tiny curiosities

Cerastipsocus venosus ~ Bark lice

This last few weeks, I’ve been fairly busy photographing insects and trying to deal with all of the camera downloading, image sorting, backing up of drives, etc… that is associated with digital images. I see so many things that I’d like to share, but am never quite sure just how interesting these images are to others. Today’s offerings seem a bit on the unusual side – even to me – so I decided they were worth writing about.

Before I say anything more about the top photo, imagine a spot no larger than your thumbnail on the bark of a tree. Yesterday, I noticed such a spot a couple of inches above a tiny patch of lichen on a poplar along one of the trails here at the farm. As I moved in close to investigate, the spot began to move, morphing into a ring, and then moments later, reformed as a dense spot back in its original position. It was then that I realized that I was looking at some type of insects so small that I couldn’t really see what they might be. I shot a few photos and then viewed them on the LCD screen. Whoa! I discovered a herd of tiny creatures with bright yellow stripes around their abdomens! (click on all images for larger views). I’d never seen their like before, so I had to hit the books to try to figure out what I’d photographed. It turns out that they are Cerastipsocus venosus nymphs, commonly referred to as “bark lice”. They are considered beneficial bugs in that they feed on fungi, lichen and other organic materials. The adults are winged. Here’s a page containing information on a couple of species.

Misumena vatia flower crab spider killing stinkbug. Tiny fly atop the spider (probably some species of Milichiidae).

Recently, I’ve posted quite a few photos of Misumena vatia spiders, but this one is a bit different. Check out the tiny fly sitting on the spider’s back! I didn’t see it until I downloaded the photo and put it up on my screen. Once again, I had to get out my books and do some searching on the web to find out more. It turns out that there is a family of very tiny flies, the Milichiidae, some of which are kleptoparasites that hang out around predators such as spiders, assassin bugs, and robber flies. Some of these insects stake out a spot on a spider web so that they do a bit of scavenging. Others will actually sit atop either the predator, or the prey, waiting to move in for a meal. I suspect that’s just what this little fly is doing and that it must be some species of Milichiidae. When I began looking for info on these flies, I noticed references stating that these flies seemed to be particularly attracted to stinkbug prey (see the last paragraph on the page I’ve linked to). That’s of particular interest as that is just what this spider has caught. I don’t actually see that many stinkbugs being killed by flower crab spiders such as the above, and this is the first time I’ve seen one of these flies atop a spider, so perhaps there is a connection between these flies and stinkbug prey. In future, I’ll definitely be watching for these tiny scavengers.

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17 Responses to “tiny curiosities”

  1. Rebecca Clayton Says:

    Those are spectacular, as bark lice go. I think the tiniest insects are often the most intriguing, perhaps because they are so little-known.

  2. Wayne Says:

    The bark lice nymphs are amazingly patterned. I see that the adults still retain that appearance. Was the poplar one of the Populus species? It looks like they go for smooth-barked trees like crape myrtle and young oaks, down here at least.

    The little fly certainly must have been a surprise. Plus it allowed you to use the word kleptoparasite. I noticed earlier this spring that Lauxaniids feed on fungus and other accumulated detritus on leaf surfaces. I wonder if this little fly performs some function like that?

  3. robin andrea Says:

    Very cool bark lice. What a great pattern. Also a very interesting little fly on the crab spider. As Wayne noted, quite an opportunity to use the word kleptoparasite, a word I had not known before and am glad to be introduced to it.

    I’ve been going out daily to take a good look at our yellow yarrow, and so far have not seen any interesting bugs. I’ll keep my eye out for them, especially now since the sun has finally made a full and beautiful appearance.

  4. Dave Says:

    Fascinating stuff! I think I’m gonna include the bark lice in the Festival of the Trees.

  5. bev Says:

    Rebecca – Yes, quite true about very tiny insects being least known. When I was reading up on the Milichiidae flies, there were a couple of references to how little has been known of them until recent years. That makes it rather fun to study them.

