3.5cm sand dune caterpillar?

3.5cm sand dune caterpillar?

Observation - 3.5cm sand dune caterpillar? - UK and Ireland. Description: 3.5cm moth caterpillar found on grass in sand dunes, south east Ireland. The brown line on the back may help ID, so far I havent found a match in ukleps and Ive looked virtually everything there. Any help much appreciated.

3.5cm moth caterpillar found on grass in sand dunes, south east Ireland. The brown line on the back may help ID, so far I havent found a match in ukleps and Ive looked virtually everything there. Any help much appreciated.