Scientists decipher a wasp's way back home

Suppose you were blindfolded and dropped off in a strange place, will you ever be able to get back home? For us, the ‘intelligent’ Homo sapiens, the answer would depend on where you are stranded. If you are close to a human-inhabited region, and you possess certain technological devices, chances are high that you can return safely. But for the little Indian Paper Wasp, it seems that many of the foragers can return when displaced within a certain radius. This unique ability  has attracted scientists from the Indian Institute of Science (IISc), Bengaluru, to study the homing behaviour of the wasps. In particular, it is the ability of certain animals to navigate through unfamiliar areas towards a known territory.

The Indian Paper Wasp (Ropalidia marginata) is a social predatory wasp, which has a social structure involving one reproductive female (called the queen) and several non-reproductive females (or workers) in each colony. Widely distributed throughout India, this species attracted the attention of Prof Raghavendra Gadagkar and his lab members from the Centre for Ecological Studies at IISc. The insect has become the subject of many extensive studies.

Professor Raghavendra and his PhD student, Souvik Mandal have been closely studying  the homing behaviour of individual wasps, for the past five years. So, how do these insects find their way home? “As per current knowledge, they certainly use proximal visual cues of the landscape (possibly among many other environmental cues),” says Souvik. In one of the many experiments they conducted, the ‘foragers’ — wasps who brought in food — were collected and transported to increasing distances from their nests in a blindfolded manner in four directions with varying environments such as woods, rooftop, roads and industrial areas. A maximum of four wasps were released at pre-determined locations in all four directions at every 100 metre intervals.

On analysing the collected data, they found that almost all the released wasps returned to their nest on the same day of release when displaced within about 500 metre, beyond which, either they returned on later days or did not at all, in some cases. Joining the farthest release points from which all individuals returned on the same day of release, called the minimum homing distances gives the minimal homing area and it was found to be 0.73 km². And the farthest release points from which at least one individual returns, called the maximum homing distances, determine the maximal homing area, which was found to be around 6.22 km². This is a comparatively huge area for a wasp that measures about 1.5 cm in body length! What about the lost ones? It’s not really known, but they may start making a new nest on their own or they might find a new home!

The study of social behaviour of insects has far reaching consequences beyond just wasps. “Investigating on comparatively simpler neural mechanisms provides us knowledge about the basic necessities of animal navigation,” adds Souvik. What can the ‘advanced’ human race learn from the wasps? “The mechanism by which insects perform homing and navigation can be directly applied to robotics with simpler mechanism and circuits,” he states. The study might also be able to help in pest management. The paper was published in Journal of Comparative Physiology A.