2012 August 25

When Sandy goes out ice-fishing, she likes to use “waxworms”, which all of the local bait shops carry. They are these creamy-white caterpillars, about 2 cm long. Here’s one in Sam’s hand, that was left over from a fishing trip on January 15, 2012:

Their prolegs are not very well developed, so they look more grublike than is typical for caterpillars.

Since they are sold near maturity, they will pupate within a week or so after purchase if you keep them at room temperature (but can stay as live caterpillars for weeks if they are refrigerated). These were left out to see what they would turn into, so we ended up with a number of pupae (which are pretty typical moth pupae):

They then emerge as kind of nondescript-looking moths about two weeks later (this one emerged on February 5). The background object is a quarter, so you can see that they aren’t particularly large moths.

When I first saw these years ago, I thought that they were called waxworms because they had kind of a waxy appearance. But then I found out that they are actually caterpillars of the Greater Wax Moth, Galleria mellonella. Which get their name because the caterpillars infest beehives and destroy the wax combs. They chew through the wax and eat the pupal skins and cocoons from the bee larvae, and in the process they make a huge mess. They aren’t native to North America, but they have been unintentionally introduced everywhere that honeybees are introduced. Luckily, they aren’t very cold-tolerant, and so in our local climate they don’t do well in the wild because it is a long way between beehives and they have a hard time finding shelter for the winter. I still don’t want to let them get established in our hives, though.

The very feature that makes them pests (they grow readily in an enclosed box provided there is food available) also makes them very convenient to raise domestically, which is why they have become popular for fishing bait and feeding to insectivorous pets. They also have less chitinous skins than, say, mealworms, so they are more digestible.

9 Responses
  1. August 25, 2012

    I’m surprised that they are still sold as bait even though they don’t survive winter. Insects have been known to adapt and we certainly don’t need another introduced pest.

  2. August 26, 2012

    I think that, in this particular case, it is already far too late to worry about introducing them in new areas. They were carried here pretty much as soon as honeybees were introduced, and according to all my beekeeping books they live pretty much everywhere that honeybees exist. It’s just that they normally are only present at a low level with the bees keeping their numbers down, so one doesn’t notice them unless the hive gets too weak to patrol all of their comb space during the warmer part of the year. At which point, the wax moth population explodes. I’m sure they are already around here, and if I ever get too careless with storing frames of drawn comb I’m probably going to find that out the hard way.

    Of course, in general bait really is a significant route for introducing invasive species. The problem is that, as far as I can see, bait is practically unregulated. If there are any laws in place to control what gets used for bait, or where it is taken to, they sure aren’t very well enforced. There isn’t even a lot of awareness of what is, or is not, invasive bait. For example, it wasn’t until just a few years ago that I found out that *earthworms* are invasive in the Upper Midwest and Canada!

    At least wax moths aren’t aquatic animals, so they aren’t going to be carried from lake to lake this way. Not like minnows or crayfish.

  3. August 26, 2012

    Curious about Alberta’s regulations, I looked it up. http://www.albertaregulations.ca/fishingregs/general-regs.html#fishingwithbait
    I see that wax worms are used here too.

  4. August 28, 2012

    Wondering how bees, equipped with stingers they use so liberally when 5-year-olds with jars try to capture them off rose bushes*, I stopped by the “waxworms make a mess” link and discovered that the bees can indeed keep them in check, if they can find the little grubs. That made me feel a little better. I stopped wondering if bees just wanted to persecute little kids.

    * – Not me, mind you. It was another kid I read about somewhere. I’d never have tried to capture bees in a jar. No, I was using that jar to store pennies and nickels for a rainy day. I have no idea why the holes were poked in the lid. Someone must have done that while I wasn’t looking.

  5. August 28, 2012

    Ah, yes, “some other kid”. I see 🙂

    Along those lines, we just did another presentation on insects at the library last week, and one of the things we took was an active wasp nest in a mason jar. What you do, see, is get a wide-mouthed mason jar (with a lid) and a thin scraping tool of some sort (I used one of the little pry-bars used for opening up beehives, but a putty knife would work just as well). Then you find an exposed and accessible nest that is smaller than the mouth of the jar. You creep up to it, and then briskly (but carefully!) slip the jar over the nest and seat it tight against whatever the nest is hanging from. Then you slide the scraping tool between the jar lid and the surface, and cut off the little neck on the nest so that it falls into the jar. Then you drop the tool, get the lid out of your pocket (you *did* remember to put it in your pocket, right?), and then quickly lower the jar and slap on the lid before too many wasps escape. And voila! A wasp nest in a jar! And I only got stung once!

  6. August 29, 2012

    I’m sure you’ll be hearing from the wasps’ lawyer.

  7. December 20, 2015

    So If You Find Them In The Wing, Do You Kill It Or Not?
    Cause Mine Is In The Process Of Cocooning O.O

  8. December 22, 2015


    That depends. Do you keep bees? In that case, you probably shouldn’t let them grow up to adults. Otherwise, don’t worry about it.

  9. Missy permalink
    November 2, 2019

    I found a caterpillar that looks like this in my backyard on the ground. It’s cold here so it was all curled up. Glad to know it’s not a hairless version of the poisonous white caterpillar. Thanks for the info

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