    Wayne – It was the patterning of the bodies that really knocked me out when I first looked at the image on my camera’s LCD screen. They’re very neat. A few years ago, a friend in Texas showed me a photo he had taken of some winged insects on a tree in his yard. I didn’t recognize them, but now I realize they were the adult form of these insects. I’ll have to email him with the ID sometime. The tree was a Populus tremuloides, so yes, smooth-barked. The little fly was quite a surprise. When I look at that photo, I can’t help thinking how the fly seems to be watching the action. I can almost here him shouting, “Go get him, Tiger!” I guess that some of these flies actually scavenge spider kills.

    robin – I loved the pattern too. It seemed so improbable for an insect — certain patterns strike me that way. Kleptoparasite – I knew the word but have only heard of it in the context of certain insect parasites that hitch rides on the backs of carrion beetles.
    Glad to hear that you’re finally seeing some sunlight. Most insects love sunlight, so you should have a good chance for observations.

    Dave – Thanks! Please do include the bark lice in FOTT.

  6. Susannah Says:

    Hey, cool!

    I love those bark lice, and I’ll be looking more closely at tree trunks from now on.

    About those kleptoparasites, I discovered, a couple of days ago, a tiny yellow fly, like a fruit fly; red eyes and all, but yellow, hanging around my house spider’s web. I photographed it because it was pretty, but otherwise forgot about it. Today it was standing on a moth the male spider had captured yesterday.

    It is not one of your Milichiidae, since they are mostly black, but now I realize there may be more than a casual linkage between it and the spiders.

    The more we look at the tiny things around me, the more intriguing it gets, doesn’t it?

  7. bev Says:

    Susannah – I wouldn’t be at all surprised if that fly was a scavenger that hangs out around spider webs. And yes, there’s so much going on around us — small stuff that escapes our notice — but once you get in tune with it, there’s so much to see and learn about.

  8. neil Says:

    Bev- Thanks for solving a mystery for me. I’ve blogged about it over at microecos.

  9. Ontario Wanderer Says:

    Wonderful, wonder full photos, as usual. I am off to look for bark lice!

  10. DougT Says:

    I bet we have bark lice here. I’ve never looked for them before- now you have inspired me.

  11. Crafty Gardener Says:

    Fascinating insects. I’ll be on the lookout to see if I can discover any of the bark lice. It seems like I am like you, taking dozens and dozens of photos of interesting and unusual things in the garden.

  12. Clare Says:


    Reading your posts always makes me want to go for a walk with you. I’m continually amazed of just how much I’ve missed in the world around me.

  13. bev Says:

    neil – Great photos of the Green Lynx spider with the bee and fly.

    OW – Good luck finding bark lice. They’re quite small, but once you’ve seen them, they should be easier to find. However, take along your reading glasses as you’ll need them! (-:

    Doug – They’re very small, so I doubt most people notice them unless they were massing in huge numbers as in the photos on that web page I linked to.

    CG – Yes, it sounds like we’re doing the same thing — only “dozens and dozens” would be an understatement — it’s more like many thousands here at my farm! (-:

    Clare – Friends often tell me that going for a walk with me is fun — but we never seem to get that far. It’s not that I’m a slow walker, but just that there is so much to see that we don’t usually make much progress. If you’re ever down around Ottawa from spring through autumn sometime, do give me a call as we’re very close to the airport and there are plenty of trails to wander along.

  14. Stuart Says:

    Wonderful photos Bev, would love to see all the photos you don’t deem worthy to display on this site.

    I wonder what the evolutionary significance of the striping would be (if any) on something that small. They really seem to stick out like sore thumbs against the brown wood.

  15. bev Says:

    Stuart – Thanks! I take so many photos each day that it’s usually a bit of a decision to try to figure out which ones to write about.
    I do wonder about markings on very tiny creatures. You have to wonder how important those markings are, but perhaps to an insect that is seeing things at insect eye level, there’s a good reason for them.

  16. Cathy Says:

    I can imagine your delight with those ‘bark cattle’. I’m putting these on my ‘must find’ list along with the assassin bugs. But if this is the first time you’ve encountered them I’ll bet my chances are petty slim. This is really good stuff, Bev – and that stinkbug/fly on the spider’s back. Cool!

  17. bev Says:

    Cathy – I have vague memories of seeing these bark lice up at our cottage when I was a kid. Funny thing is, last night, I happened to look out the window and notice a conspicuous “patch” on the trunk of a large spruce tree that is about 3 feet from the house. I called Don to take a look, then reached out the window and touched the patch and sure enough, it was a large herd of bark lice massed on the tree. It may be that there’s a particular time when they are around and that this is it. I don’t know enough about them to know if that’s true, but I suspect so. Yes, for the little fly on that spider’s back. I still look at that one and think, “Wow! Look at that little dude!” (-: