The Worms Crawl In but Do They Swim?

This is an update of a tale was originally published by Loret T. Setters on August 22, 2014 at the defunct national blog nativeplantwildlifegarden[dot]com beautifulwildlifegarden[dot]com.

baldcypressmay2013This week I noticed that there was some webbing on a Baldcypress tree I planted a while back. At some point my property was likely home to many of these trees as is evident by decaying knees I see when the pond level gets low.  These majestic trees require wet conditions during part of the year so are often seen reflecting in the waters of swamps, ponds and rivers.  I’ve added a couple as a part of restoration efforts to return appropriate native plants to my property’s ecosystem.

Why are some caterpillars called worms?
Why are some caterpillars called worms?

I did a little research and found that these trees can be host to the Fall Webworm (Hyphantria cunea) which is a generalist that can use any of a multitude of trees as a food source.  Bugguide notes there are possibly 120 hardwood species as potential hosts.  The topmost photo shows a grouping on Elderberry.  Webworms aren’t worms at all, but moth caterpillars. The adults are pretty little things…white or white with black dots, rather like a Dalmatian of the Lepidoptera set.

My goodness something poops a lot
My goodness something poops a lot

I noticed a single web and initially didn’t see any caterpillars, just a ton of messy frass (caterpillar poop). It started on the tip of just one small branch, but over a period of a week, it had spread to several branches. With my Baldcypress being so young, I was a little concerned that it might be losing too much foliage to survive.  My tree is a mere 6-foot or so and has really just started upward growth in the past year with initial years dedicated to working on underground root systems.

As far as Fall Webworms, according to Florida County Extension Services (pdf):

“The damage caused by this species is considered aesthetic. Typically it is late in the season when the webbing is noticed and the bald cypress would be defoliating soon anyway, so spraying won’t protect the trees. Also, with bald cypress which typically grows along ponds and waterways, the drift from spraying with some insecticides could endanger aquatic life, that means dead fish and frogs, etc. So, it is better to let nature take its course and do nothing.”

When I finally spotted the actual caterpillars, there were so many that my concern got the best of me.  Rather than let nature take its course, I decided to handpick off a bunch of the caterpillars. Despite being a bugaholic, I don’t like touching the critters without something between them and my skin, so I covered my hand with a plastic bag.

My my there are a lot of these guys
My my there are a lot of these guys

Now, what to do with my handful of critters…I really didn’t want to just squish them, figuring something somewhere may want a fresh LIVE meal.  AHHHHH!!!!  FISH!  maybe the fish would like a free meal.

I headed over to the pond and dropped a few into the water.  There was immediate activity as the mosquito fish converged on the wigglers.  Unfortunately the arrivals were mostly fry and the caterpillars were 4-5 times their size so the fish quickly headed off to find something to eat that was not quite so beefy.

Finally! A fish large enough to eat one of these buggers
Finally! A fish large enough to eat one of these buggers

I was a little disappointed when suddenly, one of the largest mosquito fish came over and snapped up a caterpillar whole. Just the end of the cat was hanging from its mouth as it chomped away.

It was slow going, with many of the fish sniffing, but less than interested.  I thought perhaps I would see the larger Blue Gill fish and Largemouth Bass, but they were nowhere to be found.  Still, an occasional larger mosquito fish was partaking in the bounty, so I headed back to the tree to gather some more tidbits.

Webworms are pretty smart creatures.  They spin a web around the entire gang and peacefully dine within the nice comfy confines.  Predators are reluctant to get caught in the webs, so the caterpillars are free to munch away without being disturbed.  That is until the BRAVE human comes along with protection from sticky webs in the form of the Wal-Mart bag on her hand.

Well, well, well, someone saw an opening and took advantage
Well, well, well, someone saw an opening and took advantage

When I got back to the tree, I saw a Southern Yellowjacket wasp (Vespula squamosa) had taken advantage of a break in the web to grab a caterpillar. He seemed to be munching on the caterpillar and I learned that they feed their larva masticated (chewed) arthropods.

It seems that

“wasps perform a valuable service in destroying many insects that attack cultivated and ornamental plants”.

Yellowjackets are pretty aggressive often proving dangerous with their vast numbers at nests and ability to sting multiple times, so they are not my favorite creatures. But, they appear to be a step up the food chain from the Webworms, so I have a newfound respect for them.  Still, if Yellowjackets nest close to the house they will be toast. Stings can be dangerous as they don’t let up when defending their nest.  My little guy seemed less than interested in me as she played with her food, but then again she was only preparing the meal for the young, not putting the dinner plate out at the living quarters.

(Hyphantria cunea)
(Hyphantria cunea)

Other natural enemies used in biological control of Hyphantria cunea are certain chalcid wasps that are parasitoids in the Pteromalidae family. It says that these attack pupae so in my case, they would be too late to save the foliage, although it would impact next years’ population of the moths who do the egg laying.

Still, not wanting to see my tree leafless this early in the season, I stripped another grouping of the Webworms and tossed them into the pond.  This group was still attached to some greenery contained in some webbing so it looked like a little raft of refugees floating and desperately trying to return to land as they wriggled in unison.  And the “sharks” were circling.

A “raft” of webworms float on the waters
A “raft” of webworms float on the waters

So, while Webworms may not be a favorite, they do feed other wildlife and heck, all that frass must be full of great fertilizing nutrients which will return to the soil to help my Baldcycpress grow to be a majestic tree like others in the neighborhood. That will give the Webworms more meals and they’ll be grateful that I won’t be able to reach up and grab them any longer.

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