Five Insects Believed to be Newly Established or Recolonized on Santa Cruz Island, California (Dermaptera, Lepidoptera)

Abstract

An earwig, 2 moths, and 2 butterflies not recorded in 1939^1 and 1966-69 surveys of S.C.I, insects, became established during 1969-78. Evidence suggests that 3 were introduced by man. Sudden appearance of the butterflies, however, is not easily interpreted. Either might have immigrated often during 50-100 years S.C.I, has had their weedy hostplants. It is hypothesized that such species periodically colonize, are eliminated during stress such as overgrazing by feral sheep in drought years, then recolonize. An undersaturated nature of the insect fauna of offshore islands, especially badly perturbed ones, is proposed. Extinction presumably is higher than natural, immigration low, and/or colonization improbable owing to reduced patch sizes of native hostplants.