The Oak Eggar (wingspan of 45 – 75mm), despite its name, does not feed on Oak, but is so-called because the shape of its chrysalis resembles that of an acorn. The food plants are mainly heather and bilberry, but also include bramble sallow, broom, sloe, hawthorn and hazel. They are often confused with butterflies but their flight is fast with sharp changes in direction as they sweep low, back and forth, tasting the air, over the vegetation in which females that have emerged the night before, are resting. Male Oak Eggars are most often seen flying on sunny afternoons while the females fly early in the evening. Once a female has been found the male will mate with her and then move on to find another female. Egg laying for an Oak Eggar moth is a fairly random affair – sometimes, she simply drops the eggs (2mm in diameter) onto the ground whilst flying around and in some cases she will release them in a cluster in one location. The larvae of the Oak Eggar moth can grow up to 6.5cm long. They are dark brown with a line of white spots along their flanks and sometimes a row of red markings is visible lower down. The hairs grow in tufts and act as a defence against predation since they can cause skin irritation, but they are still eaten by some specialists such as the cuckoo. It can take up to 2 years for the full life cycle depending on the warmth of the climate.
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