Ermine moths are usually white or pale grey with many dark speckles, hence the name. The larvae make spectacular and ghostly communal web like nests for protection, allowing them to gorge on trees, sometimes stripping them bare. The trees may survive, though with reduced growth in the following season. The caterpillars covering the trees here at the Nine Wells may be those of the bird cherry ermine moth (Yponomeuta evonymella). The obelisk was erected in 1861 to mark the exploitation of the Wells as a freshwater supply for Cambridge 400 years ago.
Photo: Nine Wells, Cambridge, May 2004