It’s nice to see that caterpillars sometimes eat the weeds too. This mallow burr is a major weed here, and comes up on any disturbed ground. It gets up to 2 m high and has burrs that stick firmly to any fabric. Fortunately it’s relatively easy to pull, when young, but I was delighted to see some caterpillars helping me with the job.
This caterpillar is in my old school colours, too! Green, black and gold, and even the red head fits with the later addition of the red house.
Biological control is a sound principle for home gardens. It works on the principle that a system in balance doesn’t let any one organism get too numerous, as there will be predators that move in to take advantage of the resource. The best way to encourage biological control is to have as broad a diversity of plants and animals in the garden as possible. Using insecticides for instance tends to kill off both the target pest insect and the full range of other insects, throwing the ecosystem off balance. On the other side of the coin, a garden with a wide range of plants, some flowering, some making habitat, will tend to house predator insects ready to pounce on pests as they arrive.
Sadly there is a reason why weeds are weeds; these ones are successful by sheer number of seeds germinating, so the caterpillars haven’t been up to the job of cleaning up the mallow and have just done some modest munching. Good luck to them though. I wonder what type of butterfly they become?