Fauna of the Week--Monarch Butterfly
This week's Fauna of the Week was probably a forgone conclusion given this week's Flora...hate to disappoint!
The Monarch Butterfly is notorious because of its long migration (up to 2500 miles) to sites primarily in Southern California and Mexico for overwintering. Survivors then attempt to return from their birth places, which range from Southern Canada to South America. It is a large, striking butterfly and has the habit of winging more slowly than many. No doubt this is because it knows it tastes nasty and is gloating.
This nastiness is the result of ingesting (with no ill effects) cardiac glycosides found in the milkweed plants it consumes as a sweet young thing. Cardiac Glycosides are found in plenty of other plants--most notably foxgloves and oleander--and the milkweeds are far from being the strongest concentrations out there. Regardless, if the concentrations in milkweeds can make people sick to the stomach, I'm sure it's much worse for the birds who overzealously try to eat a monarch. Hence their laziness in flight. I personally appreciate this laziness, since it makes them easier to photograph! (Pictured at left, monarch caterpillar pausing in its consumption of cardiac glycosides. Caterpillar poop evident on stem of plant to left. Don't eat that, either. Just sayin'.)
Earlier this summer, monarchs were sipping from Joe-Pye Weed and liatris, but have since moved on to goldenrod and ironweed. Like other butterflies, they will use multiple sources of nectar. When the milkweeds are in bloom, they will most certainly use them as nectar sources, as well as a place to lay their eggs.
Monarchs go through a series of "generations" in a summer. There is the group that arrives from overwintering. They lay eggs and then die. There is that batch of eggs, which transforms from the larval stage to adults, lives two to six weeks and then dies. They lay more eggs after maturity, of course--that third generation does exactly as the second generation did, dying between two and six weeks after maturing into adult butterflies. The last generation, which around here is currently devouring my milkweed, is the group which will migrate for overwintering. I'd better feed them well!