A rove beetle is a beetle with unusually short wing covers and a conspicuously long backside. If your first impression is that somebody stopped building it halfway through, you are looking at the right end.
There are many kinds. The one used for pest control in plant collections is Dalotia coriaria, a tiny hunter that spends much of its life in potting mix. Its appeal is simple: some of the insects bothering your plants spend part of their lives down there too. [1, 2]
A beetle with its wings tucked away
An adult Dalotia is roughly an eighth of an inch long, dark brown to black, with six legs and two antennae. Its short wing covers leave much of its segmented abdomen exposed. They do not mean it cannot fly. The flight wings fold underneath. [2]
Its young look different: pale, elongated larvae with legs near the head. They hunt before growing into beetles. That makes recognizing them useful. Finding one after a release need not mean you have acquired a new pest to research at midnight.
Same beetle, different stages
The larva is not a miniature adult. It grows through larval stages, becomes a pupa, and then emerges as a beetle. The larvae and adults hunt; the egg and pupa are developmental stages between the action. [5]
That explains why a population in the mix can include creatures that look unrelated. Only the adult has wings. The larvae stay on foot.
What happens in the pot
Fungus gnats are the obvious example of why a soil predator helps. We notice the flies. Dalotia encounters their larvae in the mix. It can also feed on shore fly larvae and thrips stages that enter that habitat. A beetle in the pot reaches a different part of the problem from a predator searching leaves. [2, 4]
This is the reason to consider rove beetles: you want a hunter working where those pests develop. A bottle of them is not a universal answer to anything crawling on a plant. Location is part of the job description.
A collection with persistently moist potting mix and recurring fungus gnat larvae offers a more relevant setting than a cactus pot that spends long stretches dry. And if thrips are feeding on the leaves, the beetles address only the stages they encounter below. The foliage still needs its own attention.
Are there rove beetles in the United States?
Yes. Rove beetles occur naturally here; they are not something that exists only in bottles. The family includes thousands of North American species with different diets and habits. An unidentified beetle from the yard is not automatically Dalotia, and an internet warning about another species is not automatically a warning about yours. [1]
If you found one unexpectedly, start with There's a Rove Beetle in My House. If you are choosing a beneficial, Rove Beetles Have Company explains what beetles add alongside nematodes and soil mites.
There is more going on than pest control
Dalotia also has an abdominal gland that makes a defensive chemical mixture. Researchers have used it to study how different kinds of cells evolve into a working organ. [3] That story gets its own space in Rove Beetles Come Armed.
You came for something to eat fungus gnats. Apparently it brought a chemistry department.
Sources and further reading
- University of Wisconsin Extension. Rove Beetles (Staphylinidae). Family identification and natural history.
- Cloyd & Herrick (2017). Ecology and Role of the Rove Beetle, Dalotia coriaria, and Insidious Flower Bug, Orius insidiosus, in Greenhouse Biological Control Programs. Advances in Entomology 5, 115-126.
- Brückner and colleagues (2021). Evolutionary assembly of cooperating cell types in an animal chemical defense system. Cell 184, 6138-6156.
- Pundt (2024 revision). Biological Control of Fungus Gnats. UConn Extension. Practical release and scouting guidance.
- Echegaray & Cloyd (2013). Life History Characteristics of the Rove Beetle, Dalotia coriaria, under Laboratory Conditions. Journal of the Kansas Entomological Society 86, 145-154.
