October 14, 2016
Ants on the Move
Even though temperatures this fall have been mild, seasonal changes are occurring all around us. The increasingly shorter day lengths have leaves turning color, and asters and goldenrods going to seed. Anywhere you see trees you’ll likely also see branches aflutter with migrating birds while, on the ground, scatter-hoarding squirrels and larder-hoarding chipmunks race each other for the choicest bits to stash away for later.
But these familiar activities, my “Good Natured” friends, are just a hint of the biological shifts that are going on right now as our wild neighbors prepare for the coming winter. Today, and in the coming weeks, we’re going to take a look at a few wildlife phenomena that, unlike a golden hickory leaf or a chattering flock of blackbirds, might easily go unnoticed.
The first observation I’d like to describe comes courtesy of our nature school program team. A week or so ago they were conducting forest ecology classes for fourth-graders at Delnor Woods Park and happened upon a strange site: a mass of ants skittering about a moss-covered log.
Some were golden yellow; some were dark – almost black. Some were larger; some were smaller. Some had wings; some did not. This intriguing diversity, combined with the ants’ frenzied movements, made for a very compelling – and picture-worthy – scene.
I wasn’t there to witness the spectacle, but looking at the photo and hearing the eyewitness accounts, I think I can make a pretty good guess at what was happening.
Ants, like most other creatures, and plants, too, for that matter, have a need to disperse. If they didn’t, they’d soon overcrowd an area, deplete its resources and trigger an unceremonious population crash. Dispersal allows species – and, yep, humans are included in this broad generalization – to spread their genes to new territories, and, with luck, find conditions that will be favorable for future growth.
The Delnor Woods ant colony had spent the past several months taking full advantage of our wonderfully warm, wet summer, and now it was, to paraphrase an REO Speedwagon song, time for them to fly.
Most ant species, at some point during their colonies’ cycles, will raise a generation of individuals known as alates. Lexophiles will recognize that word’s root, ala, as Latin for wing. Alates, which consist of reproductive males and females – future colony queens – shoulder (or is it thorax?) the heady responsibility of dispersing to new locations and allowing the species to carry on.
The smaller winged ants were males, whose attendance at this momentous event would be brief but essential. Their one job was to mate with the queens, which would then take off for destinations that will be advantageous for future colonies.
Although we can’t say exactly where the Delnor Woods queens were headed, I’m going to once again apply some (very slightly) educated guesses to complete the picture, so to speak. The ants in the photo look to me like citronella ants, Lasius claviger. A few other types of ants look similar to these guys, but having encountered L. claviger at Delnor Woods in the past, that’s the species I’m gonna go with.
To be absolutely certain, though, I would have had to have been there, and taken a sniff. That’s right – one of the key identification characteristics for L. claviger, as indicated by the “citronella” in its common name, is a lemony citrus odor.
At any rate, if we move forward with the assumption that the Delnor ants were indeed of the citronella variety, we could then also deduce that the new queens were heading off in search of other ant colonies, usually another species of Lasius, which they will then take over by killing the reigning queen. Having mated before leaving their natal colony, the claviger queens can then begin to populate with members of their own species, eventually creating a colony that is 100 percent claviger.
The teachers and students who witnessed the claviger activity at Delnor Woods were lucky indeed. Citronella ants carry out most of their activities underground, deriving their nutrients from aphids that are in turn feeding on plant roots. About the only other times I’ve encountered the species, and their wonderfully lemony smell, is when I’ve been peering under logs and, once, when digging in my parents’ backyard.
October typically is the time that our local citronella ants take to the air. If you feel like you’ve missed them, mark your calendar for this time next year, when another batch of new citronella queens will be heading out to seek their fortunes.
If, however, you’re merely seeking more info on obscure seasonal changes, check this space again next week. You won’t be disappointed!
Pam Otto is the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-513-4346, potto@stcparks.org or editorial@kcchronicle.com.
Large winged females, smaller winged males and wingless attend-ant, haha, workers make preparations for future generations of Lasius claviger – the citronella ant. These ants, though rarely seen, can be identified by the lemony scent of their namesake aroma.