Here’s something I would never have known had I not read it in Science Daily.

Did you know that the migratory generation of monarch butterflies — the ones that fly to Mexico — are darker red than the earlier, more sedentary generations?  The monarchs you’re seeing right now are less red than the ones you’ll see in late August.

You’re probably aware of this color difference if you raise and tag monarchs as Marcy Cunkelman does, but do you know why the last generation is darker?  Scientists are on the verge of finding out.

According to Science Daily and PLoS ONE:  Recent research, led by Andrew Davis of the University of Georgia, tested 121 captive monarchs in an apparatus called a tethered flight mill where they quantified butterfly flight speed, duration, and distance.  They found that monarchs with darker orange wings overall flew longer distances than those with lighter wings.  This suggested that pigment deposition during metamorphosis is linked with flight skill traits such as thorax muscle size, energy storage or metabolism.

It makes sense to me that a bug that has to fly to Mexico is born with the traits necessary to do the job, and it’s not too amazing that dark color is one of them.  In birds, dark feathers are stronger than light-colored feathers.  Perhaps this applies to the wing scales of butterflies, too.

For a picture of these color differences, see the Science Daily article here and the original article at PLoS ONE.

Meanwhile, if you have a butterfly net and a camera you can do some research on your own.  Look for monarchs now and again at the end of the month. When your photographs record darker red monarchs in late August, you’ll know why.

(photo of a monarch butterfly by Marcy Cunkelman)