As we were walking up Worsham Lane at about 9pm last Friday evening we saw what we took to be a caterpillar walking across the road. It had to be rescued. We encouraged it onto a leaf for a closer look.
It was soon clear that it wasn’t a caterpillar but some sort of larva. Sue’s suggestion that it was a glowworm larva surprised me because it was so large: about an inch long and getting on for a quarter of an inch wide. However, Google Lens quickly confirmed that that was probably what it was, with final confirmation from John Tyler’s book (Glow-worms) when we got home. We were surprised, having never found one before. Although the larvae are said to glow weakly it was still too light to see any glow. We returned her to the grass verge and hoped that she would have the sense to stay there.
To judge from the descriptions in the book it was probably a female in her second year. Apparently, glowworm larvae in their second year go ‘walkabout’ in daylight in late spring, presumably to feed up on slugs and snails before pupating. Since the life cycle of a glowworm is two years from egg to adult she will have survived both a very hot dry summer and a very cold winter, which is good news.
A curious fact (we learnt from the book) is that the larvae congregate before pupating, probably to increase their chances of finding a mate. Pupation of the females takes about ten days, and a few days longer for the males who have to develop wings.
It’s nice to think that in two or three weeks from now the females will have emerged and will be starting to glow – a sight well worth going out in the late evening to see. The glowing season lasts from late-May until August. If you do see any, please report them to the UK glowworm survey using this link https://irecord.org.uk/enter-glow-worm-record. Recent sightings and reports can be found here.
And finally: how do you spell glow-worm? Glow worm, Glow-worm or Glowworm? Two dictionaries give Glow-worm with a hyphen.
John Cobb and Sue Morton 27 May 2023
WEST OXFORDSHIRE FIELD CLUB 