Species Spotlight – Indian bean tree and the Catalpa sphynx moth

The catalpa, catawba, or Indian bean tree, is actually a couple of different species of showy flowering broadleaf trees – the Northern Catalpa (Catalpa speciosa) thrives in the Mississippi and Ohio River valleys from southern Tennessee to Indiana while the Southern Catalpa (Catalpa bignonioides) is native throughout southern Mississippi and Alabama into the edges of Georgia and Florida. The name speciosa refers to the extravagant clusters of orchid-like flowers.

These two trees are the sole source of food for the catalpa sphynx moth (Ceratomia catalpae), the caterpillars of which are commonly known around here as, “Catawba worms.” They make excellent fishing bait but when you grab the caterpillars they will puke up a noxious mixture of half-digested leaves that will stain your hands yellow.

My dad, in my youth, had an orchard of a dozen or so catalpa trees, from which he harvested the caterpillars. All that he did not use for fishing, he would freeze in Ziploc bags – and amazingly, when thawed next year or the year after the caterpillars would be just as feisty, just as nasty pukey, and just as good at catching fish.

When he planted the trees, he found a source for the caterpillars and transplanted bags of them to his trees, inoculating them so that he would have caterpillars in subsequent years. My dad would tie bamboo cane poles between the trees so that once the caterpillars had defoliated one tree they could easily get to the next tree and he would till the ground around each tree to break up the ground to make it easier for the larvae to get into the ground where they gestate into the Sphynx moths.

The caterpillars are voracious, and can completely defoliate the trees. Sometimes even multiple times in a year. Once a friend named Betty, upon seeing the ragged looking leaves on my dad’s trees, commented, “those poor trees!” We laughed about the “poor trees,” because not only do the caterpillars not hurt the trees, but they are symbiotic – the trees feed the insects and the insects fertilize the trees and cultivate the surface of the ground under them.

Now our trees are old, but they haven’t thrived in years. I don’t know if the trees have failed to thrive because of lack of the insects, but we have not had caterpillars for years either. We suspect that the city mosquito control spray has killed the moths. Of all of our trees, the ones nearest the road eventually withered and died, while only the 2-3 farthest from the road (and the mosquito sprayers) have flourished and reached mature height.

Recently I was reading on the internet that Catalpa trees can be propagated easily from impossibly large clippings. This source says to take a 3-4 foot long clipping, strip all the leaves (as if a caterpillar had eaten it), plant it a foot deep in the ground, and water it daily until it has new leaves. It is said that this sort of propagation is 80% successful. Sounds like I have another science experiment on my hands!

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