Posted by: Ross Gardner | September 19, 2012

What a load of galls!

By the time the summer nears its end the foliage on trees and shrubs everywhere is looking rather tired.  They have endured another year of weather – good and bad, expended their lustre on the everyday efforts of growth and change, and of course, withstood the ravages of those small lives in their millions than seek to live their own life cycles within and around leaf and branch.

One group of creatures has in particular been catching my eye just lately, yet I haven’t knowingly laid eyes on one, not least because they may only measure a mere 2 or 3mm in length.  A gall wasp is indeed a tiny insect, but the signs of their presence are a great deal easier to observe.  The gall produced by the wasp is a result of an egg laid into the host plant, which causes the tissue of the plant to swell around it.  The resultant grub hatches into a ready supply of food and a safe place to live and pupate.

Knopper Gall (Andricus quercuscalicis). Copyright 2012 Ross Gardner.

There are a great many species of gall wasp and a wide range of host plants; the oak is among those that are parasitized by numerous different species.  It is among such trees that the doings of these tiny insects has been drawing my attention and catching stirring my imagination.  The galls of different species may come in a variety of shape and size, so as to belie the similarity of the adults that create them.  The contorted knobs of the Knopper Gall (Andricus quercuscalicis) disfiguring the acorns; the little discs of Spangle Galls (Neuroterus quercusbaccarum) and Silk Button Galls (Neuroterus numismalis) by the dozen on the underside of the leaves; the small, smooth spheres of Cherry Galls (Cynips sp.), also attach to the leaf’s underneath.  There are others besides.

With the autumn’s ascendency growing around the countryside and the time of summer exuberance beginning to draw to a close, it is these curious little growths that adorn their giant hosts that remind me still of the vastness of nature that resides beyond our normal observation and in such quantities as would boggle the mind.

Common Spangle Galls (Neuroterus quercusbaccarum) – a single Silk Button Gall (N. numismalis) can be seen at the top of the leaf. Copyright 2012 Ross Gardner.

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