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Winter crane fly

Snow Flies

Source: Personal Observations

Read this and other stories in the book, Noticing Nature, by Chuck Bonner. Also available in e-book format for Amazon Kindle.

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I am in the process of "discovering" a new-to-me creature. Come, share the adventure!

For years, probably all my life, I've seen insects out in the middle of winter. Conventional thinking is that insects need warmth in order to function, that insects hibernate or die off in winter, only to reappear when the eggs hatch or the dormant individuals are reanimated by the warmth of a new spring. So, of course, I always thought that these insects in the snow were some kind of aberration. Maybe some slight warming spell had fooled the hibernating fly into waking up in the wrong season. These out-of-season insects, I assumed, were doomed.

And I never gave it much thought or paid any attention to these bugs.

Until one day late last fall.

I had set out for Arethusa Falls in a frigid dawn, temperatures barely above zero Fahrenheit. In the next couple of hours, the temperature climbed dramatically - surprisingly, really. By the time I was halfway back to the trail head at noon or so, I had removed my gloves and hat and a sweater. The temperature was just a little bit below freezing, but that was much too warm to be so bundled up while hiking.

And then I saw a bug.

Now, as I mentioned, I had seen bugs in winter before. It was common enough that I didn't think it all that strange, but uncommon enough to catch my attention.

And this time, I watched. And I noticed. And I thought about it.

The bug flew a short distance, landed on the snow and crawled for half a minute or so, then took off and flew out of sight.

If a bug can't fly when its muscles are too cold, how could this bug fly in subfreezing temperatures? And even if it somehow got warmed up, such as in a pile of composting leaves or something, how could it survive landing on the snow? How could it fly again after crawling on the snow for half a minute?

And if one of these insects had been fooled by this morning's rapid mid-winter warming, why not all of them? If an individual of this species was so easily tricked into breaking hibernation out of season, how could the species survive?

Clearly, this was not a mistake. Clearly, this insect was adapted to live in the cold. This was not some summer mosquito accidentally going out to die in the snow, but a creature that was perfectly at home in winter conditions.

The only odd thing, I thought, was that none of this had ever occurred to me before.

So, I took mental note of the habits and form of the insect in order to look it up when I got home.

It looked very much like a mosquito, but big. It was much larger than a typical female mosquito, perhaps five times as large, but nowhere near as large as the gigantic male mosquitoes I often see. It was about half an inch to three-quarters of an inch from its head to the end of its abdomen, and the wings, when folded over its back, extended some distance beyond the end of the body. It flew like a mosquito, beating its wings rapidly but progressing rather slowly.

I had no idea what species this bug was, and I knew very little of its habits, but I knew this: It was of the order Diptera (the same order that includes flies and mosquitoes), and it was adapted to be active in subfreezing temperatures in winter.

I couldn't find anything like it in my meager collection of books on insects, so I brought my research to the Internet. I found several articles about insects that are active in winter. There was a reference to a type of lacewing that comes out in winter. (I didn't pay much attention to this, and now I can't find it again!) I found articles about snow fleas (Hypogastrura nivicola) of the order Collembola, and Chionea, a genus of wingless flies in the order Diptera called snow flies. I was certain my "snow flies" were neither of these.

Now I began to doubt my observations. Maybe the bug reminded me so strongly of a mosquito that I only assumed it had two wings, or that its wings had the branching vein pattern of a typical fly or mosquito. Maybe it really was a lacewing, with four wings and a net-like pattern of veins in its wings.

Maybe I was mistaken. It's been known to happen. For instance, for years I had thought those mosquito-like bugs you sometimes see in winter had accidentally emerged from hibernation at the wrong season.

Soon it was Christmas. Amid the usual chaos - children and grandchildren coming over for dinner, got to peel the potatoes and help my wife set the table and all - I took a little break in Mine Falls Park.

When what to my wondering eyes should appear but a snow fly! This was exactly the same bug I had seen along the Arethusa Falls Trail less than two weeks earlier. It was the same size, it flew the same way, and it looked exactly the same. This time, the temperature was slightly above freezing.

I got as close as I thought I could without scaring it away. I took a good look. I took a picture.

Snow fly on snow

A fly standing on the snow on Christmas day in Mine Falls Park.

I took a movie. In this video (26 sec., 13 MB) you can see the "snow fly" sitting on the snow for a time, then flying away.

Yes, it had only two wings. Yes, it had the branching vein pattern of a true fly and not the reticulated pattern of a lacewing.

This was indeed a member of the order Diptera, and not the wingless "snow fly" Chionea.

The search had now grown more exciting. I didn't think this is a species unknown to science, because it is so easy to find and lives so close to human population centers. However, it is obviously little documented, and therefore it might be little known. I thought it might be possible that I can observe and record new information about this strange insect.

The next Saturday, I was off to Mine Falls Park again, only this time I was looking for snow flies. And did I ever find snow flies!

