Thursday Blue Butterfly

Puddling Silvery Blue

It's always nice when an insect lives up to its name and the small blue butterflies now common around fields with Wild Vetch and Creamy Pea Vine are called Silvery Blues Glaucopsyche lygdamus (Doubleday, 1841). The males are more silvery and, perhaps, more likely to be seen, since they patrol the areas around the plants that their caterpillars would like to eat.

Silvery Blue exposed

The reason that butterflies, and especially male butterflies, may be found sipping mud rather than flowers (a behaviour called: puddling) is a bit obscure, but seems to be somewhat similar to taking vitamin pills in humans. Essential nutrients and salts not overabundant in the larval food, mostly plants, may be present in wet soil or less savory (to us) wet organic substrates. Males have a hard life flying back and forth, chasing away other males, and chasing females, so a puddle of mud may be a pleasant and invigorating break.

Silvery Blues are grey and spotted underneath

The reason for the often striking differences between the upper and lower wing surfaces of many butterflies is a bit obscure too, but one reason is most likely obscurity. It is easier to blend into a background when not boldly coloured, especially if the colour can suddenly disappear with the fold of the wings. Flashing the upper colours may also be useful to startle enemies, tell other males to get lost, and advertise one's beauty to the opposite sex.

Nectering is good for the vetch, but leaving behind eggs, maybe not so good

Energy for all the fluttering activity comes mostly from nectar and the butterflies may pay the plants back for their sugary rewards by transferring pollen. However, this Wild Vetch might much rather be pollinated by one of the bumble bees or carpenter bees that also were visiting, because the larvae of the Silvery Blue feed on assorted wild legumes such as this vetch. As the caterpillars feed they secrete a sugary substance that is very attractive to ants. The ants become addicted to their tasty reward and vigorously defend the larvae against other insects, including parasitoids. That seems a pretty exceptional life history, but if you look closely enough at any insect and you are likely to find equally unexpected and fascinating stories.