These Wasps Remember a Friend's Face

Most people know the popular saying "an elephant never forgets." Past studies have shown that some birds have pretty awesome memories too. But what about insects? Now, new research has revealed that a tiny wasp species in the remote tropical forest of Southeast Asia tells friend from foe by recognizing them visually.

That's at least according o a study recently published in the journal Proceedings of the Royal Society B, which details how the wasp species Liostenogaster flavolineata is stunningly accurate at telling who belongs in their hive and who does not.

Many communal insect groups are at least somewhat capable of identifying an intruder. Using pheromones and noise signaling, insects can tell one another "hey buddy, were on the same team."

This has allowed some insects to develop impressive ways of ejecting unwelcome guests, with the members of one ant species literally throwing themselves from great heights with prospective invaders in tow.

However, smell (pheromones) alone doesn't always work. Two rival species of Pogonomyrmex harvester ants dwelling in deserts of Arizona and New Mexico, for instance, have made a living out of accidentally blundering into one another's hives. The two species smell so similar that siring males can find their way straight to a rival hive's queen unopposed. There, they will try to mate with the queen, only to realize last minute that they're courting the wrong girl. The result is that rival queens will try to "steal" the sperm of healthy males from opposing nests as frequently as possible to make more workers.

In the case of Liostenogaster flavolineata, however, such a scenario could never happen. That's because, according to Davic Baracchi, a researcher from Queen Mary University of London, these tropical wasps not only judge one another by smell, but by sight too, somehow recognizing visual cues on one another's faces that we as humans would never notice.

"Unfortunately neither sight nor smell is infallible, so they appear to not take any chances and attack anyone whose face they don't recognize," he explained in a statement.

It is only in the course of grappling that they can then get an accurate enough whiff to suddenly realize that they have their neighbor in a head lock.

According to the study, Baracchi and his colleagues only determined this after running a series of experiments with the wasps, depriving them of either scent or visual information. When the wasps could only see and not smell, the team found that they were more likely to attack a friend. Conversely, when they had only odors, they were far more likely to let an enemy in their ranks go unnoticed.

In this way, the researchers argue, the wasps may have adapted to err on the side of caution, relying most heavily on their eyes, and secondly on their noses for a thorough security check. (Scroll to read on...)

But why did these wasps pick up this skill in the first place? The researchers suspect that it may have had a lot to do with where they are found.

In the densely packed forests of Southeast Asia, these wasps are particularly prevalent, and pack into areas with hundreds of individual nests mere feet apart. To ensure that one 'borough' of this wasp city doesn't steal essential resources from another, the wasps found themselves needing a means for tighter security. Thus, sight recognition was born.

"These findings about individual face recognition in wasps add to a number of recent discoveries about the remarkable behavioral and cognitive sophistication in the tiny-brained social insects," added Lars Chittka, who authored the study.

Interestingly, it's not just insects that are surprising experts with a good memory for faces despite a tiny brain. Researchers also recently found that female guppies remember the face of their last mate, refusing to couple with males who look like their ex. You can read more about that here.

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