What is a face? It is our identity; what we present to the world and where we express our emotions. Do insects have faces? I think most people would agree that they do, even if they are not the flexible mirrors of the soul that faces are in humans (and other mammals).

We humans have a remarkable capacity for memorising, or at least remembering, faces. Some people think that is why we evolved our large brains; or was it to impress the opposite sex with our phenomenal creative ability? Anyway, do insects recognise each other? Not just as a member of the same species, or gender, but as individuals? It turns out that some species can; but then again some can’t. It depends if they need to.

A paper wasp found in North America, Polistes fuscatus can discriminate between individual faces of their own species, but not those of other species (Tibbetts, et al.. 2021). They process the images of their faces in much the same way as we do, albeit through compound eyes. They have have extremely variable cuticular markings on the face and abdomen and they use these markings to visually identify queens and worker nestmates as individuals. The P. fuscatus queens are very adept at individual recognition, and can remember other individuals of the same species for at least a week.

Lead researcher Elizabeth A. Tibbetts realized that she could tell the unmarked wasps apart (by looking at the yellow, brown and black stripes and spots that make up their natural facial markings) and wondered if they could do the same?

“their brains learn reliable recognition by creating holistic representations of the complex images. They put features together to recognise a specific human face.” (Tibbetts et al., 2021).

However, when the researchers looked at some close relatives of of Polistes fuscatus (called Polistes dominulus and Polistes metricus) they found that they lacked facial recognition skills (Sheehan and Tibbetts, 2010). Why would one wasp be able to recognize individuals, but not others? Well, it seems that the P. fuscatus wasps have multiple queens and they all want to be the most dominant, “so being able to recognize each other helps them understand who’s already beaten who, who has higher ranking in the hierarchy, and this helps to keep the peace”  Elizabeth Tibbetts. In other words, the ability to identify superiors and subordinates – who’s who in the pecking order – in these hierarchical wasp societies is crucial. Reminds me of boarding school!

Those species which cannot recognise each other as individuals – P. dominulus (above) and P. metricus (below) – have little variation in colour patterns and live in single queen colonies. So because Polistes fuscatus are far more variable, with multiple queens competing for dominance, they have evolved robust long-term memories (Sheehan and Tibbetts, 2010).

Some wasps also use facial markings to decide if they like each other. Males of the Neotropical wasp Polistes simillimus have variable amounts of black pigment on their ‘faces’ (De Souza et al., 2014). These black patches are concentrated in the upper portion of the male’s head, around the ocellae (the three tiny eyes) (see below). In an experiment conducted in the laboratory, females chose males with a high proportion of black pigment on their heads as sexual partners. The amount of black pigmentation on the heads of the P. simillimus males is a a visual signal which the females are attracted to. Why? Because these ‘ornaments’ are signs of a high quality male.

A big black patch is probably an indication of the male’s wasps immune responses, longevity, fighting ability and nutritional status (de Souzaet al., 2021). I guess it is a way of showing that they are the top wasp?

One wonders what else can insects tell about each other from looking at their faces?

So when you next see a Polistes paper wasp (there are hundreds of different species), ask yourself – or better still ask the wasp🤣- is this a creature who can recognise and identify other individuals of her species? Or does it ‘just’ know how to recognise members of its own species, its own caste, its own colony and whether they are males or females.

More photos of Polistes fuscatus here, here, here and here.

References

de Souza, A. R., Júnior, C. A. M., do Nascimento, F. S., & Lino-Neto, J. (2014). Sexy faces in a male paper wasp. PLoS One, 9(5), e98172.

de Souza, A. R., Baptista, C. F., Nascimento, F. S., & Lino-Neto, J. (2021). The Choice of Sexual Partner in Social Wasps. In: Prezoto F., Nascimento F.S., Barbosa B.C., Somavilla A. (Eds), Neotropical Social Wasps, pp. 71-83. Springer, Cham. https://doi.org/10.1007/978-3-030-53510-0_4

Sheehan, M. J., & Tibbetts, E. A. (2010). Selection for individual recognition and the evolution of polymorphic identity signals in Polistes paper wasps. Journal of evolutionary biology, 23(3), 570-577.

Sheehan, M. J., & Tibbetts, E. A. (2011). Specialized face learning is associated with individual recognition in paper wasps. science, 334(6060), 1272-1275.

Tibbetts, E. A. (2002). Visual signals of individual identity in the wasp Polistes fuscatus. Proceedings of the Royal Society of London. Series B: Biological Sciences, 269(1499), 1423-1428.

Tibbetts, E. A., & Dale, J. (2007). Individual recognition: it is good to be different. Trends in ecology & evolution, 22(10), 529-537.

Tibbetts, E. A., Pardo-Sanchez, J., Ramirez-Matias, J., & Avarguès-Weber, A. (2021). Individual recognition is associated with holistic face processing in Polistes paper wasps in a species-specific way. Proceedings of the Royal Society B, 288(1943), 20203010.