Essex Skipper

• It is told from its relatives by the tip of the antennae, black underneath, a detail that requires looking at the insect almost head-on.
• It was accidentally introduced into North America around 1910, in Ontario, with a consignment of grass seed, and is now abundant across much of the continent.
• Its eggs overwinter inside the sheaths of dry grasses, which lets it travel in bales of fodder.
• It reached North America by accident around 1910, near London, Ontario, in timothy seed contaminated with its eggs, and today it is established across much of Canada and the north-eastern United States.
• It keeps spreading because the eggs travel in hay bales and modern seed-cleaning techniques fail to remove them.
• There it is a pest of timothy and cocksfoot grown for forage; the treatment threshold is set at six to eight caterpillars per 30 cm square.
• It is told apart from the very similar Thymelicus sylvestris by the antennal tip, black underneath in this species and orange in the other.
• In the United Kingdom it was not identified until 1889, and its range there is also expanding.

Habitat & environment

Meadows, verges and tall grassland of Europe and North America

Sources consulted: Butterflies and Moths of North America; Pengelly (1961), The Canadian Entomologist; Prairie Pest Monitoring Network

Best time: June and July, in tall grassland