A mild winter delays supercooling point elevation in freeze tolerantChymomyza amoena larvae (Diptera: Drosophilidae)

Summary Supercooling point elevation to –3.2±1.3°C among 17 freeze tolerantChymomyza amoena larvae was delayed until January, 1983 in the mild winter of 1982–83 and occurred despite particulate matter in the gut. The larval population in mid-Michigan is polymorphic for both freeze tolerant and freeze sensitive larvae. One substrate,Malus coronaria fruits, appears to be a neutral niche supporting both phenotypes in the population.Discussions with K. E. Zachariassen and J. Duman before beginning the work onC. amoena cold-hardiness were invaluable. Visits of both at Michigan State University were jointly sponsored by the Depts. of Zoology and Entomology. H. Carson suggested thatC. ameona might be breeding in endemic crabapples. G. Parmalee at MSU showed one of us (HTB) a long established thicket ofMalus coronaria. The MSU Climatology Center supplied all Lansing area weather data.