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First published online November 2, 2007
Journal of Experimental Biology 210, iii (2007)
Copyright © 2007 The Company of Biologists Limited
doi: 10.1242/jeb.013573
Inside JEB |
LOW LIGHT, BAD FLIGHT
laura{at}biologists.com
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It takes a pair of highly sensitive eyes to see well at night, although unfortunately for the nocturnal sweat bee, evolution messed up. These bees don't have the same eye type as other nocturnal insects, such as moths. In moth eyes, light is gathered from many different lenses and focussed on one photopigment containing structure called the rhabdom, increasing light sensitivity. Sweat bees rely on the same eye type as their day-active relatives instead, where the light from individual lenses is channelled separately onto individual rhabdoms. In the inky blackness of the Panamanian jungle, sweat bees likely rely on neural mechanisms in the brain that sum the signals coming from the eyes in space and time, making the visual signal stronger. At the darkest light levels, however, the bees' flight is likely to be much less precise.
To find out how light levels affect flight ability, Jamie Theobald and his colleagues illuminated the area surrounding 8 bees nests with infrared light, and then recorded their 3D flight trajectories using two cameras as the bees tried to land after foraging trips (p. 4034). The team found that in lighter conditions, the bees flew shorter and quicker routes to the nest entrances, whereas in darker light conditions, return trips were a mixture of both quick and slow. They found that in the darkest conditions, the bees flew passes as they approached the nest; sometimes they were successful on the first pass and found their target, while other times they flew many passes to reach their nest entrance. The nearer the nest, the slower they flew. By living in these dark conditions, the bees probably enjoy reduced predation and competition from other bees, but the light they fly in is so dim that they are likely flying to the limit of their visual ability, meaning that they often miss their target completely.
References
Theobald, J. C., Coates, M. M., Wcislo, W. T. and Warrant, E.
J. (2007). Flight performance in night-flying sweat bees
suffers at low light levels. J. Exp. Biol.
210,4034
-4042.
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