Biogeographical information concerning the common subterranean termites in northern California implies that there is one species, R. hesperus Banks. The diurnal flights of R. hesperus are reported to occur in the spring and early fall. The fall flights are very conspicuous, with thousands of alates emerging from many colonies simultaneously. Spring flights are relatively diffuse and usually follow periods of rainfall on clear, sunny afternoons. Recent chemosystematic studies of Reticulitermes indicate at least 4 cuticular hydrocarbon phenotypes occurring in northern California. Characterization of the soldier defense secretions of these phenotypes corroborates their status as distinct taxa. The three most common phenotypes, CA-A, CA-A' and CA-D, are sympatric in the San Francisco Bay Area. Since the spring of 1994, we have been able to collect alates from our monitoring stations, from laboratory cultures, and during flights in neighborhoods in the greater San Francisco Bay Area. After collection, the cuticular hydrocarbons of alates were characterized by gas chromatography/mass spectrometry. As predicted, over the past 7 years there were two flight seasons: one from early February to early May and one from early October through mid December. The flights in the spring produced only phenotypes CA-A and CA-A'; those in the fall exclusively included phenotype CA-D. These disparate flight times provide a reproductive isolating mechanism and are further evidence that phenotypes CA-A and CA-A' constitute a taxon distinct from CA-D. This information, along with supporting data on distinct cuticular hydrocarbon and soldier defense secretion profiles and agonistic behavior toward opposite phenotypes, convinces us that CA-A/A' and CA-D represent different species and that R. hesperus coexists with another species over much of its distribution. In the near future we need to confirm this hypothesis with genetic analyses and morphological descriptions.
Species 1: Isoptera Rhinotermitidae Reticulitermes (western subterranean termite)
Keywords: speciation, insect flight
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