I was out in the yard with the dogs this afternoon, gazing at the wildflowers (weeds? no, wildflowers) growing on the periphery of the property, along the fence line. I spotted the white berries of a small red-twigged osier dogwood (Cornus sericea), but my eye was quickly drawn from the snowy fruit to the movement on the dark green leaves, many of which were oddly gnarled and curled.
Ants! Lots of them! Large black ones, but only partly black: the thorax was a deep shade of red. The ants seemed to be moving over these deformed leaves and their accompanying stems rather randomly, and without purpose. My first thought, given the numbers, was that they were tending aphid colonies, but no such colonies seemed to exist.
Neither did they appear to be foraging or actively feeding; their random ramblings simply took them across a leaf, then over then under again.
Their mandibles were, for the most part, open and looking like they would be rather pinchy should they make contact with silly human fingertips (so I kept mine at a safe distance).
Then I noticed this weird (in my experience anyways) behaviour:
(Sorry about all the heavy breathing, but it’s not mine…the small mugsly one was waiting – rather impatiently I might add – for her next frisbee toss).
Anyways. Did you see it? Look at the ant on middle of the leaf in the centre of the shot at about 0:15 for a pretty good example…although there are at least a dozen or so examples of the behaviour in the clip. It immediately brought to mind the “waggle dance” of their hymenopteran cousins, the bees. I have never seen this before, and I can’t find any good information about it other than a vague reference to a chapter in a book about communication in social insects. It seems to be a scraping-type of communication, where the tip of the abdomen is scraped on the substrate (in this case, the leaf) to create vibrations that can be picked up by other nearby ants. I have seen this in some caterpillars, but never in ants (if that’s even what it was).
Exactly WHAT these guys were trying to communicate, however, is beyond me. I’m hoping someone who knows a little about ants and stuff (or anybody else for that matter) might be able to chime in on this one…because it was pretty wicked-cool to watch.
So I went out yesterday morning, while it was still cool, to have a closer look at the dogwood plant. The ants were nowhere to be seen…until I started to handle the gnarled leaves. Then they emerged from within the protective coils and folds – cold, slow and sleepy – but armed with open mandibles at at the ready. I tapped one leaf sharply to dislodge the ants, then quickly plucked it from the stem. There had to be something more to this story…and there was:
Hidden on the underside of the leaf were numerous teeny-tiny aphids. Ah-ha! So now I understand the ants’ presence as well as their roamings over the leaves. I still am unsure how to interpret their communications, however. A few of my ideas: a “call to arms”, summoning other ants to a protective position in response to my presence and pokings; a friendly “hey, there’s some decent food over here”; or something being said to the aphids themselves perhaps? Something to stimulate their feeding and subsequent secretion of delectable honeydew? The plot thickens….
My fave antologist, Alex Wild, has provided some excellent information on both the identity and behaviour of these ants:
I can’t say I know for sure what the ants are doing. But I can tell you who they are: Camponotus noveboracensis, a carpenter ant species found in north temperate/boreal habitats across the northern tier of our continent.
Carpenter ants can communicate through substrate vibrations. One thing they do is spread an alarm signal by drumming their heads against the ground. They also do a simple vibration-type dance to recruit nestmates to food. You could be seeing either of both of those behaviors here.