Tiny Newly-Hatched Caterpillar

2021 September 12

On August 13, 2021, Sam came up to me with something extremely tiny on her arm, so small that it wasn’t quite possible to make out what it was with the naked eye. So, I ran my camera lens up to 3X magnification[1], and got some pictures.


And now we can see it is an extremely tiny caterpillar. It probably just hatched from its egg. Incidentally, those are Sam’s arm hairs it is crawling on. Her arm hair is so fine that it is difficult to see with the naked eye, to give some idea of the scale of this caterpillar.


Looking closer, we can see that it has some hairs, but it is pretty sparse, so we don’t know if it will grow up to be a hairy caterpillar or a smooth one. It also has an enormous head relative to its body. This makes it clear what a caterpillar is: it is a mouth attached to a food-storage tube. And this one hasn’t had a chance to stuff its tube.


Since we didn’t have any idea where it came from, or what it was going to want to eat, and caterpillars this small have a pretty high mortality rate, it wasn’t really practical to try raising it up. So, we let it go. About all we know is that it is the caterpillar of a species that lays eggs in mid-summer. It actually looks quite a lot like the hatchling caterpillars of the Pearly Underwing, which we have found laying eggs on our house in the past. I don’t have any way of knowing if it is that exact species, but the Pearly Underwings are a variety of cutworm moth, and so this is pretty likely to be a caterpillar of one of the cutworms. Cutworms usually overwinter as partially-grown caterpillars buried in the ground, so the timing is right to be one of them, too.

[1] In macrophotography, magnification is relative to the size of the image sensor. So a macro lens at 1X magnification, puts an image on the camera’s sensor that is the same size as the actual object. The thing is, though, the sensor is actually pretty small. The one in my Canon 40D is only 22.2 x 14.8 mm, giving a diagonal measurement of just about an inch. But when we view an actual picture, the image is blown up much larger, at least 5-10 times bigger than the image sensor. So when we look at a picture taken at “1X Macro”, the actual picture is more like 10 times the actual size. This means that when I crank up my lens to “3X”, we end up seeing the insect at more like 30 times magnification.

One Response
  1. September 21, 2021

    Awwww. I’m such a sucker for babies that all I want to do is feed it.

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