Species of the Month - August 2017

Broom Moth caterpillar

Ceramica pisi (formerly Melanchra pisi)
 

Broom Moth caterpillars appear from mid July, when they are very small, to mid September, when they reach a size of 40-45 mm before pupating.  They are frequently seen in the daytime and feed on an extraordinary variety of plants.
 

The caterpillar comes in two colour forms, green banded with a bluish-green head, and brown-banded with a pinkish-brown head.  This does not seem age-related, and I imagine that each caterpillar keeps the same colouring through all its moults.  It would be interesting to know if there is any correlation between colouring and food-plant.  The yellow stripes are common to both colour forms.
 

Cross-leaved Heath (Erica tetralix) is a popular food-plant.  Other plants we have recorded it on include Heather, Purple Moor Grass, Sitka Spruce, Bracken, Deergrass, Dwarf Birch, Yellow Saxifrage, Devilsbit Scabious, Bog Myrtle, Soft Downy Rose, Jointed Rush, Bramble and Grass of Parnassus.  It was not seen actually feeding on the plant on each occasion, but on several of them it was, and the books list many other plants that it feeds on.  So they're never likely to go hungry.  Unless of course different genetic strains are restricted to different plants.
 

This one was found on gravel by the shore of Loch Tralaig, perhaps looking for a pupation site, as it was quite large and late in the year.  They form a cocoon within the soil and spend the winter inside it as a pupa, emerging as an adult moth from late May onwards.

Broom Moth caterpillars are most often seen in open country such as heathland and moorland.  They are not likely to be confused with any other species occuring at the same time of year.  They have just 4 fairly broad bright yellow stripes, and 3 even broader green or brown stripes.  Most other species with longitudinal stripes have some of the stripes very narrow.

Please send in your Broom Moth caterpillar sightings using the form below, or email sightings@lnhg.org.uk with the details if you prefer.  If you are not sure of the identity of your caterpillar, please send a photo to sightings@lnhg.org.uk, or put one on the LNHG Facebook page.