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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 – the product of our intellectuality, 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 of these wasps has attracted scientists from the Indian Institute of Science, Bangalore, to study the homing behavior of the wasps – the ability of certain animals to navigate through unfamiliar areas towards known territory, or to its nest.

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 peninsular 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 extensive studies for more than three decades, to decipher the evolution of social life in insects.

Among many other ongoing research projects, such as understanding the mechanism of queen selection and altruistic behavior of worker wasps, Prof. Gadagkar and his Ph.D. student Souvik Mandal have closely studied the homing behavior 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 like olfactory cue)”, says Mr. Mandal on how the wasps find out its nest.

In one of the many experiments they conducted, the ‘foragers’ – wasps who brought in food and execute foraging solitarily – were collected and transported to increasing distances from their nests in a blindfolded manner in four cardinal 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 cardinal directions at every 100 m intervals.

On analyzing the collected data, they found that about all the released wasps returned to their nest on the same day of release when displaced within about 500 m, 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? Not really known, but they may start making a new nest on their own or they might find a new home! “We have seen wasps joining nests other than its native ones”, says Mr. Mandal.

The study of social behavior of insects has far reaching consequences beyond just wasps. “Investigating on comparatively simpler neural mechanisms, as the wasps have, provides us knowledge about the basic necessities of animal navigation and homing”, adds Mr. Mandal. 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 adds. In addition to providing cues on social evolution, the study might also help pest management. “Since the wasps are predators andprey upon larvae of other insects, many of considered as pests. Understanding the foraging and movement patterns of the wasps can help bio-pest management”, signs off Mr. Mandal.

 

About the paper:

The paper was published in the Journal of Comparative Physiology A and can be accessed at

http://dx.doi.org/10.1007/s00359-015-1019-2

About the authors:

Mr. Souvik Mandal is a Ph.D. student at the Centre for Ecological Sciences, Indian Institute of Sciences, Bangalore.

Email id: souvik@ces.iisc.ernet.in

Prof. Raghavendra Gadagkar is with the Centre for Ecological Sciences, Indian Institute of Sciences, Bangalore.

Email id: ragh@ces.iisc.ernet.in