Communal tank: Millipede and Harvestman interactions

[davehuth]

I don't sterilize my communal enclosure substrate for various reasons, and so I get interesting hitchhikers showing up occasionally. I watch the whole operation like a hawk and remove anything that makes me nervous (so far in 2018 a tiny centipede, and a couple ants).

Something I've been unsure about have been local harvestman species. I like what they add to the experience of watching the tank, so I've left them alone and watch them closely.

I see they eat dog food and veggies and rarely engage with other animals (or each other). They're opportunistic scavengers, but I know some species can have predatory behaviors. I may have to remove them as they grow (I worry about any baby millies I might get).

After about 6 weeks there've been no problems, but I wanted to ask the brain trust here if there's been documentation of them causing trouble for millipedes. The millies are the stars of the enclosure, though it also includes hisser roaches and fruit beetles.

I noticed one of the harvestmen giving attention to a few millipedes. I've seen them meet up at the supplemental feeding dish, and then the harvestman will start exploring part of the millipede exoskeleton. I can't always tell what it's doing, but at times its pedipalps are in contact with the exoskeleton. I know pedes can become stressed by persistent tactile stimulation, and once I saw a smaller Ivory recoil and retreat. But the harvestman didn't persist and the Ivory settled down quickly.

Interactions with the larger millipedes can last several minutes. I have a couple hefty Orthoporus (5+ inches long, and thick) who have been explored by harvestmen and seem to not notice (they continue eating or basking, don't recoil or react in any way I can see). What fascinated me most is that yesterday I saw clearly that the harvestman grabbed a mite from the exoskeleton of the millipede! It then moved away after no more than 5 minutes of interaction.

The purpose of the tank is to experiment with keeping inverts communally, and figure out good combinations of species and best practices for keeping them together in ways that allow individual animals to thrive. So when I notice something interesting like this, especially interactions between species, I want to ask for input in case others have encountered similar situations or have other knowledge to share.

I don't have photos of the harvestmen doing their business yet, but will add some to this thread as I'm able. Thanks!

 

[LawnShrimp]

I don't keep harvestmen but what they are doing to the millipede makes sense. Harvestmen eat protein-rich detritus but also like to feed on mites. It sounds like a good idea for keeping mite populations down.

What species of harvestman are you keeping? I might want to test this myself in case a mite outbreak happens.

 

[mickiem]

I don't even mix millipede species but it sounds like a lot of fun! I have been wanting to put together a display enclosure and put a variety of inverts in it to watch. You'll be the first to know when I do! @davehuth ps "brain trust". (I looked for an emoji brain wearing a hat, but there isn't one yet.)

 

[davehuth]

What species of harvestman are you keeping? I might want to test this myself in case a mite outbreak happens.

I have no idea! They popped out of the substrate as teeny babies (leaves and wood collected on the surface on my yard during below-zero temperatures this winter). As they've grown, they're clearly different species. Some even may be different genera - some have the long spindly legs, and some much shorter. One that hangs out on the dog food even drags its body along the ground rather than holding it aloft. So there's a lot going on in there, and I'm almost completely ignorant of the Order. I'll work at getting some diagnostic photos posted.

 

[davehuth]

I don't even mix millipede species but it sounds like a lot of fun! I have been wanting to put together a display enclosure and put a variety of inverts in it to watch. You'll be the first to know when I do! @davehuth ps "brain trust". (I looked for an emoji brain wearing a hat, but there isn't one yet.)

