Wednesday, September 16, 2015

What's Eating the Redbuds?

When people ask me what ornamental tree I would recommend for home landscaping, Redbud is generally my instant response.  My reason for this response typically causes my inquisitors to lose interest in my opinions.  They are expecting me to make some point about the beauty of the tree or the rapid rate at which it grows or the fact that it doesn’t get large enough to fall over and smash your house, but I like Redbud because it is a preferred food of so many animals.  From the time the first flower bud begins to open in the spring until the last leaf drops in the fall, something is consuming the Redbud.  About 20 years ago, I planted two Redbuds at the corner of my garage, so I could more easily follow the season long parade of Redbud predators.  These trees have since grown tall and lost most of their lower branches.  From below, I can see the chewed leaves and know that something interesting is living above.

Fortunately, the trees I planted have spread many seeds.  I’ve let some of the resulting seedlings grow along the side of the garage, so I can have a few Redbud branches at my eye level.  Many different types of animals feed on the tree through the year, but in September it’s the caterpillars that dominate.  I took a few minutes to photograph some of the current residents.

First off, I should probably mention the species that actually targets the Redbud over other plant species.  The Redbud Leaf Roller can likely be found on any Redbud Tree.  Because of its habit of folding over a leaf edge and webbing it in place to form a sanctuary in which to feed, the Redbud Leaf Roller is not seen by many people.

You have to unfold the leaf to reveal the creator.  These caterpillars are known as skeletonizers because of their habit of leaving the leaf veins and a thin layer of tissue behind as they feed.  Inside the fold of the leaf, the caterpillar eats and leaves its droppings.  A nice little package that hides most evidence of the caterpillar.

Hanging by lengths of silk, these small green caterpillars disperse themselves around the tree.  It doesn’t make sense to me that they are all just accidently falling off of their leaves.   It seems like poor survival skills to be unable to keep hold of your food supply.  Some of the caterpillars keep lowering themselves until they arrive at another leaf.  Others sway in the breeze and grab onto leaves or branches.  Still others climb back up their thread, apparently arriving at the end of their tethers with nowhere to go.  I think much of their activity is in an effort to scatter themselves around the area.

I believe these thread travelers are early instars of the Redbud Leaf Roller.  I’ve found many living in refuges made by webbing together the edges of two neighboring leaves.  Perhaps the younger caterpillars do not have the strength to fold a leaf edge over on itself and take advantage of an already occurring situation.

Colorful caterpillars are always more colorful when they come in a group.  These are early instars of the Red-humped caterpillar.  Like most of the caterpillar species found on the Redbud, these caterpillars feed on a variety of woody plant species.  A few end up on the Redbuds each year.

The final instar of the Red-humped caterpillar.  Having groups of different ages suggests that more than one female planted her eggs on this tree.

Fall Webworms are also generalist feeders, but they never miss laying eggs on the Redbud. 

A mass of webbing is generally the first indication of Fall Webworms.  The group stays together until its final instar.

The last stage caterpillars head off on their own, sometimes staying on the original host tree and other times wandering to a new location.

The caterpillar of the American Dagger Moth.  I personally think of this as the English Sheepdog caterpillar, because of the mass of hairs hanging down over the face.

Here’s a caterpillar that’s often overlooked as a bit of fluff.  This is the early instar of the Black-waved Flannel Caterpillar.

Final instar of the Black-waved Flannel Caterpillar looks quite different from its earlier edition.


Skiff Moth caterpillars don’t look at all like living animals.  They look more to me like galls or other plant deformities.

Their coloration can vary.  This one carries an image on its back that looks more like a birds face than do many actual bird’s faces.  This should certainly startle any predators approaching from the rear.

The Yellow-shouldered slug.  This is one of many caterpillars collectively called slug caterpillars.  It’s easy to see why they were given that designation.  Most in the group are slow moving and look like an oblong blob.

You may not guess it from the name, but many of the slug caterpillars are the showiest caterpillars around.  This is the Saddleback Caterpillar.  Those spines are far from being just ornamental.  I’ve received five stings from this species this year: Two shoulder, One arm, One neck, One ear.  It takes my body about 30 minutes to deal with the toxin and get back to normal.  This caterpillar routinely sits near the edge of the lower side of the leaf with the tips of the spines sticking out.  That makes it very easy to accidently brush against the spines.

The Spiny-oak Slug is another stinger, but it generally doesn’t spend so much time at the edge of the leaf.  This is a variable species that can display a wide range of color patterns.

A real winner in the color category is the Stinging Rose Caterpillar.  The warning here is included in the name.  It may have the appearance of a fancy piece of hard candy, but this is one morsel you don’t want to touch.

The black and white pattern of the Hickory Tussock Moth caterpillar reminds me of white Bengal Tigers.  This specimen seems to be shedding.

I found many of this species on the Redbud, but wasn’t finding much evidence that they were feeding.  There was a chance that they were just migrating over from some nearby Black Walnuts, a favorite food plant.  Then I found this guy carving a large hole in the middle of a Redbud leaf and decided that they must also eat Redbud.

There are also several caterpillars that I can’t put a name to.  This little guy had three parasitoid larvae riding its back.  I found this curious because the caterpillar was trudging along as though nothing was wrong.  Typically, the parasitoid larvae would feed and grow inside the caterpillar and then emerge to spin cocoons and pupate on the caterpillar’s skin.  As large as these larvae are, it seems there would have been little left if they had been feeding inside that small caterpillar.  The caterpillar should have at least moved sluggishly or remained stationary as I’ve seen so many other caterpillars do in similar situations.

Finally, this European Hornet, which is not a caterpillar of any kind, searched leaf after leaf and appeared to be following me as I examined the Redbud.  I thought it might be hunting caterpillars, or some other creature on the tree, but it never seemed to find anything.  I’ll just add its behavior to my enormous list of things I would one day like to understand.

8 comments:

  1. Those spony slugs are amazing! We can keep Redbuds alive here, but they never get warm enough to bloom.

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    1. Hi, Stew. It's a shame Redbuds won't bloom in your area. They put on a spectacular spring display down here.

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  2. Hi Steve,

    Great post! I especially like the Euplectrus external wasp larvae. I've found their cocoons under the caterpillar corpse but have not seen the larvae. http://bugguide.net/node/view/104690/bgimage

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    1. Thanks, Laura. Also, thanks for the BugGuide link. I wasn't familiar with ectoparasitoids. Since the wasp larvae had never been inside the caterpillar, I understand why the caterpillar could still have so much life left to it.

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  3. ...wow! Loved this post, Steve. I learned a lot. I have about 5 redbuds in my yard (and more keep growing). I've seen a few of the species you highlight, but I've never see a Black-waved Flannel Caterpillar or any of the slugs. I'll watch out for the Saddleback Caterpillar! I need to go and take a close look!

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    1. Thanks, Kelly. I hope you are lucky enough to find some of the slugs. They're fascinating to watch.

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  4. Such gorgeous caterpillars! The slugs are tons of fun (except when they sting you). I'll definitely add Redbuds to my list of wildlife trees for a future yard. Thanks for the post.

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    1. Hi, Jodi. You won't be disappointed with Redbuds in the landscape. I'm always finding something new living on my Redbuds.

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