Isometopinae (Hemiptera: Miridae) in Pennsylvania: Biology and Descriptions of Fifth Instars, with Observations of Predation on Obscure Scale

Abstract

Four species of isometopine mirids were studied in central Pennsylvania during 1976–77: Corticoris pulchellus (Heidemann), C. signatus (Heidemann), Diphleps unica Bergroth, and Myiomma cixiiformis (Uhler). Descriptions, illustrations, and a key are provided for the last instars. Seasonal history of all species is given, and more detailed field and laboratory observations are presented for C. signatus and M. cixiiformis, which prey on obscure scale, Melanaspis obscura (Comstock), infesting trunks of pin oaks. Eggs of both species are deposited under old female scale covers, and overwintered eggs begin to hatch in mid-April. Adults begin to mature during late May-early June. M. cixiiformis (and also C. pulchellus and D. unica) is univoltine but C. signatus has a 2nd generation during mid-summer. In the laboratory nymphs and adults of both species probed female scales and fed by curving the proboscis under the covers. These observations of predation on scale insects and oviposition are the 1st documented habits of any North American isometopid. The Isometopinae are regarded as the most plesiomorphic mirid subfamily; if the predatory habit is also assumed to be plesiomorphic, then discovery of scale predation by 2 species supports placement of the isometopines as the sister group of all other Miridae.