Friday, June 29, 2012

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.


  1. There's a little grassy clearing where some paths cross in the woods that I call the "bee-loud glade;" it is lined with wildflowers, including roses and wild vetch and the blue butterflies are all over in there. I always wanted to know more about them. Love learning about the "puddling." :)

  2. Not sure if albino earwigs are a common thing, but thought you might want to see a picture of one taken by a gardener:

    I can honestly say I'm not sure I wanted to see it....bleck! :)

    1. The earwig looks like a recently moulted adult, so not really an albino. Insects have their skeletons on the outside of their bodies and to grow must form a new skin under their old skin and then cast off the old. Sometimes when I look in the mirror I wish I could do that.

      I guess you could think of most insects as serial albinos: each time they cast off their skin, they crawl out as a new, soft-bodied and usually white creature. As they inflate their bodies to their new size and harden-off their cuticle, the colours return.

  3. Of course! I never thought of insects as moulting. (Yes, wouldn't it be nice...) :)