Differential Use of Pin and Black Cherry by the Eastern Tent Caterpillar Malacosoma americanum Fab. (Lepidoptera: Lasiocampidae)

Abstract

Pin and black cherry (Prunus pennsylvanica and P. serotina) occur frequent- ly in the northeastern U.S. in single and mixed species stands. However, the eastern tent caterpillar (Malacosoma americanum) is only rarely found on pin cherry. For exam- ple, in several infested, mixed-species stands in New England, 3 - 967% (mean = 58.4 %o) of black cherry trees examined had one or more egg masses of the eastern tent caterpillar on them. Only 0-7 %o (mean = 2.3 %) of pin cherry trees in the same stands had egg masses on them. Field transplant studies of larvae revealed that although they were able to survive and grow on pin cherry, larvae grew more slowly and reached a smaller late instar size than those growing on black cherry in the same stands. Greenhouse growth ex- periments showed that Malacosoma americanum could reach the adult stage on pin cherry, but they were smaller than siblings grown on black cherry. Siblings raised on pin cherry also grew slower. This growth rate difference was greatest early in the larval stage, sug- gesting the influence of chemical or physical differences in young pin and black cherry leaves. Larval choice experiments in the greenhouse revealed that larvae (3rd instar) ac- tively chose black cherry over pin cherry even when raised on pin cherry. We hypothesize that lack of use of pin cherry by eastern tent caterpillars reflects its poor quality as a host plant relative to black cherry. However, the contact between this species and pin cherry may be historically recent and Malacosoma americanum may still be