X-Message-Number: 13068
Date: Fri, 7 Jan 2000 07:11:04 -0800 (PST)
From: Doug Skrecky <>
Subject: cold hardening flies

  Rosales AL.  Krafsur ES.  Kim Y.
  Department of Entomology, Iowa State University, Ames 50011.
  Cryobiology of the face fly and house fly (Diptera:
  Journal of Medical Entomology.  31(5):671-80, 1994 Sep.
  Face flies, Musca autumnalis De Geer, have a circumpolar distribution and
  overwinter as adults in reproductive diapause. House flies, Musca domestica
  L., have a cosmopolitan distribution and overwinter in northern latitudes in
  animal confinement quarters. We compared supercooling points with low
  temperature tolerances, as measured by bioassays, in all developmental stages
  of both species. There was no correlation between supercooling points and the
  ability to survive subzero temperatures. Rapid cold hardening was induced in
  adults of both species by a 2-h acclimation period at 0 degrees C. Hemolymph
  melting points were measured osmometrically in diapausing and reproductive
  face flies. Freezing point depressions differed between diapausing and
  reproductive flies and between reproductive flies given a 2-h pre-exposure to
  0 degrees C and unexposed flies. Our data suggest that a -8 to 8 degrees C
  range with a mean close to 0 degrees C is necessary for successful face fly
  overwintering. House fly overwintering sites must offer microhabitats that
  remain above -5 degrees C with sufficient time above 10 degrees C to allow
  larval, pupal, and ovarian development.

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