by Piter Kehoma Boll
Last week I introduced the arctic willow, an unusual willow that lives as a creeping plant in the Arctic and, as I mentioned then, many species feed on this small plant. One of this species is Gynaeophora groenlandica, known as the arctic woolly bear moth.
As it is common among lepidopterans, the caterpillars of the arctic woolly bear moth feed mainly on only one species, in this case the arctic willow. But they are much more than only a caterpillar feeding on an unusual plant.
Inhabiting greenland and the islands of Canada, the arctic woolly bear moth lives in an extreme environment in which temperatures are very low during most of the year. As a result, it is unable to remain active during several months and, like many arctic species, it hibernates.
In most of the world, the caterpillar of the arctic woolly bear moth would be considered of an average size but in its environment it is a relatevely large insect. Its body is covered by soft and long hair which varies from a reddish-brown to a dark-brown color. Adults have a grayish color with a hairy abdomen.
The adults mate and lay eggs around the end of June. The eggs hatch very quickly and the small first-instar larvae start to eat on arctic willow leaves but during July the temperatures start to drop quickly and the very small larvae prepare to hibernate. They spin a silken hibernaculum, a shelter to hibernate, and enter diapause, remaining inactive until June of the next year. When the snow starts to melt, they wake up, start to feed again and molt, reaching the second instar before the end of June. Then they spin another hibernaculum and enter diapause again. This cycle continues for the next years until they reach the 8th year since they hatched.
In that year, the caterpillars molt into pupae, which develop into adults in about a week. The adults then mate, lay their eggs, the eggs hatch and new first-instar larvae restart the cycle. Hatching in late June of the first year and mating and dying in mid June of the 8th year, the arctic woolly bear moth completes its life cycle in about 7 years, but this is restricted to 3 only weeks each year. They spend more than 90% of their life as hibernating caterpillars.
It is not easy to be a moth in the cold Arctic. And the arctic woolly bear moth must not only survive the harsh winters but is always threatened by parasitoids, because we all know that those damn creatures exist everywhere.
And with such a specialized life cycle, what could happen with the arctic woolly bear moth now that the temperatures in the Arctic are rising? Will it survive what we have done with Earth’s climate?
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Morewood WD, Ring RA (1998) Revision of the life history of the High Arctic moth Gynaephora groenlandica (Wocke) (Lepidoptera: Erebidae). Canadian Journal of Zoology 76:1371–1381.
Morewood DW, Wood MD (2002) Host utilization by Exorista thula Wood (sp. nov.) and Chetogena gelida (Coquillett) (Diptera: Tachinidae), parasitoids of arctic Gynaephora species (Lepidoptera: Lymantriidae). Polar Biology 25: 575–582. doi: 10.1007/s00300-002-0382-y
Wikipedia. Gynaephora gronelandica. Available at < https://en.wikipedia.org/wiki/Gynaephora_groenlandica >. Access on February 9, 2020.
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