Webworms

July 31, 2021

As I left after fishing the reservoir earlier this week, I passed two trees that had infestations of webworms in their upper branches.  These moths lay their eggs on the tree leaves, and then wrap the nesting area in a silky web.  These must have been laid recently as the area of webbing was still relatively small.  As the eggs hatch and the 100’s of caterpillars (larvae) begin to grow, they encase ever larger areas of leaves beneath their web.  As the colony consumes the initial leaves in the vicinity of where the inch-wide white moth (adult) laid its eggs, the size of the webby mass increases.

The fall webworm (Hyphantria cunea) is a moth in the family Erebidae known principally for its larval stage, which creates the characteristic webbed nests on the tree limbs of a wide variety of hardwoods.  While it is considered a pest because of its unsightly web, it does not harm healthy trees.  When I looked online at the University of Arkansas Extension Service, I found the visible signs of infestation occur when the beige-brown webs begin to enclose the ends of the tree’s upper branches.  Fall webworms are a native moth that occurs throughout North America.  The web stage of the moth usually appears from June through August in Arkansas, but if a second generation is produced, can extend into October.  Fall webworm infestations tend to be episodic in nature with back-to-back bad webworm years occurring about once a decade, but some webworms are seen almost every season.

There are two different types of fall webworm found in Arkansas: the two-generation-a-year black-headed version and the single-generation-a-year orange-headed form.  Both occur across the South, but the orange-headed form is more common.  The moth usually lays her eggs around mid-June, and about 60-70 days are required to go from egg to pupal stage.  The black-headed form begins about four weeks earlier and can squeeze in a second generation.  I could not get close enough to determine which version was nesting high up in the trees.  I was just glad it was not my yard.

Thoughts:  I have been fascinated by the four-part life cycle of insects since I learned of it in elementary school.  What they did not teach is there are other types of insect metamorphosis.  The ametabolous (Greek for “having no metamorphosis”) insects look like tiny adults when they emerge from the egg.  Hemimetabolous (from “hemi” meaning part) insects have three distinct stages: egg, nymph, and adult.  Holometabolous (from “holo,” meaning “total”) insects have the four-part cycle (egg, larvae, pupae, adult).  Most of the world’s insect species are holometabolous, including butterflies, moths, true flies, ants, bees, and beetles.  I am constantly surprised by the difference between what I was taught in K-12 and the known reality found with further research.  I wonder if educators take the Jack Nicholson approach (“You can’t handle the truth!”), or if they do not know themselves.  For most of us, it seems we do not know.  We need to be willing to get the know “the rest of the story,” especially when it comes to issues of race and poverty.  Do the work.  Follow the science.  Change is coming and it starts with you.

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