The supercooling point (SCP) and lower lethal temperature (LLT 50) of male adult Diamesa mendotae Muttkowski (Diptera: Chironomidae) were determined from field-collected individuals. SCP determined using surface-contact thermometry did not differ statistically from previously reported values for a previous generation of this species. The LLT50 was determined by exposing individuals to -10, -15, -20, -25, and -30°C for one minute. Mean survivorship was 96.7, 91.2, and 71.2% for tests at -10, -15, and -20°C, respectively. Exposure to -25 and -30°C resulted in 100% mortality in all tests. Results show that males of D. mendotae are freeze-intolerant with a mean SCP of -21.6°C which is only 0.1°C lower than its linear interpolated estimated LLT50 of -21.5°C. Our results confirm that a low SCP, rather than freeze tolerance, is a mechanism that facilitates emergence and adult activity of this species during winter conditions. The implications of SCP and LLT50 with regard to life cycle dynamics are discussed.
Bibliographical noteFunding Information:
We would like to thank two anonymous reviewers for critical comments on an earlier version of this manuscript. This work was partially funded by a University of Minnesota Doctoral Dissertation Fellowship (MAC) and the Minnesota Agricultural Experiment Station.
Copyright 2008 Elsevier B.V., All rights reserved.
- Cold hardiness
- Diamesa mendotae
- Lower lethal temperature
- Supercooling point
- Winter activity