White-lined Hawk Moth
When I first found the caterpillar illustrated,
it was feeding with a company of caterpillars of H.
gallii on the same plants (Epilobium), and I assumed it was yet
another colour variety of the latter. But it proved to be another species, H.
lineata. The mandibles, all legs and the caudal horn are yellow in lineata.
In all forms of gallii they are either red or black.