ARTHROPODS ASSOCIATED WITH A MANZANITA GALL INDUCED BY THE APHID TAMALIA COWENI (COCKERELL) (HOMOPTERA: APHIDIDAE)

Abstract

AbstractGalls induced by the aphid Tamalia coweni (Cockerell) were sampled from greenleaf manzanita (Arctostaphylos patula E. Greene) in Shasta County, California. Thirty galls from each of four sites were collected over a 5-year period (1990–1994) at roughly weekly intervals (N = 5010). The contents of each gall were examined and recorded. Excluding T. coweni, 25 taxa were encountered representing eight arthropod orders: Acari, Thysanoptera, Hemiptera, Neuroptera, Coleoptera, Diptera, Lepidoptera, and Hymenoptera. All play a minor role in the gall community with the exception of two species of Diptera. The data suggest that Leucopis sp. and Heringia sp. are obligatory predators of T. coweni and coexist by partitioning the aphid resource with different exploitation strategies. Heringia sp. has a relatively low infestation rate (10.8%) but is a superior competitor. Leucopis sp. compensates for its inability to compete effectively with Heringia sp. by maintaining a higher infestation rate (41.4%).