# Arrhenotoky

> Reproduction in which unmated females lay unfertilised eggs that become males, while mated females make both sexes. Typical of spider mites and thrips.

- Canonical: https://genetixbay.com/knowledge/glossary/arrhenotoky.html
- Also written: arrhenotokous parthenogenesis, arrhenotokous
- Glossary category: Pests and diseases · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Arrhenotoky is a type of [parthenogenesis](https://genetixbay.com/knowledge/glossary/parthenogenesis.md) in which unfertilised eggs develop into males. A [spider mite](https://genetixbay.com/knowledge/glossary/two-spotted-spider-mite.md) or [western flower thrips](https://genetixbay.com/knowledge/glossary/thrips.md) female that has never mated still lays eggs, but all become sons; once she mates she lays mostly daughters. It is the reproductive face of [haplodiploidy](https://genetixbay.com/knowledge/glossary/haplodiploidy.md).

## In practice

For growers, arrhenotoky means a single female that survives a spray or arrives on a clone can found a population on her own, by producing sons and then mating with them. It is one reason quarantine and zero-tolerance clone policies matter: one survivor is enough.

## Don't confuse with

- **Thelytoky**: unfertilised eggs become females (some thrips; [aphids](https://genetixbay.com/knowledge/glossary/aphid.md) by live birth).
- **Haplodiploidy**: the genetic system behind it.

## Related terms

[Haplodiploidy](https://genetixbay.com/knowledge/glossary/haplodiploidy.md), [Parthenogenesis](https://genetixbay.com/knowledge/glossary/parthenogenesis.md), [Sex ratio](https://genetixbay.com/knowledge/glossary/sex-ratio.md)

## Read more

- [Temperature, humidity and pest population growth in cannabis: every major pest compared](https://genetixbay.com/knowledge/pests/temperature-humidity-and-pest-population-growth.md)
- [Spider mites on cannabis: life tables, ID and IPM](https://genetixbay.com/knowledge/pests/spider-mites.md)
- [Thrips on cannabis: life table, temperature, scouting and biological control](https://genetixbay.com/knowledge/pests/thrips.md)

## Sources

1. UC IPM. Pest Notes: Spider Mites (Publication 7405). University of California ANR. https://ipm.ucanr.edu/PMG/PESTNOTES/pn7405.html
2. Grbic, M. et al., 2011. The genome of Tetranychus urticae reveals herbivorous pest adaptations. Nature 479:487-492. https://doi.org/10.1038/nature10640