Domatium

As temperatures begin to drop, many creatures search for winter shelter. That shelter may by your home, your gardening gloves, or, in some cases, a special sanctuary created by plants specifically for insects, spiders, and crustaceans. These tiny sanctuaries are called domatia.

Hairless domatium in a leaf (Melburnian) CC BY-SA 3.0

The word domatium comes to us from the Latin word domus, meaning home. It’s the same root used for words such as domestic and domicile. Domatia are chambers created by plants specifically for bugs. When similar chambers are created as a response to damage caused by insects, fungi, bacteria, nematodes, and other plants, those chambers are called galls. The difference between galls and domatia is a little fuzzy, as scientists learn more, but we will stick with the classic differentiation for our purposes.

Domatium description

There is a range of structures that can be called domatia. Most often, domatia often found inside thorns and on the underside of leaves. While these spaces are really tiny, so are the insects they house. And what could provide better shelter than under a leaf or inside a pokey thorn? These minuscule shelters may be nothing more than a small divot, surrounded by plant tissue or hairs, or they may be large, bulbous growths, filled with channels and chambers.

Mite inside domatium of camphor tree (Jsarratt) CC BY-SA 3.0

Which insects live in domatia?

Some plants have evolved to create these tiny homes for certain insects, in a mutually beneficial relationship that may, or may not, benefit your garden. Ants and mites are the most common domatia residents. While these pests suck nutritious sap from our plants, carrying disease with them as they feed, they provide their hosts with nutritious poop and a certain measure of protection from potential invaders. Plants that house ants are called myrmecophytes [MER-meh-co-fights] and the homes they provide are called myrmecodomatia [MEER-ma-COD-o-ma-she-uh]. Sometimes, unwelcome guests move in. Thrips are one example.

​So, grab a hand lens or a magnifying glass and take a closer look at all the amazing things going on in your garden!