Nature will not be admired by proxy.
Seems as though my schedule (and the heat) have kept me from some of my usual yard patrols, so I finally went out the other day for a walk-about to see what I could see. It started with my eye catching something out of place on a hickory sapling near the gate…a bright green spot at the edge of a leaf…
When I walked over, I could see by the distinctive triangle-shaped head, framed by a pair of yellow stripes, that it was an old acquaintance – the larva of a walnut sphinx moth, Amorpha juglandis.
I did a short blog post on this cool species a couple of years ago when I found out it has an unusual ability…it is one of the few caterpillars that can make sounds! Researchers discovered it can make a high-pitched whistle by quickly expelling air out of its eighth pair of spiracles (the small breathing tube holes along the sides of caterpillars). Studies have shown that the sound may be enough to scare off potential bird predators.
Even though I probably disturbed this little guy while taking its picture (they usually feed on the underside of leaves so I had to flip him over for a full profile pic), I heard no whistle. I can’t decide whether their sound is outside my range of hearing (like many warblers) or these caterpillars just realize I am a long-time fan of their kind and present no threat. After photographing this species, I decided to walk around for a few minutes to see what else I might find.
Just a few feet away on another hickory sapling, I found an aggregation of strange, hairy larvae that turned out to be walnut caterpillars, Datana integerrima. What made me notice was a couple of leaves that had been heavily chewed. As I got closer, I could see something that looked like my barber had glued some of my trimmings all over a couple of black worms. When I touched the leaf, they quickly arched into a c-shape, a classic defense pose for members of this genus of caterpillars.
I flipped the leaf to get a better look and found that they had all just molted. This is typical for this species, which is known to move down out of the trees where they are feeding in masses in order to molt. Walnut caterpillars generally have at least two generations per year in the south and can periodically be serious defoliators of localized populations of black walnut, pecans, and various species of hickory. I have never seen them cause significant problems in this area as they seem to be controlled fairly well by natural predators and parasites.
So, in just a few minutes time just outside my door, within a span of less than thirty feet, I was rewarded with glimpses of two fascinating species that share my habitat. It is always good to be reminded that to really enjoy nature, you have to be out in it.
Usually I’m just annoyed at caterpillars because they’re devouring something I’ve planted for myself – not them! – but your perspective has helped remind me that we’re all in this together. As always, great pics!
Thanks, Daniel. Yes, a good lesson for us all.
When we were recently at Moth Night at Eno River State Park I kept hearing a high pitched sound and thought one of the kids attending had a whistle. Now I am certain it was the Walnut Sphinx caterpillar! I never even considered that caterpillars could make sounds!