“It’s Round-up Time!”
The dark, deformed bud on the camellia caught my eye. All the other young leaves were unfurled and shiny bright green, but this one seemed withered, rather fuzzy, with a patch of mahogany brown.
I got up from lunch on the back deck to have a closer look.
An aphid ranch!
The bane of gardeners, aphids suck plant juices for a living. Aphids suck a lot of juice so, of course, they expel a lot of poop. Aphid poop (called “honeydew”) is sticky and very high in sugars processed from the plant’s juices. (“Frass” is the general term for insect poop.)
What insect is stereotypically fond of sugar, drawn to the sweets in our cupboards and at our picnics? Ants!
Some species of ants, often called “honey ants,” actively manage “herds” of aphids that supply them with honeydew for food. And there they were: a couple of ants were carefully walking or standing among the aphids amassed on the camellia twig, touching them with their antennae.
Honey ants touch their charges to move them, to care for them, to check their readiness, and to “milk” them. With the right stroking, a full aphid will expel a droplet of honeydew from its anus for the ant. The ant will take in the sweet drop and either digest it or take the liquid to the nest to share with other ants or with ant larvae. Although I couldn’t find out if our species does this, in some species of honey ants, “honey-pot ants,” individual ants gorge themselves with honeydew, expanding to become living storage vessels for the colony.
It’s a relationship that benefits both ants and aphids, for the most part.
The ants protect their charges from predators and groom them to remove parasites, and often move their stock to new feeding grounds as the old ones are depleted. I recall as a youngster watching ants in an apple tree wrangle their herd back to a good feeding site from their night-time shelter.
Some honey ants even gather aphid eggs at the onset of cold winter, taking them to safe shelter to start the next spring’s herd.
Aphids make pretty good livestock, actually. While there is variety among the large number of aphid species, aphids reproduce asexually for at least some generations: most females are born pregnant and the young are born live, looking like miniature adults. Nevertheless, under the right conditions there will be a generation with sexually reproductive adults that mate to exchange genes, and the females will lay eggs.
Further, aphids don’t generally run off. However, when conditions are right for a sexually reproductive generation of aphids, some adults will grow wings and fly away to establish new groups elsewhere. To combat this, some honey ants hobble their charges, removing the wings before the wanderers can escape.
Though my first impulse when I saw the mass of aphids was to dispatch the whole colony with a couple of squishy pinches, when I saw the hard-working honey ants, I decided to sacrifice a camellia twig for their husbandry.