The small forest caterpillar hunter also plays a role; we are seeing numbers increase gradually and will monitor the situation. The small forest caterpillar hunter is a slightly smaller beetle which lives in the same biotope and probably benefits from the more favourable conditions created by climate change. Observations tend to be made in May and June, with a peak in May. They principally eat winter moths but when the oak processionary caterpillars are small (they grow quickly in May), they can serve as a food source.