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The Straight Dope


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I think I found something in your book More of the Straight Dope that could be described as a mistake, although I wouldn't use so vulgar a term. You said the reason worms crawl out on the sidewalk when it rains is to avoid drowning when their holes fill with water. A few months ago, after the author of an article in Discover magazine made a similar claim, a scientist who studied worms wrote in to say worms can live underwater as well as in the dirt. They don't breathe as we do but get oxygen in some way that makes drowning an impossibility. He said the reason they come out was mating. --Brad Campbell, Seattle

Hmm. The wormologist in question is Richard Wahl of Shippensburg University in Pennsylvania. He writes: "Worms do not drown when it rains. . . . Worms of all kinds are highly susceptible to dessication [drying out]. They breed when it rains. They come out of the ground to find each other and to lie side by side in a mating posture, a difficult thing to do in the confines of their burrows. [And we complain about the back of a Ford!] The only time earthworms can safely come to the surface to breed is when the ground is thoroughly soaked.... Worms don't have lungs."

It is of course true worms don't have lungs. They breathe via gas diffusion through special organs in their skin. Cecil knew this. It is also true that the skin must be moist for this to work, just as the air sacs in our lungs must be moist. Cecil knew this too. But I had the idea that if the worm were completely immersed it would drown. Maybe not true. I have consulted with Charles Drewes, professor of wormology (actually, zoology and genetics) at Iowa State University, who tells me worms can survive for long periods underwater.

You're now thinking: Why take some expert's word for it? Why not perform certain obvious experiments and find out for yourself? Well, I couldn't. The Straight Dope lab was being used to bake a cake. Besides, how much do you think they're paying me that I should spend my time drowning worms? Be that as it may, we are still faced with the question of why worms crawl on the sidewalk after it rains if they can't drown. With all respect to Professor Wahl, I would venture to say the answer is: the rain gives them (the worms) a chance to get out of the house.

We know that worms will dehydrate and die if exposed to dry conditions for even a few hours. But they do need to leave their burrows once in a while, either to find new quarters when the old neighborhood gets crowded or do the wild thing (for a worm) with members of the opposite sex. Usually the only safe time to do this is at night; that's why they call them night crawlers. But worms can also do it when the ground is soaked after a heavy rain.

One last question now nags at you: Why are we wasting so much time on this? Look, I'll have you know that world- historical genius Charles Darwin devoted an entire book to it. OK, to worms, not to why they crawl on the sidewalk after it rains. But he did write: "After heavy rain succeeding dry weather, an astonishing number of dead worms may sometimes be seen lying on the ground.... It is not probable that these worms could have been drowned, and if they had been drowned they would have perished in their burrows. I believe that they were already sick [perhaps due to parasite infestation], and their deaths were merely hastened by the ground being flooded."

Charles wrote this in 1881. I am way behind in my reading.


Regarding what to do when traveling between countries that drive on opposite sides of the road [September 23]: I once knew a Norwegian who was a student at Oslo U. When he drove home the road passed several times in and out of Sweden, which until around 1965 drove on the left, while Norway drove on the right. The border was and is unguarded and in many places unmarked. The road was fairly narrow, and there was a tendency to drive down the middle, especially late at night when there was virtually no traffic. Now picture this: you are driving down this road, probably half asleep, you don't know and don't much care which country you are in and suddenly you see a truck bearing down on you. What do you do? --Michael Barr, Montreal

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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