Woolly-bear caterpillars, Gynaephora groenlandica, are
important predators on the leaf buds and young catkins of Salix spp. early in the season. Field observations have shown a strong preference for Salix arctica, and for the reproductive success as well as for vegetative growth of the willows, the number and activity of the caterpillars may be of great...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.554.8944 http://www.geog.ubc.ca/itex/PDFs/ITEXchapter9.pdf |
| Summary: | important predators on the leaf buds and young catkins of Salix spp. early in the season. Field observations have shown a strong preference for Salix arctica, and for the reproductive success as well as for vegetative growth of the willows, the number and activity of the caterpillars may be of great importance. When present in the ITEX plots, especially those with Salix spp., notes should be taken on the Salix sheets or on the sheets especially designed for Gynaephora observations. The life cycle of this moth is exceptional as it may take several years to develop from first instar larva to adult insect. In Greenland, on Disko Island, outbreaks were seen in 1978 (Kristensen, pers. comm.) and again in 1992 (Mølgaard pers. obs.), which indicates fluctuations with peak populations with 14 years interval, which is similar to the life cycle duration at Alexandra Fjord (Kukal and Kevan, 1987). During this long developmental time the larvae are exposed to parasitism, which may be as impor-tant as climate in population regulation of this high arctic insect. The caterpillars emerge early in the season and obviously they feed almost exclusively on Salix buds. A preference for male leaf buds and young male catkins has been seen, which probably adds to an explanation of the female biased distribution of the two gender in Salix arctica observed on several localities in Greenland (Christensen and Mølgaard, 1991). The caterpillars orien-tate themselves in a preferred direction, which has been related to the predominant wind (Kevan et al. 1982) or to insolation (M°lgaard, upubl.) in order to maintain optimal conditions for metabolism under basking (Kukal, 1990). Based on the potential impact the caterpillars may have on the plants in combination with the extraordinary life history of Gynaephora we consider it valuable for the ITEX activities and recommend that the woolly bear caterpillar is included as the first ‘ITEX insect’. Detailed observations over the range of ITEX sites may throw light on the feeding habit, the impact on ... |
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