Stethorus punctillum
A tiny, shiny black lady beetle about 1/16 inch (1.5 mm) long whose adults and larvae eat spider mites. Arbico says an adult eats more than 40 a day, and UC IPM says up to 75 for the genus. It is a predator of heavy infestations. It needs plenty of mites to stay and breed, so it goes on hot spots, not in as a preventive. Seven or more wild Stethorus species (UC IPM) already do this job outdoors across the US, and protecting them is often worth more than buying beetles.
At a glance
- Mode
- Predator — adults and larvae
- Size
- 1/16 in (1.5 mm); black, domed
- Rate
- 1–4 per 10 sq ft (Arbico)
- Temp
- 67–90 °F (19–32 °C)
- Humidity
- 30–90% (Arbico)
- Egg to adult
- 18 days at 70 °F (Arbico) to 3–4 weeks (UC IPM)
How it works
Adults fly in to mite colonies and lay their eggs one at a time on leaf undersides, beside the veins. The eggs are pale yellow to white, about 1/64 inch (0.4 mm) long, and darken before they hatch. Larvae are grey to dark brown at first, covered in branched hairs, and turn reddish before they pupate. They feed for 10–14 days. Both adults and larvae eat spider mites. UC IPM gives up to 75 mites a day for the genus, and Rincon-Vitova up to 100 for adults of the native S. punctum. UC IPM also says a female lays about 100–200 eggs over a life of one to two months.
The catch is appetite. A beetle that eats this much needs a lot of mites. Rincon-Vitova says the native species needs about 2–5 moving mites per leaf to keep its population going. Below that, the beetles leave or starve. That makes it a clean-up predator for dense colonies, and a partner to Neoseiulus californicus, which Cornell says works best released while mites are still few. Egg to adult takes about 18 days at 70 °F (21 °C) according to Arbico; UC IPM gives 3–4 weeks, and Rincon-Vitova an average of 23 days for S. punctum. It copes with heat and dry air: Arbico gives 67–90 °F, and says it survives above 100 °F outdoors.
Is it established?
What a working release looks like. Check the colonies you released on: the beetles stay only where mites are thick.
- WEEK 1Tiny black beetles moving through the colonies and webbing
- WEEKS 1–2Single pale eggs along the veins on leaf undersides
- WEEKS 2–3Grey, hairy larvae in the colonies, turning reddish as they grow
- WEEKS 3–4New adults, from about 18 days after the first eggs at 70 °F (3–4 weeks per UC IPM); mite colonies thinning
Release & handling
Adults are shipped overnight. Arbico says not to refrigerate them. If they must be held, it gives 73–77 °F and 60% humidity. Supply is seasonal: Arbico does not have beetles until late August or September.
Release promptly
Do not refrigerate. Hold at 73–77 °F and 60% humidity only if you must (Arbico).
On the worst colonies
At least 100 adults per hot spot, or 10 per infested plant (Arbico).
Weekly, 3–4 weeks
Arbico: weekly for 3–4 weeks; at its high rate, weekly until established.
Order ahead
Arbico lists it as unavailable until late August–September.
Pesticide sensitivity
In a 2025 laboratory study, abamectin was the most toxic of four miticides tested (ahead of pyridaben, spirotetramat and petroleum oil) to this beetle's larvae and adults. Petroleum oil posed the highest risk to larvae, despite its low acute toxicity. In a 2026 study on the related S. pusillus, broad-spectrum products harmed adults. These included acetamiprid, thiamethoxam, abamectin, fenpyroximate and cyantraniliprole. Selective miticides were largely harmless: clofentezine, hexythiazox, acequinocyl, bifenazate, spirodiclofen and cyflumetofen. Check a product →
When to choose something else
A heavy-hitting predator for dense colonies, sold by few suppliers and only for part of the year. Choose something else when:
- Mites are still few — Neoseiulus californicus works best released while spider mites are still low (Cornell)
- You need beetles before late summer — Arbico does not have them until August–September
- It is outdoors in fruit trees or the garden — wild Stethorus are likely already there; avoid broad-spectrum sprays and let them work
- The air is humid and mites are colonial under glass — the predatory midge Feltiella acarisuga is also sold for hot spots
Where to buy
Only one US retailer was found selling this species. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics100 / 200 adultsUS
Stethorus punctillum by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.