You have spider mites, and the suggested predators include persimilis, Californicus, and Andersoni. Apparently the infestation comes with a vocabulary test.
All three can eat two-spotted spider mites, but they make their living differently. Persimilis specializes in spider mites. Californicus has a broader diet while retaining a preference for them. Andersoni is a broader generalist still.1 Those differences matter when the food on a plant changes.
Suppose spider mites become scarce. A predator tied closely to that prey has fewer options. Andersoni can use other small prey and suitable pollen, which may help support another generation between pest meals. The useful word is “suitable.” An empty houseplant leaf does not become a buffet because the mite has a broad diet.
That makes Andersoni interesting for more than the length of its prey list. To understand what it might do on your plant, we need to look at the small life happening underneath a leaf.
A whole life beneath the leaf
Its full name is Amblyseius andersoni. An adult is roughly 0.02 inch long: a pale, droplet-shaped mite. It searches the underside of leaves and can rest near vein junctions. 2
Life begins as an oval egg. A six-legged larva hatches, then develops through two eight-legged nymph stages before becoming an adult. The nymphs are immature mites, not a separate kind of organism. Each stage has to succeed before an egg can become another reproducing adult.
This is why finding a moving adult answers only part of the question. It tells you a predator is present. It does not tell you whether the plant is supporting the next generation. Food is one of the things that determines whether that happens.
Pollen can be more than a snack
Researchers raised Andersoni on spruce spider mites, a flat mite called Pentamerismus taxi, or Scots pine pollen. It developed and reproduced on all three, although population growth was higher on the prey diets.3 Pollen supplied enough nutrition to help make more mites.
That gives a broad diet its practical meaning. When one food becomes scarce, another may keep the population going. It also explains the limit: the alternative has to be present and nutritious enough. The pine-pollen result does not make every pollen equivalent, and the flat-mite result does not establish control of every flat mite found on houseplants.
A broad menu still comes with preferences
Having another food available can help the predator. It can also complicate our expectations of which pest it will eat.
In a 2025 laboratory choice experiment, Andersoni preferred two-spotted spider-mite larvae over western flower thrips larvae across the temperatures tested. The strength of that preference changed with temperature.4
So “can eat thrips” does not mean “will give thrips equal attention when spider mites are available.” A generalist has choices; it has not agreed to your priorities. Prey lists tell us what a mite can consume. Evidence of pest suppression on plants tells us much more about the job we want done.
A leaf is also somewhere to live
Food alone does not describe a home. Turn a leaf over and look at the veins, folds, and hairs. To us, these are surface details. To a mite, they are places to travel, rest, and lay eggs.
Some grape leaves have small tufts of hairs where veins meet, called domatia. In a potted-grapevine experiment, access to these structures supported Andersoni abundance, and the mites used them as egg-laying sites.5 A modest tuft of leaf hair was useful architecture.
The grapevine result explains why the plant itself belongs in the story. Two plants offering the same prey can still provide different living spaces. It does not mean every leaf fold has the same benefit, or that a hairy shelter solves dry air.
When you inspect your own plant, look for the live pests and then the leaf surface around them. Andersoni needs more than a name on a prey list. It needs a meal it can find and a place where the rest of its life can happen.
It can make other dinner plans. Your plant still has to have something on the menu.
Sources and further reading
- Walzer & Schausberger (2011). Sex-specific developmental plasticity of generalist and specialist predatory mites in response to food stress.
- Koppert — Amblyseius andersoni. Morphology, leaf habitat, and life stages; manufacturer reference.
- Puchalska and colleagues (2021). A Preliminary Assessment of Amblyseius andersoni as a Potential Biocontrol Agent against Phytophagous Mites Occurring on Coniferous Plants. Insects 12, 664.
- Wang, Sekiguchi & Hinomoto (2025). Impact of temperature shifts on prey consumption and prey preference of the predatory mite Amblyseius andersoni.
- Pozzebon, Loeb & Duso (2015). Role of supplemental foods and habitat structural complexity in persistence and coexistence of generalist predatory mites. Scientific Reports 5, 14997.
The photorealistic header and teaching illustrations were generated with AI; they are not field photographs. Illustrations enlarge and simplify organisms and scenes to explain the biology, and cannot identify a mite species.