A knot grass moth caterpillar photographed in England in June

by | Published | Last updated

A caterpillar of a knot grass moth (Acronicta rumicis) exploring the top of a creeping thistle in the countryside in England, 11 June 2022. Most of the caterpillar's body is black, with tufts of light brown hairs. Seen here is the undulating single stripe of alternate red and yellow along its side. Each red part of this stripe protrudes from the body and from it sprouts a tuft of hairs. Above each red protrusion is a small white dot.

The photographs here show a caterpillar of the knot grass moth (Acronicta rumicis) as found feeding on creeping thistles (Cirsium arvense) in the English countryside in June 2022. Most of the caterpillar's body was black, with tufts of light brown hairs, two lines of white blotches along its back and a wavy stripe of alternate red and yellow along each side, Close to this stripe were small white points. Each alternation of red and yellow and each white point corresponded to one segment of the caterpillar. It was about 30mm long.

The last photograph shows the immediate environment of the caterpillar, a patch of creeping thistles and grass. It remained on the same thistle or a nearby thistle less than 50cm away over the course of a week while I revisited it.

This caterpillar sometimes made itself quite conspicuous, remaining on top of the leaves of the thistle or climbing up and down the plant, and only sometimes clinging to the underside of a leaf. On revisiting on multiple days I was usually able to spot it again within about thirty seconds.

Despite the conspicuousness of this caterpillar, repeated cursory surveys of the patch of thistles did not find another one.

The same knot grass moth caterpillar in further explorations of the creeping thistle in the countryside in England, 11 June 2022. Visible in this side view are three pairs of front legs, four pairs of proto-legs and at the rear the pair of claspers which it is using to hold on to the leaf on the right.
View of the back of the same knot grass moth caterpillar showing two parallel lines of small, irregular-shaped white blotches and between them smaller specks of yellow and orange along the centre line, while most of the caterpillar is black, with tufts of brown hairs. England, 15 June 2022
The knot grass caterpillar was about 3cm long. Here a centimetre ruler is held next to it. England, 15 June 2022.
The patch of creeping thistles where the knot grass moth caterpillar was found in the countryside in England, 11 June 2022. Although this caterpillar was often conspicuous, repeated cursory scans of this thistle patch did not reveal another one.

Related