Friday, May 11, 2012

Butterfly Boom Year

The most common question in the last few weeks has been "Where are all these butterflies coming from?"  Even friends whose view of nature is through a windshield have noticed the swarms along roads and gravel drives.  My guess is that the mild to non-existent winter dramatically reduced the normal cold weather mortality.  Fewer freezes means fewer dead eggs, larvae and even over-wintering adults like the Mourning Cloak.

Mourning Cloak- Chris Barnhart
Last Friday, a 100 foot stretch of gravel road east of the old red bridge was covered with 300+ butterflies.*  There was a mix of Mourning Cloak, Red Admiral, Comma and Question Marks, Zebra and Spicebush Swallowtail as well as smaller species.  They were all collecting minerals off the gravel in preparation for their next breeding.  They were so engrossed in their task that they flew off only when we crept by in the truck, then immediately swarmed back to the same spot.

Mourning Cloak Caterpillars
Mourning Cloaks over-winter as adults and start laying eggs immediately.  That hatch breeds again, and the second batch emerges as butterflies prepared to face the winter.  They nestle under bark, treasuring our shagbark hickory and other loose barked trees.  On a warm winter day you will see one go fluttering by, catching some rays while it can.

In a normal year, I will see Mourning Cloaks infrequently, but this spring they are almost as common as other dark butterflies such as Spicebush and Pipevine Swallowtails.  It will be interesting to see what happens to these abundant populations later this summer.  If nature balances as usual, we may see fat birds and an increase in the tiny wasps which lay their eggs on caterpillars.

Caterpillars drop when startled
Two weeks ago we were out hunting caterpillars and found these beautiful Mourning Cloak caterpillars, decimating the leaves on a dwarf hackberry.  Like many cats, their defense mechanism when disturbed is to drop to the ground.  Normally this is a good strategy but when there is a waiting net below, not so good.  I am happy to report that they will eclose (emerge from the chrysalis) in a better place with lots of loving kids to watch.

Tom Riley reports observations on the early migration of southern species in the FOG News Blog.  Not only are they arriving early but some species are now breeding farther north as might be expected with the warming temperatures.  Who knows, some day we may be advertising "Ozarks- the new Costa Rica."

*  How do you count 300 butterflies?  I learned this trick from our Master Naturalist Buck Keagy.  You count their antennae and divide by two.

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