Survival at low temperature of larvae of the pine processionary moth Thaumetopoea pityocampa from an area of range expansion |
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Authors: | Gernot Hoch Edoardo Petrucco Toffolo Sigrid Netherer rea Battisti and Axel Schopf |
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Affiliation: | Department of Forest and Soil Sciences, BOKU University of Natural Resources and Applied Life Sciences, Hasenauerstrasse 38, 1190 Vienna, Austria and Department of Environmental Agronomy-Entomology, University of Padova, Via Università16a, 35020 Legnaro, Italy |
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Abstract: | 1 Larvae of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) develop throughout the winter, although their feeding activity and survival can be impaired by adverse climatic factors. The present study investigated the survival at low temperature of larvae originating from a population with range expansion in an alpine valley in Northern Italy. 2 The supercooling point of individually analysed larvae averaged at −7 °C. This value insufficiently described the cold hardiness of the larvae; 39% of the tested larvae were alive when returned to room temperature immediately after freezing. When larval colonies inside their nest were exposed to −17 °C for 1 h after gradual temperature decrease, survival was 70.4%. 3 Rearing of larvae in the laboratory at different day/night temperatures indicated an effect of cumulative chill injury on larvae. A logistic regression explained the relationship between negative thermal sum (h°C below 0 °C) received in the laboratory experiment and larval survival. A similar relationship was demonstrated between negative thermal sum and survival of larval colonies in the field. 4 In the laboratory experiment, some tested larvae were able to survive for up to 8 weeks without feeding depending on rearing temperature. As expected, feeding occurred only when larvae were reared at temperatures of 9 °C day/0 °C night. 5 We classify the larvae of T. pityocampa as being moderate freezing tolerant. The winter behaviour allows this species to track climate warming by a rapid expansion into those areas that become compatible with the insect's development. |
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Keywords: | Chill injury cold hardiness freeze tolerance larval survival Lepidoptera range expansion supercooling point |
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