More than a decade ago, scientists demonstrated for the first time that insects are capable of facial recognition, after it was discovered that golden paper wasps are able to recognize other members of the same species based on their facial markings. Although it’s now known that several wasp species possess this ability, it turns out that one little wasp uses it as a way of determining friend from foe, alongside giving them a good old sniff, in order to protect against invasion.

Liostenogaster flavolineata, or the Malaysian hover wasp, is a social species found in tropical forests of South East Asia. Although individual nests built by this species tend to be quite small, they are often found in huge clusters consisting of up to 150 nests built in close proximity. This means that colonies are constantly faced with the threat of invasion from outsiders, who could sneak in to steal resources or even lay eggs.

In order to prevent this from happening, the wasps use two different strategies to discern colony members from alien intruders: facial recognition, or visual cues, and scent, or olfactory cues. Individuals from a particular colony will bear a certain chemical signal, or hydrocarbon profile, on their cuticle which can be used to identify members of their own species, colony and gender. Furthermore, each female also possesses a unique facial pattern. But why these particular wasps seem to use both, and whether they are used to the same extent, was unknown.

QMUL. Different facial patterns on female wasps.

To find out more, scientists from Queen Mary, University of London, traveled to tropical forests in South Asia to study the wasps in the wild. As described in Proceedings of the Royal Society B, the researchers carried out a series of tests on 50 different colonies found in Peninsular Malaysia. To examine their response to only visual cues, the researchers dangled lures close to a nest which consisted of a captured wasp, either from the same colony or a different colony, which had been stripped of its scent. To investigate only olfactory cues, the researchers dangled bits of paper that had been drenched in the scent of wasps either from the same colony or from an alien colony.

Interestingly, they found that these two different senses are not equally efficient in the discrimination of colony members from intruders. When only visual cues were available, the wasps were more likely to make an erroneous attack on a nest-mate; however, they quickly backed off once they realized their mistake and did not seriously harm the wasp. When presented only with scent, the wasps were more likely to accidentally accept an intruder.

When both cues were available, the wasps tended to ignore odor in favor of facial recognition, immediately attacking any wasp with an unfamiliar face. According to the researchers, this strategy is likely the safest since the wasps can judge the face of another wasp at a distance, but detecting scent requires them to be in close proximity to one another.

[Via Proceedings of the Royal Society B, Queen Mary, Science and Discovery News]