EXPERIMENTAL ASSESSMENT OF INTERACTIONS BETWEEN LARVAL COLEOMEGILLA-MACULATA AND COCCINELLA-SEPTEMPUNCTATA (COLEOPTERA, COCCINELLIDAE) IN-FIELD CAGES

This experimental field study examined the interactions between larvae of Coccinella septempunctata L., an introduced Palearctic species, an d Coleomegilla maculata (Degeer), a Nearctic species. The interactions were examined in 5.8-m(3) field cages enclosing potatoes infested wit h Myzus persicae (Sulzer) (Homoptera: Aphididae). Intra- and interspec ific interactions were compared by using 4 measurements: developmental time and survival from 1st instar to adult, adult weight for each coc cinellid species, and M, persicae density. No significant differences were found between intra- and interspecific treatments in C. maculata survival: 19.6 and 18.3%, in 1992 and 5.7 and 3.3%, in 1993, respectiv ely; or developmental time: 24.6 and 25.4 d in 1992 and 20.4 and 20.6 d in 1993, respectively. In 1992, no significant differences were obse rved between the intra- and interspecific treatments in C. septempunct ata survival (38.3 and 39.2%) or developmental time (20.0 and 20.5 d). In 1993, no C. septempunctata survived to adults at the relatively lo wer prey densities. Interspecific interactions between C. septempuncta ta and C. maculata larvae did not significantly affect hi. persicae de nsity, compared with densities in intraspecific cages.