From Dr. Eleanor's Book of Common Ants
A.K.A.: Big-headed ant
Where it lives: Big-headed ants nest in rotting stumps, logs, and under rocks in forests and backyards. They also nest in open sandy ground.
What it eats: Dead insects and sugary substances. Big-headed ants also forage on human foods like peanut butter and tuna fish.
What’s the big deal?
Pheidole dentata are members of a group of ants called big-headed ants. Big-headed ants get their name from their dimorphic worker caste. That means they have two types of workers: small, regular-looking workers called minors and larger soldiers with whopping big heads called majors. Majors and minors are all sisters, and they’re all adults. Majors get their big heads because they were fed special food at just the right time when they were larvae.
Having big-headed sisters comes in handy when these ants are scavenging a meal or defending their nests. Majors’ big heads are packed with muscle, not brain, and these ants lend their extra brawn to help defend and carry food that is too big for minors and, in this species, to chomp down on intruders unlucky enough to stumble across their nest entrances.
When gatecrashers like fire ants approach this species of big-headed ants’ nests, minors recruit their major sisters to come barreling out of the entrance like juggernauts, biting and snapping their enemies to bits with their powerful jaws. Minors sometimes take advantage of their own diminutive size and hold down their enemies by the legs or antennae for their major sisters to turn their enemies’ bodies to scraps with their sharp mandibles. If the big-headed ants are outnumbered and are losing ground, they grab their larvae and evacuate the nest, running away in all directions.
While having all that brute force is helpful for keeping enemies at bay, big-headed majors are all thumbs when it comes to everyday chores inside the nest. Too big to feed larvae or take care of the queen, majors leave most of the housework to minors. Once adults, like many other social insect species, minors perform different duties as they age. When they are very young, they only take care of larvae and help the queen. As they age, they also help keep the nest clean by transporting trash outside the nest. Finally, they become foragers and nest defenders.
Researchers examining the heads of big-headed ant minors found their brains actually change as they get older. The part of their brain that stores their memory gets bigger around the time they become foragers. This helps big-headed ants to find their way back to the nest when they are out looking for food.
Big-headed ants eat everything from dead insects to sugary foods. Usually they stick to the great outdoors, but occasionally they make their way into people’s homes in search of food. Only then are they considered pests. Another species of big-headed ant, Pheidole megacephala, is invasive, often sneaks in to people’s homes, and is a major pest across the globe.