Housefly and Pitcher Plant

2007 September 2

The Fly

The first picture I posted in the arthropod project was a blurry image of what was, probably, a housefly. Here is a much better picture, which even shows the wing veins, which make it possible for me to say that it is, probably, a housefly [1]

Well, obviously, since it was in the house, making a nuisance of itself, then of *course* it was a housefly. The only question is whether it is the “real” housefly, Musca domestica, or just some related fly that got into the house. I think it is the real thing, based on comparing some diagrams of wing venation that Bug Guide connected to, so we’ll go with it. Supposedly you can tell if it is male or female depending on the space between the eyes, but there are surprisingly few pictures of houseflies on Bug Guide[2], and I don’t really have much to compare it to.

So what is there to say about houseflies? They grow up in filth, spread bacteria and disease, annoy people and animals by trying to drink sweat and tears, then lay more eggs in more filth. About the best thing to say about them is that they promote elimination of filth, but there are lots of other organisms that do that. Oh, and also they provide nutrients for things like this:

The Fly’s Demise:

We were visiting a nearby lake (Lake Perrault), and noticed that a nice trail had been built to an adjacent small pond that was turning into a peat-moss-filled bog[4]. Right at the end of the trail, just a few feet from the viewing platform, was this beautiful example of a pitcher plant, Sarracenia purpurea. I had known that these existed in Michigan bogs, but I hadn’t realized quite what large plants they were; the flower stalk on this specimen was about two feet tall. It has the look of a tropical plant that somehow found its way into the frozen north.

The insectivorous portions are the leaves at the base, which are modified into tubular structures. Insects crawl in, can’t find their way out, and end up in the digestive fluids at the bottom that convert them into a nice, nitrogenous fertilizer.



This is important for the plant, because the stagnant little ponds that turn into acid bogs are notoriously nitrogen-poor[3]. By catching insects, the plant can extract nitrogen from the insect’s body proteins, fertilizing itself. They probably pick up a non-trivial amount of the other two critical fertilizer components (phosphorus and potassium) from this source as well.

While looking at the plant, we did actually see some flies that looked like houseflies land on the pitchers and go inside, never to be seen again. This suggests that the pitchers smell like decomposing filth, which would mean that nice, fat, juicy filth flies are probably the main thing that the plants eat.

[1] Oh sure, you may think that saying it is “probably a housefly” now is no better than saying it was “probably a housefly” then, so what’s the point of posting another picture? Well, first of all, this is a much *nicer* picture. And second, while I am still confused and uncertain, the confusion and uncertainty is on a much *higher plane*. That is, back then I was confused because I couldn’t even tell for sure if the wings *had* veins, or if there *were* eyes. Now, I can be confused because, while I can *see* the veins and the stripe between the eyes, I don’t necessarily know what they mean.

[2] This is one of the failings of things like Bug Guide that depend on random user contributions: people mostly take pictures of insects that are large, colorful, unusual, or otherwise striking. A housefly is none of these things. So, hardly any pictures, and the ones that are there, tend to be not the best.

[3] The nitrogen problem is the same thing that has driven so many of the insects that live in swamps and bogs to take up the habit of drinking blood. This leads to the situation where a biting fly might get a full load of blood from some hapless vertebrate, only to come back to the bog and get itself digested by a carnivorous plant. This is probably the only way that carnivorous plants would get any of their nutrition from human flesh, since even venus flytraps aren’t strong enough to bite off a chunk of you.

[4] The trail is part of the Michigan Nature Association’s Robert T. Brown Nature Sanctuary, which is centered around the little bog in question. The boardwalk was evidently just built by students and teachers from the Jeffers School

4 Responses
  1. Lyle Laylin permalink
    March 8, 2018

    Holy Cow!
    I’ve been looking in Michigan for Pitcher plants for years (not very hard)
    I may have walked right by while looking for a little bitty thing (like a Sundew )
    I’m absolutely going there this summer for a look.

    and for a diversion – Flies Eyes

  2. March 12, 2018

    Lyle: I just hope that they are still there (it has been awhile, these pictures are almost ten years old).

    That was an . . . interesting link. I don’t believe I ever heard anything by Heywood Banks before.

  3. Lyle Laylin permalink
    March 14, 2018

    The carnivorous plants are pretty limited as to where they will grow but they tend to be better at those environments than other plants, so once they have a spot they tend to stay there (at least according to what I’ve read)
    And honestly, another excuse to go somewhere new in the Keweenaw is always welcome.

    I first heard the song sung by a comedian who would wear a pair of “glasses” made out of strainers while he did it

  4. Lyle Laylin permalink
    June 24, 2018

    Thanks again for this post.
    I just got back from a visit to the Fen and got pictures of several different pitcher plants as well as some pink lady slippers which were also in bloom.

    I do hope the current lack of posts is solely do to you being very busy on other projects and we’ll see some new posts here in the future.

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