New Article! Climate Change and the Large White
Posted: Tue Feb 24, 2015 12:23 am
Hi Pete,
I have little doubt that Nick's thesis holds water.
Here is a posting I made to the BC Sussex website on 21st November 2008, made in response to the observation of high survival rate amongst high numbers of Large White caterpillars, by one of our members, Bob Brown, on his Seaford allotment:
"I was interested to hear Bob Brown's account of abundant Large White caterpillars on his local allotments in Seaford. This is really very late for the caterpillars, which are the progeny of a late season influx of immigrant butterflies from the Continent (large numbers were reported from coastal areas, including towns and cities such as Brighton & Hove). This species will happily survive the UK winter as a chrysalis. Whether these caterpillars manage to reach the point of pupation will largely depend on how advanced they currently are, relative to the remaining food supply and weather conditions over the next week or two. The main parasite of the species (the wasp Apanteles glomeratus, which forms the characteristic yellow clusters of its own pupae around the caterpillar corpses) will not have been around to decimate the caterpillar numbers this late in the year. Hence the survival rate will be unusually high for this batch of larvae."
It became clear that many of these caterpillars pupated successfully, as reported by Bob Brown in a later post, dated 1st December 2008:
"Sadly illness and weather prevented my return to the Seaford allotments until today to check the fate of the Large White caterpillars, when there was weak sunshine and bitter cold. A very few of the caterpillars are still on the cabbages etc., but most have disappeared. One of the neighbouring allotment-holders with a brand new shed and untouched young cabbage plants told me he had seen some caterpillars crossing over to his allotment, and they had got inside his new shed. They had then climbed up to at least 6 feet off the ground, before suspending themselves to prepare to pupate. How do they work that out? He wont give them chance though, they will be squijed in due course! "
Large White caterpillars were still active (just!) in Sussex, as the year drew to a close, as reported by Sam Bayley on 30th December 2008, who had monitored their progress on broccoli in his Warnham garden:
"A quick check of my broccoli plant in the garden this morning and there were still at least 20 Large White caterpillars in situ. They are all now in their 3rd instar with many shed skins still visible and in minus temperatures they were moving very slowly and I did find a couple that had died."
BWs, Neil