Bug o’the Week – Carpenter Ants

Howdy, BugFans,

The BugLady lives in a log cottage that’s rough cedar on the inside (think splinters), so when, one night, this Carpenter ant queen dropped down from the ceiling onto a book she was reading, she may have overreacted a tiny bit, and the ant met with an unfortunate accident.  Here’s a healthier individual https://bugguide.net/node/view/787312/bgimage. (Thanks to honorary BugFan PJ for confirming the ID)

Disclaimer: the BugLady doesn’t give advice on insect control or eradication.  That being said, if you see carpenter ants in your house, or if you hear the faint, rustling sound of chewing (it’s been likened to cellophane crinkling), get help.

Carpenter ants (called “sugar ants” in Australia) are in the ant family Formicidae and the genus Camponotus (which means “flat back”).  There are about 1,000 species in the genus worldwide – 50 in North America – and since the BugLady doesn’t know which species she had, the term “carpenter ant” here is generic.  They’re usually found where there are trees, but some nest in soil and others enjoy grasslands and even deserts.  They’re active all year round in warmer climates, but here in God’s Country, they enter a state of suspended development called diapause in the winter (unless they’re in the walls of a heated dwelling).

These tend to be large ants, and depending on species, they come in black, yellow, red, or brown, as well as two-toned.  They’re called polymorphic (“multiple-forms”) because there are three sizes of workers https://bugguide.net/node/view/729102/bgimage – minors, medias, and majors – plus large queens and half-sized males.

Like other communal insects, carpenter ants have a complex social system.  A queen mates with as many males as possible during her nuptial flight and uses that stored sperm for the rest of her life, which can be as long as 15 years.  She seals herself into a small cavity in wood or under bark and lays about 20 eggs.  When they hatch, she nourishes the larvae herself, using her fat reserves and protein from her wing muscles, and when they emerge from their pupal cases as adults, these new workers break out of the chamber and take over the nest duties https://bugguide.net/node/view/636620/bgimage.  The larger workers are guards and foragers; the smaller ones excavate and tend to the nest and care for the queen and the nursery (they feed their charges by regurgitating food – trophallaxis).

She lays eggs twice a year.  Some of the early spring eggs, specially nurtured, will become winged, fertile, royal ants (swarmers), and the rest are workers.  The late summer eggs produce workers that emerge the next year.  A nest usually doesn’t produce its first swarm until it’s three or four years old and contains several thousand ants.  A thriving carpenter ant colony often includes a parent nest and one or more satellite nests.  The parent nest is humid, excavated in damp wood, and the ant eggs need this high humidity.  Once the eggs hatch, the workers tote the larvae to satellite nests where the humidity is lower.

What fuels carpenter ants?  They’re omnivores and scavengers and sometimes predators, but the wood they chew is not a part of their diet (unlike termites, they don’t have the proper gut flora to digest cellulose).  Workers mostly eat carbs – sap, fruit, the liquid from extrafloral nectaries (https://uwm.edu/field-station/ants-in-my-plants/), (and discarded candy https://bugguide.net/node/view/1911307/bgimage), and they farm aphids, scales, and treehoppers https://bugguide.net/node/view/1537739/bgimage for the sweet honeydew these insects excrete.

The developing larvae require protein, which workers collect in the form of dead (and sometimes live) insects https://bugguide.net/node/view/957396/bgimage.  When they find one, a group may gather and carry it back to the nest, or they may eat it on the spot, carrying the nutrients back in their crops, and leaving the shell behind.  They usually forage at night.

When they have a long-term food source (like a herd of aphids) carpenter ants lay a pheromone trail for their sisters to follow, and they may use underground tunnels to get to their food source, too.  They can go without food for six months, but they may respond to a food shortage with a little cannibalism.

Who eats carpenter ants?  People do, for one.  The adults and larvae are eaten around the world, and Wikipedia tells us that in the early days of this country, lumberjacks in Maine ate carpenter ants to prevent scurvy.  We share them with wildlife like bears, skunks, big brown bats, salamanders, songbirds, wild turkeys, and, famously, Pileated Woodpeckers.

Carpentry is their raison d’etre, and in their proper place, they are important decomposers (a study in the Northeast determined that 75% of carpenter ants are found in dead trees).  They tunnel in wood that’s been softened up a bit by moisture (an important thing to remember if you’re trying to avoid carpenter ants in your walls), and their tunnels open up a decaying tree to more moisture and to fungi.  They tear the soft wood with their sturdy jaws https://bugguide.net/node/view/1615668/bgimage forming long tunnels called galleries https://bugguide.net/node/view/1783110/bgimage.

The tunnels are clean and are sometimes described as looking “sanded.”  Wood shavings that result from their excavating, along with desiccated bits of food, and deceased ants are removed from the tunnels – dumped out of a hole in the trunk that’s sometimes called a “window.”

Fun Carpenter Ant Fact: when the workers are alarmed, they may warn their sisters by whacking their mandibles and abdomen against the inside of the tunnel walls, making a loud sound that is sometimes audible even to us.

Another Fun Carpenter Ant Fact: they are gentle souls that would rather live to fight another day, but if they are mishandled, they will bite (painfully) and then squirt a little formic acid into the bite for good measure.  They don’t sting.

BugFan Bill invites BugFans who would like to dive a deeper into the world of insects and insect issues to check out the Conservation and Ecology – Insects in the Midwest Facebook group https://www.facebook.com/groups/183261300269413.

Kate Redmond, The BugLady

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