The Dual Function of Orchid Bee Ocelli as Revealed by X-Ray Microtomography

Research output: Contribution to journalArticle

Abstract

Visually guided flight control in the rainforest is arguably
one of the most complex insect behaviors: illumination
varies dramatically depending on location
[1], and the densely cluttered environment blocks
out most of the sky [2]. What visual information do
insects sample for flight control in this habitat? To
begin answering this question, we determined the visual
fields of the ocelli—thought to play a role in attitude
stabilization of some flying insects [3–5]—of
an orchid bee, Euglossa imperialis. High-resolution
3D models of the ocellar system from X-ray microtomography
were used for optical ray tracing simulations.
Surprisingly, these showed that each ocellus
possesses two distinct visual fields—a focused
monocular visual field suitable for detecting features
elevated above the horizon and therefore assisting
with flight stabilization [3–5] and, unlike other ocelli
investigated to date [4, 6, 7], a large trinocular
fronto-dorsal visual field shared by all ocelli. Histological
analyses show that photoreceptors have
similar orientations within each ocellus and are likely
to be sensitive to polarized light, as in some other hymenopterans
[7, 8]. We also found that the average
receptor orientation is offset between the ocelli,
each having different axes of polarization sensitivity
relative to the head. Unlike the eyes of any other
insect described to date, this ocellar system meets
the requirements of a true polarization analyzer
[9, 10]. The ocelli of E. imperialis could provide
sensitive compass information for navigation in the
rainforest and, additionally, provide cues for visual
discrimination or flight control.

Details

Authors
Organisations
External organisations
  • Australian National University
  • Diamond Light Source
  • Nelson Mandela Metropolitan University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Zoology
Original languageEnglish
Pages (from-to)1319-1324
Number of pages6
JournalCurrent Biology
Issue number26
StatePublished - 2016 May 23
Peer-reviewedYes