Rose Sawfly Larvae- these 15mm munchers look superficially like caterpillars but they are one of 8,000 Sawfly species worldwide, named after the saw-shaped ovipositor of the females, with which they cut a slot in the host plant in which to deposit their eggs.sHarmless, except when in such numbers that they defoliate whole plants (which then recover), the larvae go through eight different developmental stages. Caterpillars never have more than five pairs of legs but Sawfly larvae have six or more. Sawfly larvae often feed on gregariously, like these, and when threatened take this classic ‘S’ shape. Conditions: Sun and cloud. Dry again. Temperature: Max 24 Min 13C.