Reference:
Queller, D. C., Zacchi, F., Cervo, R., Turillazzi, S., Henshaw, M. T., Santorelli, L. A., & Strassmann, J. E., 2000. Unrelated helpers in a social insect. Nature, 405(6788), 784-787.
URL:
https://www.researchgate.net/publication/12453010_Unrelated_helpers_in_a_social_insect