What are these ants doing?
February 25, 2017 11:45 AM   Subscribe

Please explain this ant (and other small insect) behavior I'm witnessing.

I am in Los Angeles, and the ants I will be asking about are what I would describe as the common house ant arount here -- small, brown, don't bite. Just your normal ant.

So I have a succulent plant that sends up shoots a couple times a year. The shoots have small pink flowers that must be rich in nectar, and the ants are all over them. The plant is right up against a window, so I have spent a bunch of time observing what's going on, and I am so confused about some parts! (Sorry I have no pictures -- everything I'm talking about is very tiny.)

1: The ants are grabbing the nectar. A long stream of ants goes toward the flowers. A long stream of ants goes away from the flowers, with their abdomens hugely full of what I'm assuming is nectar. It's clear. Their abdomens are so heavy they're dragging along the plant stem. When they get back to their nest, what do they do with this? Barf it up? Poop it out?

2: Sometimes I see one or more ants furiously banging their abdomens against the stem. These ants do not have an abdomen full of nectar yet. It's like a metal rock fan banging their head, only it's their abdomen. I assume they're communicating with the other ants. What are they saying?

3: Before the ants ever arrived, one frond of this plant was colonized by a mass of very small flying insects -- like gnats or no-see-ums. (I'm going to call them gnats because I lack another term.) They're extremely, extremely small. The ants don't appear to be eating them or fussing with them, but they're just all intertwined. The gnats just sit there and don't fly away, even when I blow gently on them. I very, very occasionally see one fly. I wondered if they're actually dead but their bodies are just sitting there. (Wouldn't they fall off or blow away if they were dead?) What's this about?

4: There's an accompanying mass of very small black things that look like a small sesame seed. I had started to assume that these were eggs of some sort -- I wondered if these were gnat eggs, and the gnats were hatching and then flying away when I didn't see them -- except some extra vigilant staring showed me that some of them move. THey have a few legs that are so small as to be nearly invisible. I sometimes see an ant furiously running its antennae over this creature. The ants never eat these (in front of me) nor do they pick them up or carry them. Ants will walk all over these little guys, but the little creatures hardly seem to notice or care.

5: Entire sections of this plant are solid black with a mass of ants, gnats and sesame-sized creatures. There also seems to be "mud" stuck in some spots of this plant, where the leaves meet the stem. It literally looks like very dark mud, except I know this plant isn't in a spot where it's been splashed with mud.

6: All of this is happening on a couple of this plant's fronds, which have maybe 10 flowers total. Other fronds of this same plant are bigger and have way more flowers, but the ants don't bother with those. There are new flowers blooming daily and the ants mostly ignore these. I might see one or two ants, vs. 200 on the main area.

Please explain this writhing mass of insects!
posted by BlahLaLa to Science & Nature (8 answers total) 14 users marked this as a favorite
 
Sounds like they're aphid farming.
posted by cosmicbandito at 11:55 AM on February 25, 2017 [9 favorites]


OH MY GOD. They're farming aphids. I had no idea. It isn't about the flowers at all. It's about the aphids and the honeydew.
posted by BlahLaLa at 12:05 PM on February 25, 2017 [6 favorites]


But if anybody wants to weigh in on some of the other stuff (abdomen banging, what they do with the honeydew when they're back at the nest, etc.) please do.
posted by BlahLaLa at 12:06 PM on February 25, 2017 [1 favorite]


The abdomen behavior sounds like "intracolony vibroacoustic signalling." What did the other ants do when some ants did this? Under what circumstances did you observe this belly-banging?

One thing to be careful of when you are watching ants quite closely is your breath: ants are sensitive to the carbon dioxide or moisture in your breath, and it alarms them. For some reason, they seem to think the mouth of a mammal near them is a hazard of some sort. Speaking as an observer of ants, nosebreathing is indicated.

Are you nearsighted, by any chance?
posted by the Real Dan at 12:18 PM on February 25, 2017 [3 favorites]


I am nearsighted, and I am watching them through the window. So I can get really, really close (because the plant is right up against the window) but they don't seem to notice my presence, and I'm not breathing on them.

I couldn't see if there was a specific response to the abdomen behavior. There are a lot of ants, and a lot of things happening at once.
posted by BlahLaLa at 12:27 PM on February 25, 2017


Entire sections of this plant are solid black with a mass of ants, gnats and sesame-sized creatures. There also seems to be "mud" stuck in some spots of this plant, where the leaves meet the stem. It literally looks like very dark mud, except I know this plant isn't in a spot where it's been splashed with mud.

Probably sooty mold or some variant thereof. It will feed off the sugar from the nectar either dropped by the aphids or seeping from wounds in the plant.
posted by srboisvert at 2:46 PM on February 25, 2017 [2 favorites]


Update: for about 6 weeks the aphid farm was going strong. Just hundreds of ants, and probably thousands of aphids. Then there was the addition of hundreds of small white things that looked like eggs. I figured it might be the next generation of aphids. But...shortly after that, the entire area cleared out. No ants or aphids left. A few of the white pods remain, each with a tiny hole -- something must've hatched.

Not sure why that happened, but it was fun watching it while it lasted.
posted by BlahLaLa at 11:10 AM on April 28, 2017 [1 favorite]


How sad!

I wonder if the hatching of the second generation of aphids triggered a migration. Like it signaled to the ants that the area around the nest was "farmed out" or something.
posted by tobascodagama at 11:42 AM on April 28, 2017


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