Worms in Canada

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A reader wrote to us about an interesting cycle of insects and worms that he has observed at his house in Canada (London, Ontario, more precisely). Over the summer, there were lots of fairly large insects in his house – they were about one to two inches (about 2.5 to 5 centimeters) long from wing tip to wing tip. The following spring, the reader found tons of worms on his driveway. The worms were black and brown (or a blackish, brownish mix, technically) and they wouldn’t go away, even after our reader tried to blow them away with a leaf blower. The worms, which are about an inch to an inch and a half in length, come out in great numbers after it rains. What are the worms that our reader is finding? Are the worms specific to Canada? Is there any connection between the summer insects and the spring worms?

These are the types of questions we might have expected our reader to ask, but he actually didn’t ask anything at all. However, he did end his email with one word, “help,” followed by nothing but a period, which we found almost poetic in its simplicity, so clearly he wants some information from us.

There is a lot of helpful information in our reader’s email – we know where our reader lives, for example, and we also know the size and color of the worms he is finding – but we are still left with a number of questions (and a strong desire for a picture). Most pressingly, we can’t see any connection between the insects in the reader’s house and the worms that appeared several months later. Of course, this concern is tied to other bits of missing information, such as the type of insect our reader is finding in his house. It has a reasonably large wingspan, but that doesn’t narrow our options very much. Is our reader perhaps dealing with a type of butterfly or moth, which often do have wingspans in the range described by our reader? If so, the “worms” our reader found could potentially be the larval form of butterflies and moths (which are more commonly known as caterpillars), but in truth this doesn’t make much sense. For one, the reader likely would have said he found butterflies or moths (the vagueness of the word “insect” seems to imply something less well-known), and more to the point, we don’t understand how the time line would work out in this scenario. Occasionally caterpillars born late in the year will stay in the pupal stage of development all winter, but then in the spring they will emerge as adult moths and butterflies, not as caterpillars that could be mistaken as worms.

Because of all the blanks we need filled in, it is impossible for us to engage in anything but pure speculation. With that in mind, our best guess is that the insects in the house are not actually connected to the worms. We say this largely because the worms described by our reader sound a lot like regular earthworms, which are notorious for invading peoples’ driveways after it rains. Earthworms often take advantage of temporarily wet conditions to move to new places, as it is normally too dry for earthworms to come out of the moist soil (their skin needs to be wet in order for them to breathe). The reader’s physical description of the worms he is finding fairly well matches up with this possibility, although it is a bit strange that all of the worms are only an inch or an inch and a half long. Earthworms can of course be this size, but they can also get quite a bit bigger than this. Maybe most of the worms are still relatively immature and therefore still growing? Of course, we have no idea.

Unfortunately, we can’t really say anything else. We can’t check our guess against any pictures, and we simply aren’t working with very much information. We realize that this doesn’t provide much help for our reader, which is the only thing he wanted, but perhaps we have started him in the right direction. If the worms are totally unrelated to the insects, than perhaps he can at least begin to address each issue separately. As always, we wish our reader the best of luck with his problem.


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