Spring emergence of CanadianDelia radicumand synchronization with its natural enemy,Aleochara bilineata

Abstract

AbstractTo characterize time of spring emergence following post-diapause development,Delia radicum(L.) (Diptera: Anthomyiidae) from Saskatchewan, Manitoba, and southwestern Ontario were collected in fall, maintained over winter at 1 °C, then transferred to higher constant temperatures until adult emergence. At each location there were “early” and “late” phenotypes. Truncated normal models of temperature dependency of development rate were fitted for each phenotype from each location. We provide the first evidence of geographic variation in the criteria separating these phenotypes. Separation criteria and models for early and late phenotypes at the two prairie locations, approximately 700 km apart, were indistinguishable, but differed from those for Ontario. Prairie phenotypes developed more slowly than Ontario phenotypes, and more prairie individuals were of the late phenotype. Poor synchronization of spring emergence could impair predation ofD. radicumeggs by adultAleochara bilineataGyllenhal (Coleoptera: Staphylinidae).Aleochara bilineatafrom Manitoba were reared and development rates modelled as forD. radicum. Models of development rates for the two species, when combined with simulated soil temperatures for two prairie locations, suggest that emergence of adultA. bilineatais well synchronized with availability ofD. radicumeggs in prairie canola.