Sunday, June 24, 2012

Butterfly Blues

We met this and several more clusters of blue butterflies today, mud-puddling (them) along the Madison River (us), just downstream from Ennis Lake. They are probably some species of Blues (duh), but that's about as deep as I can get in my best butterfly book ("Butterflies Through Binoculars, the West"). The author, Jeffrey Glassberg, confirms my difficulties when describing the similar-looking Blues as, "...complex ... frustratingly difficult to understand."

Mud-puddling blue butterflies
(c) John Ashley
Blueish butterflies puddling for nutrients in wet soil.
The dot patterns on the underwings don't look like an Arrowhead Blue or Silvery Blue, nor Boisduval's Blue, Greenish Blue, Acmon Blue or Arctic Blue - all of which occur in western Montana. The underwings do resemble the Northern Blue (Lycaeides idas) photos in this book. But these guys look like the photos for Northern Blues from Washington, not the Northern Blues from Montana. Sigh. Glassberg was right, this is frustrating.

Puddling is an interesting behavior of moths and butterflies. The hypotheses for this behavior fall into two broad categories: puddling to obtain some scarce mineral (e.g. sodium, ammonium, sugars), and puddling by young individuals (especially males) that are excluded from better food sources (e.g. flower nectar) by older butterflies (especially females).

In most puddling species, it is mostly the males who puddle to collect sodium ions. In these species, the total sodium needs for egg production exceeds the amount of sodium that the female alone can provide. The extra sodium obtained by a puddling male is transferred to her during mating, included in his spermatophore.

So the puddling butterflies above might be a "flutter" of male Northern Blues, gathering sodium for their future mates to increase the survival of their eggs. Or then again, maybe not.