In Europe, the Large Skipper (Ochlodes sylvanus) can easily be confused with the Small Skipper (Thymelicus sylvestris) and the Essex Skipper (Thymelicus lineola).
The Large Skipper is distinguished by the light spots on the underside of the wings and, in the male, the thick black scent stripe through the center of the forewing, which is thinner in the other two.
In addition, the Large Skipper has hooks at the tips of the antennae that are very conspicuous and are not present in the Small Skipper and the Essex Skipper.

The main difference between the Small Skipper and the Essex Skipper is the color of the underside of the button at the end of the antennae.
The underside is yellow-brown in the Small Skipper, while it is black in the Essex Skipper.
The Small Skipper is further distinguished from the Essex Skipper by the two-colored underside of the forewings and in the males the scent stripe that is not parallel to the veins.

Mila 23 area, Danube Delta, Romania, 24 May 2018