Caterpillar or Worm?

I'd say caterpillar but am still looking to see just what type of moth/butterfly it could turn out to be.

 

OK I think I know what your caterpillar is now Songlim. I asked a friend and they sent me this information.

Eileen it's the larvae of a Limacodidae Moth or Slug Moth.
The larvae are typically very flattened, and instead of prolegs they have suckers. The thoracic legs are reduced, but always present and they locomote by rolling waves rather than walking with individual prolegs. They even use a lubricant, a kind of liquified silk, to locomote on.

Larvae might be confused with the similarly flattened larvae of Lycaenid butterflies, but those caterpillars have prolegs, are always longer than they are wide, and are always densely covered in short or long setae (hair-like bristles). The head is extended during feeding in the Lycaenids, but remains covered in Limacodidae.

Many Limacodidae larvae are green and fairly smooth but others have tubercles with urticating hairs and may have bright warning colours. The sting can be quite potent, causing severe pain.

The larval head is concealed under folds. First instars skeletonize the leaf (avoiding small veins and eating mostly one surface), but later instars eat the whole leaf, usually from the underside. Many species seem to feed on several genera of host plants.

Research on Limacodidae larvae in temperate forests of eastern North America has found that they prefer glabrous leaves, presumably because the trichomes of pubescent leaves interfere with their movement.
I hope this is the kind of information you required."

 

No problem Songlim - just glad we could help. :-D