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Colias myrmidone

Danube Clouded Yellow

euroButterflies

by Matt Rowlings

Cluj, Romania, May 2009

Cluj, Romania, May 2009

Female

Field notes and information

This is now a very rare butterfly. In flight the male is reddish and the female has very exensive bright patches in the hindwing border which helps separate it from other Colias. It has declined massively in the last two or three decades having been lost from Germany, Czeck Republis and probably Poland, Slovakia and Hungary. Its stronghold now being Romania where it survives on grasslands where light grazing encourages the growth of the larval food plant.

Identification & Similar species: The male upperside is a rich orange, distinctive even in flight compared to the similar clouded yellow, C. croceus. The female has a very extensive band of yellow submarginal spots on the upper hindwing.

Very similar to the Balkan clouded yellow, C. caucasica. Ranges do not overlap, although they are close in, for example, Serbia.

Distribution & Flight: Formerly Eastern Europe eastwards from southeast Germany. Now confined to Romania with possibly a few colonies in Slovakia, Hungary and eastern Poland. Flies eastwards through Russia and neighbouring countries.

This decline is often attributed to changing land use as grassland habitat has to be lightly grazed to get just the right grass length for the food plant. Too much/ too little grazing and the habitat becomes unsuitable.

There are usually two broods a year, late May/ early June and the end of August.

Habitat & Behaviour: Dry hillsides with open flowery grassland usually amongst open scrub. The food plant Cytisus sp. thrives in low but not short grassland and is often common where found.

It has a powerful flight. Males will patrol a certain flight path (see photos) presumably hoping to intercept females. It is reported that males will wander, occasionally being found at large distances from known habitats.