Caterpillar Found in Moon Cake Tin

2013 November 23

Sandy has developed a fondness for Moon Cakes, a traditional Chinese food that is normally eaten at the Mid-Autumn Festival. Our local Asian grocery store sells them individually wrapped, and sealed into colorful steel tins, and has them in stock usually until around the Chinese New Year. So, anyway, Sandy bought a tin of them on February 1, 2013. And, when she opened up the box, she found this little caterpillar inside – a little guy, only about a third of an inch long.

There was only the one, and it was outside the individual plastic wraps on the moon cakes. It was just inside the tin, so the actual cakes were not infested[1]. Since the tin seals pretty tightly, it must have gotten into there just as the cakes were being packed into the tin in China.

So, this is clearly one of the several kinds of “meal” or “pantry” moths. These are moths that eat grains and flours, and that have very little need for water (they are probably descended from something that originally lived in a desert).

Once they get established, the various kinds of pantry moths are hard to eradicate. They are so tiny that it only takes a little bit of ignored flour or grain dust in the corner to get a population going, and then the adult moths can spread quickly to any exposed grains in a pantry, grocery store, feed mill, or food preparation facility.

Since there are several different kinds, we decided to try raising this one up to see what the adult looked like. So I put it in a little bottle with a slightly moistened piece of graham cracker, and waited. After a bit, it made a thin cocoon and pupa – here’s the pupal skin.

And here’s the moth. I was actually expecting an Indian Meal Moth, which are pretty common worldwide, but the wing patterning is all wrong for that.

From the silvery wings, it looks more like a Mediterranean Flour Moth, Ephestia kuehniella, although that doesn’t look quite right either. It could just as easily be some exotic[2] Chinese flour pest moth.

The face looks pretty disreputable, with disorganized hair all over it. It almost looks like it even has rough, matted hair all over its eyes.

So, anyway, whatever exact species this is, it is clearly a pest moth, and might even be a new species for our area. So I didn’t release it. The last thing we need is moths getting into our pantry again[3]

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[1] If you’ve ever read any of the “Horatio Hornblower” stories, these caterpillars would have been likely to infest the ship’s biscuits along with the “weevils” that he was always knocking out of the biscuits by rapping them on the table. They are the sort of thing that would get counted in with the “weevils”, because they look pretty similar. And if you are trying to knock them out of your biscuit, one probably isn’t going to spend a lot of time trying to ID the exact species anyway.

[2] Just because they are exotic, doesn’t mean they look like much.

[3] We had a bad infestation of Indian Meal Moths some years ago, from a bag of cheap birdseed that had a lot of them in it. They got into things like boxes of cornmeal and bags of flour, leaving masses of webbing all over the stored foods. It took some time to get everything they might go after sealed into boxes, freeze or dispose of the items they had gotten into, and generally make it impossible for them to raise more caterpillars. These days, we either don’t bring birdseed into the house at all, or we freeze it first to kill off any moth caterpillars that might be inside.

2 Responses leave one →
  1. November 23, 2013

    The bottom two photos make it look like it was made of burlap.

  2. Bridget permalink
    November 25, 2013

    When I had a pet hamster, we had these (or something like these) infest it’s hamster biscuit things. Needless to say, we started storing the food in airtight jars after that. It freaked me out at the time, but I was maybe 10. Now I’d be kind of fascinated by them.

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