On a blackcurrant leaf I discovered a caterpillar with an astonishing exterior and became curious about who this might be?
Aivo Tamm from the Zoology Museum of the University of Tartu found out that the caterpillar in the photo was probably that of the alder moth, Acronicta alni.
Mati Martin (2004: 18) wrote as follows in journal Eesti Loodus (Estonian Nature): ”On alder leaves one can, with luck, find something amazing, namely the caterpillar of the alder moth (Acronicta alni). The young caterpillar reminds of bird droppings that have landed on the leaf surface and doesn’t offer any particular aesthetic pleasure, rather the opposite. However, the fully grown caterpillar - that prefers to stay on the underside of leaves - looks quite different. When it is mature (July-August) it is bluish-black, with yellow spots on the back and with very long, sparsely placed hairs that get thicker at the tip.”
The caterpillar that I found moved on the top as well as on the underside of the leaves. The caterpillar is polyphagous or all-eater; most often however it feeds on birch and alder leaves.
Sources:
Viidalepp, Jaan, Remm, Hans. Eesti liblikate määraja. – Identifier for Estonian butterflies. Tallinn: Valgus, 1996.