Thursday, August 12, 2010

Ash Eaters

I came across a small Blue Ash that was playing host to a number of leaf eaters. Parts of the leaves had been completely consumed while other parts had lost just the outer layers. I think of this last as the leaf eater’s version of a filet. The consumers of the greenery were not readily apparent.

There was plenty of frass evident on the leaf surface, so the little herbivore had to be nearby. Viewed from the side, the curled edge of the leaf appeared to have been manipulated to conceal a snug little hide away.

A webbed tunnel neatly held the leaf edge in a permanently curled position. Inside the tunnel was the larva responsible for the leaf damage. The larva is perfectly patterned to avoid detection. The green color is a good match for the green of the leaf and the black spots mimic the rows of frass.

Most leaves had at least one leaflet that harbored a larva. If these larvae get much larger, they could probably come close to defoliating the tree. A loss of leaves would not severely stress the tree this late in the season.

Blue Ash is my favorite ash, at least from an identification point of view. The young twigs are four angled and look square in cross-section. It’s always nice when a plant with many close relatives has a distinctive trait that splits it from the rest.

This Blue Ash was one of many growing in the woodland understory. It’s interesting that none of the others showed any signs of insect damage. Eggs are normally scattered between many individual plants which reduces the chances of the plant being damaged or the young being lost to a predator. Variations in behavior within a species are just as common as variations in color and patterning. These differences are a way of surviving changes that threaten the standard methods of behavior.


  1. Very cool photo of the caterpillar! Now that school has started again (I'm a teacher), you've got me thinking about "variations in behavior" as it applies in my classroom.

  2. Thanks, Anne. My wife is also a teacher and could add a lot to a discussion of classroom behavior.