Two caterpillars that I hadn’t seen before were introduced to me this past week. Both have odd names. One is named turbulent phosphila or two headed caterpillar (Phosphila turbulenta), the other is called monkey slug or hag moth caterpillar (phobetron epithelium).
One day last week, Facilities Tech, Wayne was working in the brush below the boardwalk here at the Museum. I happened to be standing there when he emerged from the woods beneath the wooden walkway after completing his duties. He had a hitchhiker on his shoulder. Wayne must have brushed up against a greenbrier vine.
The hitchhiker was a little over an inch in length. It was a caterpillar which is exclusive to greenbrier, a turbulent phosphila. Of course, I didn’t know what it was until I took a photo of the caterpillar and compared it to other photographs both on the internet and in reference books in my office. The pattern on the caterpillar was distinctive, and it had markings on both its head and the tip of its abdomen which made me pause and wonder, which end is the head? A close look revealed three pair of true legs which in all caterpillars are located on the thorax just behind the head.
The caterpillar had fine, black and white or yellow stripes down the length of its body. The underside was orange. Each end of the body was black with white spots and the tip of the abdomen was swollen. It’s been suggested that the swollen abdomen in combination with the white spots are meant to fool predators into thinking the abdomen is the head end of the caterpillar. I’m not convinced.
That type of fakery may work with butterflies, where false eyespots and elongated scaling on hindwings (false antennae) make a predator think they’re attacking the head of a butterfly, when instead they come away with a beak full of wing. The butterfly then flies off to safety, albeit with a bit less wing than it had before. That sort of strategic camouflage won’t work with caterpillars.
It doesn’t matter which end of a caterpillar a bird latches onto, it’s curtains for the little larva. If the caterpillar’s too large for the bird to swallow whole, it will thrash it about against a tree branch before picking it apart.
The bright coloration of the phosphila probably serves to convince any would be predators that the caterpillar is toxic. Many brightly colored insects are toxic. They get their toxicity from the plants they eat. Greenbrier, though, which is what turbulent phosphila caterpillars eat, is not toxic. The bright colors may be an evolutionary ruse to keep predators at bay.
Where does this moth larva get its name? I’m not quite sure. However, since there appears to be two heads on the caterpillar, perhaps the name turbulent indicates confusion, as in, which end is up. Names of flora and fauna often derive from greek mythology or have greek roots. Turbulent phosphila could possibly mean confused light-loving moth, phos = light, phila = love or friendship. All moths, as adults, seem to be attracted to lights, perhaps this one especially so. Or, maybe the moth avoids lights (confused).
The hag moth caterpillar will be featured in a future post.