I took a few more still pictures, getting even closer than I had before. I found that the bugs don't scare all that easily, so my pictures show the classic Diptera features even more clearly.

Front view

A closer view of a snow fly in Mine Falls park.

Side view

What appears to be a straight stick or something is actually the bug's left legs. The foreleg
extends straight out in front, and the hind leg extends straight out behind. The right legs
are in the position you might expect, more out to the side.

I took some video (36 sec., 18.5 MB) of a "snow fly" walking on the snow. (Oh, the hazards the amateur nature videographer must face! While I was concentrating on documenting my new "discovery," my wife calls to tell me I should pick up some milk and bread on my way home. You can hear my phone in the video. She also told me she was going out with some friends, which was good, because in temperatures a few degrees above freezing, I was getting wet crawling around in the snow taking pictures of bugs, and this would give me a chance to dry my clothes before she found out.)

After taking my phone call, I continued recording the "snow fly." In this video (1 min. 30 sec., 47 MB), you can see the creature trying to take off a couple of times, but failing, then climbing into a rhododendron. Obviously, they are not quite perfectly adapted to flying in near-freezing temperatures.

A bit later, the "snow fly" did get off the ground. I took this video (52 sec., 27 MB) as it took off from the snow and flew to a granite boulder. I lost sight of it against the gray rock, but quickly caught it again as it flew up the hill and landed on the snow.

But the most amazing thing I saw that day was a group of at least half a dozen "snow flies" together. They were flying together near the ends of bare branches overhanging the frozen pond. They repeatedly made quick, straight vertical flights, followed by angled or spiral downward flights. Sometimes they seemed frenzied, and flew vertically up and down for very short distances. The whole display reminded me of the courtship displays of unrelated fireflies and the territorial/aggressive displays of equally unrelated dragonflies. You can see it in this video (43 sec., 22.5 MB).

That Sunday afternoon, I took a little hike on Pack Monadnock. I wasn't looking for anything in particular, just hanging out on a winter day in the woods. But you'll never guess what I found: A snow fly!

Again, it was exactly the same kind of insect. The temperature was only a little above freezing.

And I got my closest picture yet. The snow fly was crawling on the underside of a twig near the edge of a small cliff. I crawled out on a boulder near the twig. I was lying head downslope on an ice-covered rock at the top of a 20-foot cliff, balanced on my elbows so I couldn't work the manual focus of my camera, and the automatic focus kept focusing on the trees in the distance rather than on the snow fly. I put my left hand behind the bug to make the camera focus in closer, and that also provides some scale to the picture. And it's a good thing my mother wasn't watching.

Snow fly hanging on the underside of a twig

This close view shows the structure of the snow fly very clearly, and my hand behind it for scale. My hand was closer to the insect than the length of its body.

It could hardly be clearer. This is a Diptera. You can see the two wings. You can see the branching vein pattern in the wings. You can see the little round sucker-like mouth. (Maybe you'll need the full-size version of the picture to see that. Left-click the picture to view, right-click to download.) This is obviously a true fly and not a lacewing.

Here is a video (38 sec., 19.8 MB) of the "snow fly" taking off from the snow and landing on the twig in the photo above. And this video (35 sec., 19 MB) shows the "snow fly" crawling along the twig with my hand behind it.

Most recently, on New Years Day, I saw a "snow fly" flying through a rather heavy snowfall in Mine Falls Park, but I didn't get a picture or a video of it. Again, the temperature was just a little above freezing.

I'm still researching this strange insect, but it's gone well beyond searching on Google. I've reached the point of finding the e-mail addresses of entomologists whose expertise and specialty seems relevant, and hoping for replies to my inquiries. And it's starting to work.

Two entomologists have told me that my descriptions sound like a "winter crane fly" of the family Trichoceridae (and one of them confirmed this after looking at my first photo). Now that I know what to look for, I have found some information about this family on the Web. It's a little thin, but I should be able to make some progress.

I'll keep reading about the family Trichoceridae in my copious spare time and see if I can identify "my" snow fly by species (either the singular species it is, or the plural species, one of which it might be).

And who knows what will happen after that? Maybe I'll find that "my" snow fly is not very well known, and some entomologist will learn something new from my pictures and videos. Maybe I'll find that these snow flies are well known to entomologists and my pictures and videos are of no interest. In either case, I have learned something new to me, and I will continue to learn about what these strange bugs are. And that's a lot of fun!

I'll keep you posted.

Epilogue: If you have a valid scientific interest in obtaining a DVD of the full-resolution version of the videos linked on this Web page, please send me an e-mail using the feedback form below. Bear in mind that A) The best pictures and videos I have of these insects are those that are already linked on this Web page, although I do have higher resolution versions of the videos, and B) I'm not making an offer to send a free DVD to everyone who pretends to be an entomologist, but if you have a valid scientific interest, I'll see what I can do.

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