Life cycle

Egg stage

• Eggs are laid in masses or plaques about 2cm long on high branches and twigs
• Females can lay between 100-300 eggs each year
• Egg plaques are covered with greyish scales and remain on trees during the following autumn and winter.
• First stage larvae hatch from eggs in April
• Moths will lay eggs on multiple oak trees

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Instar L1 - Mid April

• Eggs will hatch just prior to bud burst;
• Caterpillars are <3cm with black heads and orange bodies;
• They feed at night and stay in the leaf buds.

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Instar L2 - Early May

• Caterpillars shed skin as food and temperature increases;
• The caterpillars remain in the extremities of branches.

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Instar L3 - Mid May

• Caterpillars are now between 10-15mm long;
• They aggregate in large groups and have started to produce toxic hairs.

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Instar L4 - End of May to Mid June

• Roughly 20-25mm;
• They start to form tents, clean and pale in colour;
• There is an accumulation of shed skin and have approximately 700,000 toxic hairs each.

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Instar L5 - June to Mid July

• Caterpillars are now much easier to identify at roughly 30mm;
• Nests are larger and covered in silk and shed skins;
• There are clear signs of feeding damage.

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Instar L6 - Late June to Late July

• Caterpillars are roughly 35mm in size;
• Large, dirty nests brown in colour from shed skins, located on trunk and scaffold limbs.

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Pupae

• At ground level with grass incorporated;
• Contains a lot of excrement and shed skins;
• Remains hazardous for many years due to hairs.

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Adult Moth

• Moths start emerging around Mid July and all will have emerged by late September;
• Moths are nocturnal and live for only three to four days and do not feed;
• Males emerge before females and can fly up to 20km (12 miles);
• Females are seldom found more than 500m from their ‘home tree’ and are attracted to the ‘scent’ of oak;
• Adult moths are not easily distinguishable from some other species.