Entomologia Experimentalis et Applicata (2011) 138, 117-127

Külli Hiiesaar, Ingrid H. Williams, Marika Mänd, Anne Luik, Katrin Jõgar, Luule Metspalu, Eha Svilponis, Angela Ploomi and Irja Kivimägi (2011)
Supercooling ability and cold hardiness of the pollen beetle Meligethes aeneus
Entomologia Experimentalis et Applicata 138 (2), 117-127
Abstract: Supercooling point (SCP) and cold-hardiness of the pollen beetle Meligethes aeneus (Fabricius) (Coleoptera: Nitidulidae) were investigated. Mature eggs from the oviduct were supercooled on average to −28.0 °C and from oilseed rape buds to −24.4 °C; first instars were supercooled to −21.0 °C and second instars to −16.8 °C. Despite their high supercooling ability, none of the eggs survived 24 h exposure to −2.5 °C. The supercooling ability of adults varied significantly among feeding and non-feeding beetles: high SCPs prevailed during the whole warm period, being about −12 °C; low values of SCP of −20 °C dominated in non-feeding beetles. In spring and autumn, beetles displayed the same acclimation efficiency: after 1 week of exposure at 2.0 °C with no access to food their SCPs were depressed equally by about 3 °C. Meligethes aeneus beetles have a different response to low temperatures depending on the season. The lowest tolerance was found in reproductively active beetles after emergence from overwintering sites; the time needed to kill 50% of individuals (Ltime₅₀) was 56.2 h at −7 °C and the lower lethal temperature needed to kill 50% (Ltemp₅₀) after 24 h exposure was −8.6 °C. Cold hardiness increased from midsummer to midwinter; Ltime₅₀ was 80 h in August, 182.8 h in September, and 418.1 h in January. Lethal temperature after 24 h exposure was −9.1 °C in August and −9.8 °C in September. In February, after diapause, the beetles started to loose their cold tolerance, and Ltemp₅₀ was slightly increased to −9.5 °C. Hibernating beetles tolerated long exposure at −7 °C well, but mortality was high after short exposure if the temperature dropped below −9 °C for 24 h. Despite the season, the beetles died at temperatures well above their mean SCP; consequently, SCP is not a suitable index for cold hardiness of M. aeneus.
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Link to article at publishers website
Database assignments for author(s): Külli Hiiesaar, Eha Kruus, Luule Metspalu, Angela Ploomi, Katrin Jõgar, Irja Kivimägi

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution
environment - cropping system/rotation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Brassicogethes aeneus