|small white (Pieris rapae) caterpillar|
|small white caterpillar|
|woad (Isatis tinctoria)|
I got to the bottom of what was eating the recently planted woad, when I spotted five caterpillars of the small white butterfly hugging the central ribs of its leaves. The woad needs to grow on before I am happy to sacrifice it for butterfly food, so the caterpillars were removed to a suitable plant nearby.
Note the yellow dorsal stripe, and the two small yellow dots on each segment of the caterpillar, which distinguishes it from the similar green-veined white (Pieris napi) caterpillar.
Caterpillar ID was achieved using Lewington, R., 2003 Pocket Guide to the Butterflies of Great Britain and Ireland British Wildlife Publishing, Dorset