Over the past several years, the number of individual toothache trees in the arboretum has steadily increased. The mature tree at the southwest corner of Mickle Hall continues to produce an abundance of fruit, and little volunteers continue to pop up each year. We have allowed the young trees to continue growing, even in locations that are unsuitable in the long-term. For instance, despite there being no future in the aboretum for a volunteer growing next to the trunk of a large mature tree, their leaves can provide food for a very interesting caterpillar.
Giant swallowtail (Papilio cresphontes) caterpillars have recently been spotted nibbling away on the leaves of a 4-year-old toothache tree (Zanthoxylum clava-herculis). Two caterpillars are captured in this photo. Do you see them?
Here we have another caterpillar, stuck to the spiny, slender trunk of the toothache tree.
They are funny looking creatures. You may even find their heterogenous and mottled appearance disgusting. They are camouflaged to resemble bird droppings! What wonderful diversity occurs in the natural world. And these critters are certainly thorough in their work of stripping the toothache tree of its foliage.
Rather than allowing the horde of caterpillars to defoliate a single tree, we remove a few individuals and place them on the volunteer toothache trees. As noted above, those trees that haven't been added to the catalogue because, based on their current location, they do not have a future in the arboretum.
We certainly want to make sure the caterpillars are well-fed--they turn into such lovely butterflies! Can you think of a better candidate for the "ugly duckling" of butterflies?
Since we have been studying the caterpillar of the giant swallowtail (Papilio cresphontes), we might as well look at another interesting caterpillar, this time an arboretum favorite. The Gulf fritillary has appeared on the arboretum blog more than once (here and here). Summertime brings an abundance of yellow passionflower (Passiflora lutea) to the arboretum and every summer the fritillary comes back to enjoy it.
Here we see the Gulf fritillary eating a leaf of the yellow passionflower. Currently, this is the only species of passionflower in the arboretum collection. We ought to make it a priority to plant purple passionflower (Passiflora incarnata) in the spring.
We briefly removed the caterpillar from its vine so that we could take a measurement. At the moment, it's less than an inch long.
It's small, but looks scary! Aren't those spikes marvelous? Never fear; it's all for show. Presumably this is to dissuade any would-be predators. This type of defense color pattern is a different tactic than the one exhibited by the caterpillar of the giant swallowtail.
By contrast, the caterpillar of the giant swallowtail is inconspicuous: it both blends in with its environment and looks like something you want to avoid eating or even touching: a waste product.
Autumnal weather has arrived in northwest Louisiana. This week we experienced low temperatures in the 30s, and over the next several days we expect high temperatures above 80℉. Although the mosquitoes are still buzzing about, the overall drop in temperature means that we can start moving plants around without fretting too much about survival rate. Today, a young, volunteer toothache tree (Zanthoxylum clava-herculis) was transplanted to a better location and officially added to the arboretum catalogue.
The volunteer toothache tree is pictured center. Some time within the past few years it germinated in the patch of dewberry (Rubus trivialis) on the west side of Mickle Hall, not far from the mature toothache tree. After the dewberry and yellow passion flower vines were pulled away from it, we could see the form of the young toothache tree: it is a little less than 2 feet tall, and it has a very long surface root.
This is a detail image of the toothache tree's long surface root. The little tree isn't connected to the soil at the base of its trunk, and it seems that the vines that had grown up around it were doing much of the work of holding it up straight.
Examining the volunteer toothache tree gave us another look at the giant swallowtail caterpillar (Papilio cresphontes). We talked about this species on our previous blog post.
In this video we can see the caterpillar eating part of a toothache leaf. (The video also shows how windy it was today!) When humans chew on the leaves of this tree, we experience a tingling sensation in the mouth, and if we chew on enough of the leaves, we experience a numbing effect.
This large, chunky caterpillar with a very interesting color scheme was relocated to the nearby mature toothache tree.
This toothache tree only has shallow roots, with one particularly long surface root. Not much digging was required to remove the tree from the dewberry patch.
The root system is surprisingly sparse, especially considering how healthy the trunk looks.
The toothache tree was transplanted from the top of a hill to the bottom of a hill in the hopes that it will have access to more water. It appears to be all by its lonesome on the Fitness Center lawn. A black oak (Quercus velutina) and black willow (Salix nigra) are growing nearby.
Two metal stakes flagged with pink tape serve as protection against lawn mower damage, and the pine straw mulch will help the soil retain moisture. This individual was thoroughly watered after planting was complete, and the soil moisture will need to be monitored until the tree enters dormancy.
Leaves at the very top already started to droop from the stress of relocation. They will hopefully perk back up soon. This same thing happened to the two other toothache trees that were transplanted this past spring. You can read about them here. Both of those young trees survived the summer.
At the southwest corner of Mickle Hall, our toothache tree (Zanthoxylum clava-herculis), is currently playing host to an interesting guest.
The guest has such intriguing camouflage. It's pictured center. Can you see it?
This is the caterpillar Papilio cresphontes. Does it resemble a tree lichen or something that a bird (or lizard) might have left behind? Either way, the bulbous shape and color combination allows this individual to blend in with its surroundings. It's a startlingly effective natural camouflage!
This individual measures 2 inches long. It vigorously scooted away as soon as I put it down. No threatening red 'tongue' was revealed during this encounter. After the brief photoshoot, the caterpillar was returned to the toothache tree to continue its snacking.
The caterpillar was originally found here, on this little toothache tree, which was planted in the arboretum this past spring. There were two caterpillars found on this small, young tree, and they were allowed to stay for several days since they didn't appear to have particularly large appetites and it's about time for our deciduous trees to drop their leaves. While on this little toothache, the caterpillars revealed their famous red 'tongues.'
After the two caterpillars nearly stripped all of the upper leaflets, it was time for them to be relocated. Both caterpillars were placed on the mature toothache tree at the southwest corner of Mickle Hall. Only one of which was later found for this photo blog. We hope the other one found a safe place for its next stage of development.
