Abstract
Insects inform themselves about the 3D structure of their surroundings through motion parallax. During flight, they often simplify this task by minimising rotational image movement. Coordinated head and body movements generate rapid shifts of gaze separated by periods of almost zero rotational movement, during which the distance of objects from the insect can be estimated through pure translational optic flow. This saccadic strategy is less appropriate for assessing the distance between objects. Bees and wasps face this problem when learning the position of their nest-hole relative to objects close to it. They acquire the necessary information during specialised flights performed on leaving the nest. Here, we show that the bumblebee's saccadic strategy differs from other reported cases. In the fixations between saccades, a bumblebee's head continues to turn slowly, generating rotational flow. At specific points in learning flights these imperfect fixations generate a form of ‘pivoting parallax’, which is centred on the nest and enhances the visibility of features near the nest. Bumblebees may thus utilize an alternative form of motion parallax to that delivered by the standard ‘saccade and fixate’ strategy in which residual rotational flow plays a role in assessing the distances of objects from a focal point of interest.
FOOTNOTES
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↵* Present address: Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Author contributions
All authors were involved in the conception and design of the project and in data analysis. O.R., N.H.I. and T.S.C. collected data. O.R. and A.P. wrote the MATLAB software. O.R., A.P. and T.S.C. designed and prepared figures. O.R. and T.S.C. drafted the text and it was revised by all authors.
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Competing interests
The authors declare no competing financial interests.
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Funding
Financial support came from the EPSRC, Biotechnology and Biological Sciences Research Council (BBSRC) and The Leverhulme Trust. O.R. was supported by the Overseas Research Students Awards Scheme (ORSAS) and a De Bourcier Doctoral Fellowship.
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Supplementary material
Supplementary material available online at http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.102897/-/DC1
- © 2014. Published by The Company of Biologists Ltd