Yponomeuta species
Larvae are small, blackish-yellow with dark spots and are hairless.
The webbing (above right) produced in spring and early summer can be extensive and drape over entire trees or lengths of hedgerow, which may be completely defoliated.
There are eight very similar UK species which feed on separate host-plants (typically cherry, hawthorn, blackthorn, spindle, willow & sallow), but none are known to feed on oak.