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

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Abstract
Galls induced by the aphidTamalia coweni(Cockerell) were sampled from greenleaf manzanita (Arctostaphylos patulaE. 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. ExcludingT.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 thatLeucopissp. andHeringiasp. are obligatory predators ofT.coweniand coexist by partitioning the aphid resource with different exploitation strategies.Heringiasp. has a relatively low infestation rate (10.8%) but is a superior competitor.Leucopissp. compensates for its inability to compete effectively withHeringiasp. by maintaining a higher infestation rate (41.4%).