Small Reddish-Brown Caterpillar – Immature Pinion?

2014 June 11

On July 7, 2013, I had just come back from walking the dog along the trail through the woods, and Sandy noticed this little reddish-brown caterpillar on my shoulder.

It was fairly small, less than an inch long, and had that kind of indefinable air of immaturity, so I think it was only a half-grown caterpillar. Which makes identification even more difficult than for an older caterpillar, because a lot of caterpillars have never had their younger instars documented properly.

From the pattern of spots and stripes, though, it looks familiar. Specifically, aside from the color it looks a lot like this one, which I had decided at the time was most likely one of the Pinions in the genus Lithophane[1].

BugGuide says that there are 52 known species of Pinions in North America, with three of them having been just discovered in 2006. And most of these are generally found along the US/Canada border, so there are a lot of possibilities here. And, as Wagner says in “Owlet Caterpillars of Eastern North America” in the entry for the “Nameless Pinion”[2],

Until a reliable key to Lithophane larvae is authored, it is best to base identifications on the adults, which can be difficult enough

Like a lot of caterpillars, these are practically blind. The big bulges on the sides of the head are not eyes, they are just the location of the massive chewing muscles that an eating machine like a caterpillar needs to plow through all those leaves.

The eyes, such as they are, are just little eyespots that are mainly just sensitive to light and dark, with pretty much no imaging capability.

Pinion caterpillars are evidently a bit notorious for going cannibalistic, so if one tries to rear them to adulthood, it is best to keep them separated.

In this area, we can expect the adults to emerge in the fall, fly for a brief period, and then find a place to hibernate. They then come out in the early spring to lay eggs. This would allow them to get their eggs laid sooner than the moths that overwinter as pupae (and therefore have to take time to finish maturing before they emerge). So, we should expect to see pinion caterpillars in the really early caterpillar populations. Carole informed me in a comment to the previous Pinion post that the caterpillars need to feed on young, freshly-budded leaves, and will gradually starve if fed older leaves, which would go along with the eggs being laid early in the season. They would be hatching out and starting to feed right as the leaves are coming out of the buds, and are at their most tender and delicious stage.

[1] It also looks quite a lot like this (somewhat greener) one, which I had previously posted as part of a collection of “unidentified green caterpillars”.

The thing is, that one was found in Sandy’s hair after a walk in the woods, about the same time of year. Whatever they are, they seem to like to drop on people.

[2] So, does “Nameless Pinion” mean that it has no name? Or is “nameless” actually its name, in which case it is not nameless at all? If this were a Star Trek episode, this is the sort of question that you could use to crash dictatorial computers and rogue androids.

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