Wicked Little Weevils

When it comes to species diversity, the insects reign over all other animals.  Roughly 900,000 species of insects are known, and the actual diversity is thought to be many times this number.  Another way to get the point across might be to say that insects account for more than 50% of all species described on Earth.

Yes, it's real. A metallic weevil.

Scanning electron microscope image of grain weevil.

Now, this includes all of those insects we see on a regular basis, from ants and bees to the flies.  The variation is so great that choosing a place to start is difficult.  A famous quote comes to mind.  When the famous geneticist J. B. S. Haldane was asked by some theologians what he could infer about God from his studies, he replied "God must have had an inordinate fondness for beetles.  He made so many of them."

A male giraffe weevil.

The elephant weevil.

The beetles do show amazing variety.  You are familiar with the ladybird beetle (a.k.a. ladybug), and you can likely picture others such as the scarabs.  Do weevils come to mind?  The weevil is a beetle that occurs worldwide and is represented by more than 60,000 species.  They tend to be small, often less than half of a centimeter in length, though some can grow to several centimeters.

Weevils are generally fairly easy to recognize; they possess a unique form.  Like the other insects, the weevils have compound eyes.  It is what emerges from between these eyes that enables them to be more quickly recognized. Weevils have an elongate snout, probably more properly referred to as a rostrum.  A pair of antennae also arise from the rostrum, but it is at the end of the rostrum that you find the mandibles and other mouthparts that perform the business of eating plant material.

Usually, this impacts us not at all, but various species of weevils do affect our crops.  There is a wheat weevil.  There is a flour weevil.  There is a maize weevil.  There is a cotton weevil.  Getting the picture?  I thought something like alfalfa might be weevil-free, but a quick search indeed revealed the alfalfa weevil.

What about fruits?  Aha!  As it turns out, various fruits are attacked by weevils as well, from the strawberry root weevil to the mango seed weevil.

A chestnut weevil.

What about dry fruits like nuts?  They were no exception.  Weevils affect everything from peanuts to chestnuts to hazelnuts.  As long as that last one does not interrupt my supply of Nutella, all will be okay.  Interestingly, these weevils drill into the protective shell of the nuts and lay eggs inside.  When the larvae hatch, they feast upon the nut inside until they are well developed enough to emerge.

One in particular, the boll weevil, wreaked havoc on cotton harvests in the United States.  If you are interested in that history, perhaps you should start with the Boll Weevil Monument in Alabama.

The red palm weevil.

Of course, there is much more to the weevil than its negative impact upon our crops.  They play an important role in terrestrial food webs, both in their action as herbivores and as food items themselves for species of other insects, birds and small mammals.

The Boll Weevil Monument, Alabama.