No, this pair of twins are not late for the migration. They are a type of Poles Dragons, they migrate from the south to north pole. This type of dragon can be recognized by their blue eyes. The blue eyes are said to see better at night because they have more rods and cones. Rods can see black and white, while the cones can see color.
These are called Tree Moss Dragons, due to their greenish color.
The dragons were tatted with 2 strands of rayon sewing thread.
This pattern can be found on Craftree, by Michelle Bottosff.