Iolana iolas/ debilitata

Var, France, May 2006
Female with broad black borders.

Var, France, May 2006
Courting. The male on the right shows only narrow black borders.

Var, France, May 2006

Iolas Blue
Iolana iolas (Iolana debilitata)

Distribution: Sporadic across Spain, SW France, Switzerland, Italy, Balkans, Hungary and Greece.

Identification: Europe's largest blue. The underside is rather unmarked with only the post discal line of spots being of note. The upperside is a uniform blue with fine black borders in the male and broad black borders in the female.

The Moroccan populations are referred to as the Moroccan Iolas Blue, Iolana debilitata, by some authors. I have seen this butterfly but frankly I can't say it looks any different to the European butterflies. No photos unfortunately.

Flight time: May to June depending on location. In coastal France, early May. In Switzerland and N Africa end May, June.

Habitat: Colonies are usually small but individuals wander widely so the butterfly seems to be in low density. The larval food plant is Bladder Senna, Colutea arborescens. The larvae feed inside the large and distinctive developing seed pods. Colonies often at the base of hot sunny slopes which puts them in danger of exploitation by man, particularly the development of vineyards.

Behaviour: The species wanders widely from the colony or suitable foodplants. As such they are usually found in only ones or twos, unless the foodplant is located. My first experiences with the butterfly were of a huge butterfly flying extremely rapidly around a Bladder Senna plant.

The adults feed frequently on the yellow flowers of the Bladder Senna. They also use the plant in dull conditions to rest on the leaves or, in hot conditions, to shelter from the sun. Males appear to be aggressive towards one another.