Continuing with my Butterfly theme this one is also on the wing now until the end of July.
You can tell a Large Skipper from a Small or Essex Skipper by the blotchy pattern on their wings (normally referred to as chequered) the other two species have uniform orange wings. Also the antennae of the large Skipper are pointed and hooked and the others are not.
The male large Skipper, pictured below, has a prominent “sex brand”, The black, diagonal line about half way down it’s fore wing, these are actually scent scales that make it smell like a man butterfly. Also the underside of the antennae tip is orange.