I'm having a great time with it. I've had a millipede expire for unknown reasons, and this has made me panic, but it was a wild caught purchase from ebay... hard to say how old it even was. However, this is the tank with Ivories that never show themselves, which I think is unusual for that species, so maybe there's something off. Narceus and Orthoporus seem equally happy, active, and fun. If those 2 different millipedes can keep it going together for any length of time then maybe anything's possible Everything's primed with spingtails, I have low-light houseplants growing, roaches don't bother anyone. There could be nightmares happening out of sight (beetles burrowing through moulting pedes or other horrors?), but the substrate is extra deep and extra rich, so maybe some kind of balance will be struck. Narceus are mating every night so seeing what comes of that will be a big step. I hope you give it a try, with your expertise we could learn a lot of information about how to pull this off

 

[davehuth]

Here are a couple of the Harvestman species in my communal millipede tank. There are 2 or 3 individuals of each of these two forms. A third possible species has eluded my camera, I'll keep trying. My ignorance far outweighs my knowledge of Opiliones, so I don't even know if these photos show proper diagnostic features. They're continuing to eat, moult, and grow, and I still detect no problems for the overall well being of the enclosure.

 

[Lithobius]

Looks like two different Eupnoi species, confident of that at least. A lot of Eupnoi look the same to me, Laniatores are my specialty
These guys are definitely different species, most likely different genera, potentially different families but my gut feeling says Sclerosomatid for both.

You caught a really good diagnostic character on the bottom one on the palp (that little indentation that makes it look kind of like a mitten). I'll look at some papers next week at work and get back to you on that one. I know it's a fairly common short legged species but I just don't know it offhand.

I think the top one makes me think of Leiobunum but there are quite a few similar ones with that saddle pattern. It could also be immature which makes IDs hard. Any closer pics of the top one's body would help (the legs aren't particularly diagnostic)


I'd like to get a few of these guys in my communal containers also, I have at least 3-4 species in my yard without looking particularly hard. Your idea of collecting substrate and seeing what pops out sounds fun.

 

[davehuth]

Looks like two different Eupnoi species, confident of that at least. A lot of Eupnoi look the same to me, Laniatores are my specialty
These guys are definitely different species, most likely different genera, potentially different families but my gut feeling says Sclerosomatid for both.

You caught a really good diagnostic character on the bottom one on the palp (that little indentation that makes it look kind of like a mitten). I'll look at some papers next week at work and get back to you on that one. I know it's a fairly common short legged species but I just don't know it offhand.

I think the top one makes me think of Leiobunum but there are quite a few similar ones with that saddle pattern. It could also be immature which makes IDs hard. Any closer pics of the top one's body would help (the legs aren't particularly diagnostic)


I'd like to get a few of these guys in my communal containers also, I have at least 3-4 species in my yard without looking particularly hard. Your idea of collecting substrate and seeing what pops out sounds fun.

Thanks so much for being so generous with your knowledge! I've never even once tried to identify one so I didn't even know where to start. I think it's likely these are juveniles as it's been fewer than 3 months. They're continuing to moult (right in the open where it's easy to see, which is really cool to watch!).

Knowing the palps are useful to see is helpful. They add a lot of interest to the enclosure, I like watching the long legged ones do their bobbing dance when I startle them with a flashlight while peeking in at night.

 

[Lithobius]

Thanks so much for being so generous with your knowledge! I've never even once tried to identify one so I didn't even know where to start. I think it's likely these are juveniles as it's been fewer than 3 months. They're continuing to moult (right in the open where it's easy to see, which is really cool to watch!).

Knowing the palps are useful to see is helpful. They add a lot of interest to the enclosure, I like watching the long legged ones do their bobbing dance when I startle them with a flashlight while peeking in at night.

No problem! At work I end up working with harvestmen quite a bit, but not local ones as much as I would like and always dead... I'm planning on fixing that soon! I'd love to get a few in my enclosures.
The other useful character is genitalia but obviously a living specimen isn't going to give that haha! For this group closeups around the eye / palp / chelicer region is really the best you can do with a live specimen. Either way juveniles and females are the hardest to ID so if they start changing color more dramatically post updated photos!

 

[davehuth]

You sound like you have a very interesting job!

Here's another view of Li'l Mitten-palps...

This evening a pretty orange long-legger appeared at the cup of roach chow. I think they just look amazing up close! ...