Cottonwood leaf beetles.

A pair of cottonwood leaf beetles, on a cottonwood leaf.

Cottonwood is a kind of tree which is usually found around fresh water.  It grows fast and the trees themselves can become very large.  They only live a short time (for a tree) though, around 80 years, and leave their remains as fodder for all kinds of creatures.  The trees are important because of the stabilizing properties they have for banks and beaches.  While alive, the trees are a favourite food of beavers (the bark) and the leaves are consumed by numerous mammal and insect species.  One of those is the cottonwood beetle.

Cottonwood beetles reproduce rapidly and can spawn several generations in a season.  Although cottonwood is their primary food source, they will also take poplar, willow, and aspen.  In large numbers, these insects can defoliate a tree and are serious pests in management areas.  As summer ends adults will find their way under bark or leaf litter on the ground.  Those that survive predation and the scourage of winter emerge in the spring to lay eggs and begin the cycle again.

While shooting insects I am always on the lookout for evidence of their activity.  Signs include leaves with holes in them or parts missing and leaves which have been skeletonized.  Careful scrutiny of the nearby vegetation pays dividends occasionally.   I found a small number of cottonwood beetles by doing this very thing.  As I was walking along a beach I discovered a cottonwood tree with leaves sporting numerous holes.  A closer examination led to the discovery of these tiny herbivores. 

I photographed this with a 105 mm macro lens and an extension tube; I used a triple macro flash attachment for light.

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