Apple Ermine Yponomeuta malinellus
This species is difficult to separate the adults from other Yponomeuta species, even by genitalia examination. Identification is most reliable if done on the basis of larval foodplant and some larval and pupal features.
Y. malinellus larvae at first mine Malus leaves, and then feed gregariously in a silken web in May and early June. The larvae vary as they grow from dark grey to yellowish grey, and the size of black spots changes. Differing larvae can be found sharing the same web. Full grown larvae vary from 18 to 25 mm.
The white cocoons are arranged neatly side by side in a web beneath a leaf or twig.
The adult has pure white forewings (sometimes with a slight grey suffusion at the centre), with black dots. The terminal cilia are normally slightly grey but can be pure white. It has a white head with white palps.
Y. malinellus is widespread in England with a few records in Scotland, Wales and Ireland. It is less common than previously, and most often found in the South. It flies in July and August, and is attracted to light.