies.