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Wednesday, March 09, 2011

Is March Caterpillar Madness Imminent?

We found a cache of dark barrel-shaped insect poop on the front porch steps today.  There was no sign on the nearby plants of grasshoppers or caterpillars; nor evidence of their recent chewings there.  So the eye continues upward, past the acacia, past the eaves, past the power lines up into the freshly foliated Ulmus parvifolia tree.  Up there are several large and a few scattered bunches of dark possibly spiky caterpillar shapes, sure to be the larvae of Nymphalis antiopa, the mourning cloak butterfly.  Elm, along with other trees such as willow, birch and poplar, is larval food for this species.  The female butterflies lay clusters of eggs on the tree twigs.  After hatching, the caterpillars feed as a happy hungry group.

I guess there are about 30 or so large caterpillars on three or four elm branches that just happen to overhang the porch steps.  A few wasps were cruising the airspace around them, seeking easy prey.  I expect the survivors will soon march out of the tree, as they usually do this time of year, seeking a vertical surface (often the side of my house, sometimes the elm tree trunk) on which to pupate.

The caterpillars consumed all the leaves from a few branches of the tree; a smallish price to pay for butterflies.

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