The caterpillar is dingy grey or greenish, with a row of black spots down the back, and a whitish stripe on each side. It feeds on the common sorrel (Rumex acetosa) and the sheep sorrel (R. acetosella), and when fully grown it spins a cocoon on the stem of its food plant, and there changes to a chrysalis.
The larva may be found during May and early June. The chrysalis state lasts only a few days, and the moth is on the wing during June and July.
The Broad-bordered Five-spotted Burnet (Zygæna Trifolii)
On [Plate IX] (fig. 7) will be found a coloured representation of this Burnet. The two crimson spots in the base of the fore wing are very close together, and often touch. The same remark also applies to the two spots on the middle of the wing. A glance at the list of British Moths (Appendix I) will show that we have also a Narrow-bordered Five-spotted Burnet. This insect is very similar to the species now under consideration, but may be identified by the narrower purplish margin on the hind wings, and also by the shape of the antennæ, which are not thickened so much near the end as they are in Trifolii.
The larva of the present species is yellowish or greenish, with a row of black spots on the back and a row on each side. It feeds on the bird's-foot trefoil (Lotus corniculatus), hop trefoil (Trifolium procumbens), and the horse-shoe vetch (Hippocrepis comosa) in May. Late in May or in early June the chrysalis may be found in a silken cocoon attached to a stem or leaf; and the perfect insect flies during June and July.
The Six-spotted Burnet (Zygæna Filipendulæ)
So common is this moth, and so conspicuous when it flies in the blazing sun, that it must be familiar to almost everybody. On a bright midsummer day hundreds may often be started from their grassy beds from one little patch of ground.