Effect of Sex and Age on the Supercooling Point of the Winter-Active Diamesa mendotae Muttkowski (Diptera: Chironomidae)

Author： Carrillo M.A. Cannon C.A. Ferrington Leonard

Publisher： Taylor & Francis Ltd

ISSN： 0165-0424

Source： Aquatic Insects, Vol.26, Iss.3-4, 2004-09, pp. : 243-251

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Abstract

Supercooling points (SCP) of adult Diamesa mendotae Muttkowski, 1915 (Diptera: Chironomidae) were determined at 3, 5, 9, 12 and 17 days post-collection. Supercooling points were recorded using surface contact thermometry and a cooling rate of ca . 1°C min −1 . Female SCPs averaged −22.81, −23.76, −23.85, −23.65, and −20.87°C on each date post-collection and did not differ significantly. Male SCPs were statistically similar and averaged −21.75, −23.53, −23.68, −23.66, and −22.92°C on each date post-collection. Paired comparisons of female/male SCPs on each date post-collection did not show significant differences over time. The overall mean SCP of D. mendotae (−23.05°C) is substantially lower than values of −5.3°C and −5.7°C published for adults and larvae of Belgica antarctica Jacobs 1900 collected at Palmer Station (Antarctica) and −14.2°C for larvae of Paraclunio alaskensis Coquillett 1900 collected at Vancouver Island, British Columbia. In addition, the SCP of this species appears to be lower than that of other winter-active insect species reported in the literature. Although no adults survived after the SCP was recorded, further studies are necessary to determine if D . mendotae is a freeze-intolerant insect. Nevertheless, our results suggest that a low SCP could be used as a mechanism to facilitate emergence and adult activity of this species during winter conditions.