Sometimes, you can see a lot by just sitting down.
I carved out some time in the field last Friday to collect data on poison hemlock in our research plots. After finishing that, I had about half an hour before I needed to head back to the office, so I took my camera for a walk along the creek running through our Platte River Prairies. Not having a particular agenda, I stopped to look at a tree that had been recently felled by beavers.
This tree, cut down by our local beavers, had sap seeping from the stump last week. The Nature Conservancy’s Platte River Prairies, Nebraska.
As I was admiring the patterns of tooth marks on the stump, I noticed an interesting-looking little fly hanging around. As I watched, the fly started to feed on the sap that was oozing out of the tree. Taking advantage of the fact that the fly was distracted by its meal, I managed to get a couple photos of it.
This fly seemed to be enjoying its meal enough that it didn’t mind me sticking my lens in its face.
Since I had time, I decided to sit and watch the fly for a bit. Before long, another – different – fly came along.
A second fly joins the meal.
One of my favorite statistics is that there are more than 37,000 species of flies in North America. That seems an almost unfathomable diversity. Taking that into account, I guess I shouldn’t have been surprised to see a third kind of fly arrive at the stump…
Fly #3. A big one with blue and green stripes on its abdomen.
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A rear view of fly #3, showing the striped abdomen.
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A tiny chalcidoid wasp was on the stump as well, though not feeding on sap (thanks to Mike Arduser for identifying it for me – Mike says they are a group of parasitic and important wasps). The quality of this image isn’t very good – my excuse is that the wasp was BARELY 2mm LONG and I had to crop it quite a bit so you could even see it…
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A tiny red mite came ambling along too… It was about the same size as the little chalcidoid wasp
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Fly #3 apparently didn’t like Fly #1 working over the same puddle of sap. This photo captures Fly #1 rearing back as Fly #3 lunged at it.
I wish I’d had more time to stick around; it would have been fun to catalog all the little critters that visited – or were living in – that beaver stump. I also wish I would have gotten a shot of the little wolf spider hiding in the pile of wood chips at the base of the stump – it darted out and almost caught one of the flies when it landed nearby, but didn’t stick around for a photo. Too fast for me…
I think my short time watching the beaver stump brings up a number of interesting points that I could focus on as the overall theme of this blog post. I could focus on the odd side benefits provided by the work beavers do. I could focus on the crazy diversity of life found on a single tree stump. I could focus on the way creatures of all different kinds are able to take advantage of unexpected resources (like oozing tree sap) when they appear.
But I think the biggest point is this: You can see and learn an awful lot by just sitting down and watching.
The Prairie Ecologist 
Fun post. Dr. Betz always advocated for somebody to start studying the prairie flies. Somebody! Please! Anybody! Flies! Many of them are pollinators. Many of them have amazing life histories. Bees have been getting a bit of traction. But flies? Please!
Couldn’t agree more. Flies need some positive press.
“You can see lots of things if you just look.”
-Yogi Berra
Great Work Mr. Helzer!
Great E.O. Wilson moment! Thank you for sharing.
I read your column just after spending 20 minutes in my wild urban garden and realized I had been out there looking around without actually being mindful of what I was looking at. No telling how much I missed in that 20 minutes of opportunity. Our garden has been pesticide-free for 25 years and is a rich biosphere with life ranging from English sparrows to yellow-crowned night herons, carrion flies to butterflies, geckos to fence lizards, fox squirrels to roof rats, honeysuckle to poison ivy, hackberries to Mexican plums, etc. Every day, just from my kitchen window, I see marvels, if I just take the time to look. Thanks for reminding me.
John – it’s ok to spend time outside without being constantly vigilant. (Unless you live near mountain lions) I wasn’t trying to imply that it’s not also acceptable to just sit and quietly enjoy the day! : )
Sounds like you have a great garden.
Thanks for your response. We believe it’s great, although our neighbors (in this lawn-worshipping city) may think it’s a jungle. I don’t think I’ll be led to obsessing, but thanks to you I do think I’ll be paying more attention to the flies! And to wondering about such things as the functions of a squirrel’s tail.
John
Taking time out to observe nature has it’s rewards :) and what a wonderful plug for the diversity of flies. Enjoyed your macro shots.
I was going to mention E.O Wilson saying that a person could spend a lifetime just studying the biodiversity of a single stump, but I think Patti beat me to it!
Hi Chris –
Every insect group out there in the prairie needs a lot more work to be well characterized and understood functionally, but flies are a particularly diverse lot, with perhaps a particular dearth of experts. I know a little tiny bit, to wit:
— I’m comfortable saying that fly #1 is Scathophaga stercoraria – Golden Dung Fly.
— Fly #2 is a blow fly, family Calliphoridae.
— Fly #3 is a different calliphorid. It’s “stripes” are its abdominal tergites, the hardened portions of each segment.
Even not knowing the names of flies #2 & #3, based on the scavenger/decomposer habits of the families involved, I’m fairly sure none of these is a prairie specialist, but rather, they are generalist species, like say, alfalfa butterfly, monarch, or pearl crescent among the “leps”. The specialists would be more likely to belong to the groups of flies that parasitize other prairie insects, or whose larvae live in leaf mines, galls, or other tissues of prairie plants.
I note by browsing in the fly section of bugguide.net that it reveals a large number of unidentified specimens compared to some other common insects. The mites are even more poorly represented with both images and identifications.
Thanks James! I had worked through bugguide and was thinking dung fly for #1 too – so it’s nice to have a second on that. I submitted photos of all three to bugguide but haven’t gotten a consensus on any of them yet. I also looked at mites on bugguide and gave up quickly…
I loved this post! The stat you gave regarding fly diversity just boggles the mind. Thanks so much for sharing.
Also… what lens were you using when you took these shot? They’re really great.
Hi Mike, Thanks. I used a Nikon 105mm macro lens.