Friday, September 12, 2014

Army of Caterpillars - Datana ministra

Now for more hungry caterpillars.  This is Datana ministra, in the same genus as the Major in the previous post.

I found this species feeding on a small Blackjack Oak, Quercus marilandica.  It was evident from quite a distance that this tree had seen caterpillar damage.  Many of the upper branches were left with nothing but stout petioles where there should have been leaves.

The caterpillars are all final instar and have spread throughout the tree.  They are numerous enough to defoliate an oak of this size.  I made a count of nearly 50 individuals and may have missed a few.

Body size and shape is nearly identical to D. major, but the coloration is not nearly as bright.  The body is basically black with several yellow lines.

This species is commonly called the Yellow-necked Caterpillar.  Yellow just behind the head along with this showy orange patch are responsible for that designation.

These caterpillars displayed an interesting feeding strategy.  A pair would team up, with members of the pair working opposite sides of the leaf.  The result is a leaf that still retains its balanced shape.  Many predators search out caterpillars by targeting irregularly shaped leaves resulting from caterpillar feeding activities.  Synchronized feeding helps hide the fact that the leaf is being consumed.

The effects were not always perfect, but the result usually looked much like a naturally formed leaf.

This pairing was not an isolated incident.  Many feeding pairs were found on the tree.

The pair would feed until there was no leaf left and then would back down the petiole and move off to another leaf.

Of course, the plan was not always executed perfectly.  When three caterpillars end up on the end of the same stalk it begins to get silly.  We should stop here before things get out of hand.

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