The Alcon blue The Alcon blue butterfly (Maculinea alcon) can be seen flying in mid to late summer. In Denmark it is on the wing during the month of July.

The Alcon blue is a member of the family of butterflies called the Lycaenidae. This family includes the blues, coppers and hairstreaks. The lycaenidae is one of the largest butterfly families. One reason for the success of this family of butterflies is that their caterpillars and pupae often have some sort of association with ants. Most of the lycaenidae that associate with ants have a mutualistic relationship with them. However the Alcon blue and other large blue butterflies (butterflies in the genus Maculinea) are parasites of ant colonies. The picture on the right shows a male Alcon blue sunning himself on a cloudy day in Denmark.

The female Alcon blue (left) generally has more prominent black spots on, and a broader black border to her wings, but this is quite variable. Little is known of how Alcon blues find and choose their mates. Male Alcon blues emerge slightly earlier in the year than females, and males can often be seen flying backward and forward over areas with ant nests from which females may emerge. It is quite common to see mating pairs where the female has not finished expanding her wings, so it is likely that females are often mated soon after they emerge, and have little opportunity to assess and choose particular mates

Both sexes have underwings with a distinctive pattern of black spots. The Alcon blue, like all the large blue butterflies, is rare. It is classified as endangered or vulnerable to extinction on most countries in western Europe. Luckily the populations in Denmark are healthier than most of those in the rest of Europe.