Winter moths

Operophtera brumata

Often overlooked as drab, nocturnal butterflies, I think moths are much more interesting than they're given credit for; from micro moths to macro-moths, the variety in these group is astounding. In the British Isles, over 2500 moth species have been recorded, which although impressive, pales in comparison to the estimated 160,000 species globally. 

One moth that can be seen flying at this time of year is the Winter moth (Operophtera brumata), which I spotted this week in the woodland on the UEA campus. This moth is able to cope with freezing temperatures and flies from late autumn to late January/early February. In this period mating occurs; the females (which have extremely reduced wings) rest on trees and release pheromones to attract the flying males. Once fertilised, eggs are laid on twigs and bark to overwinter. The eggs then hatch in spring into pale green caterpillars to feed on foliage. One notable feature of the caterpillars is the ability to use a silken thread to catch the wind and carry them to another food source. Oak and apple are the preferred food of the caterpillars, although they will feed on a variety of tree species, such as beach, pear and willow. When present in large numbers, the larvae have been known to completely defoliate small trees. Around June the larvae drop to the ground and pupate in the top layer of soil, to emerge again as adult moths around October. 


Native to north and central Europe, the Winter moth is a common resident species across the UK. These moths have an important role to play in the ecosystem - great tits and blue tits feed winter moth caterpillars to their young in Spring, and time their breeding to match the moth life cycle. However, in the US it's a different story - winter moths are an invasive species in North America, and can cause damage to agricultural crops and trees. A parasitic fly (Cyzenis albicans) specific to winter moths have been introduced to help control the moth population. Another mitigation method is not moving plants or soil from infested areas. 

Although currently a common species, one possible threat to winter moths is the changes in temperature patterns due to climate change. These changes could disrupt the phenology of the moths and the bud burst of their larval food plants. This would cause problems for winter moths as if the larvae emerge too early there will be insufficient food, leading to starvation; if they emerge too late, the leaves of food plants are higher in tannins and less digestible, causing a lower body mass at pupation or a longer larval period, increasing the chance of predation or parasitism. One study (Visser and Holleman, 2001) showed winter moth eggs hatching up to 3 weeks before the oak bud burst in recent warmer springs. 

                                                                                    Winter moth taxonomy

Lepidoptera and their roles in ecosystems are something I would definitely like to learn more about and as a student ecologist, moths are a perfect species to look for - we are currently both nocturnal!

https://ukmoths.org.uk/species/operophtera-brumata/
https://butterfly-conservation.org/moths/winter-moth
https://www.norfolkmoths.co.uk/?bf=17990
https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2000.1363 

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