Can you spot the nest?

From the usual images of big, black peacock caterpillars, you might think that they are easy to find. But this is not always the case, particularly when they are still small.

This image was taken at one of my field sites last week (09/07/09). It's coming to the end of the season for peacock caterpillars, so I was just looking for any remaining large nests that I may have overlooked.

I noticed the frass (caterpillar faeces) on this plant, assumed it was remnants of a previous nests, but did a quick search just in case.

Lo and behold, a nest of early instar peacock caterpillars neatly secreted under the leaf.

How to find Peacock and Small Tortoiseshell caterpillars

Find a big patch of nettles:

Nettles love nutrient-rich soil, which means they are often found where sheep or cows have been grazed. The field above is land used by dog walkers, where cattle are grazed every morning, as a result there are lots of nettles!

Both Small Tortoiseshell and Peacock caterpillars like large patches (at the very least 2m²), which are on open ground, with no shading by trees.

Look for feeding damage and frass:

The early instar larvae usually feed on the top leaves of the nettles, so there will be feeding damage and remnants of a silk-like ball around the top of the stem as you can see in this photo. Also in this photo you can see the black caterpillar frass on many of the lower leaves. To the left of the image just below the thistle, you can see the skins that remain after caterpillars have moulted.

Peacock caterpillars can be found anywhere in a patch of nettles, more often in the centre. Small Tortoiseshells are usually found at the edge of a patch, on lower nettle stems (often found when I'm bending down to get something out of my bag, which has narrowly missed squashing a nest in my haste to look through the rest of the patch).