From Calais/Boulene drive south on the A16 & come off at Exit 24.

Pick up the N1 south to NOUVION (about 2 mites) Turn RIGHT & pick up a minor road to Bonelle, this is just north of Sailly Bray. Through Bonelle a tiny hamlet turn left NOT straight on to Ponthoile. Now on a farm track but perfectly drivable with a marsh on your see and arable on a slight rise to your right.

Swallowtail's have been seen on the marsh and the Map butterfly towards the end of the track, near the first building on the LEFT of the track.

While in the area you should visit Crecy Forest, Large Tortoiseshell's & Purple Emperor's. Also the Parc ornithologique du Marquenterre which is the coast west of Crotoy, well signposted.

This whole area is superb for birds and no doubt could turn up some interesting butterflies particularly in the Forest. The motorway journey takes abut 75 minutes or a little less.

Allow 75 minutes on the return trip to the ferry at Calais.