Volume 26, Issue 10, Pages 1319-1324 (May 2016) The Dual Function of Orchid Bee Ocelli as Revealed by X-Ray Microtomography  Gavin J. Taylor, Willi Ribi, Martin Bech, Andrew J. Bodey, Christoph Rau, Axel Steuwer, Eric J. Warrant, Emily Baird  Current Biology  Volume 26, Issue 10, Pages 1319-1324 (May 2016) DOI: 10.1016/j.cub.2016.03.038 Copyright © 2016 Elsevier Ltd Terms and Conditions

Current Biology 2016 26, 1319-1324DOI: (10.1016/j.cub.2016.03.038) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 The Prominent Ocelli of Euglossa imperialis (A and B) The head and ocelli viewed externally with scanning electron microscopy (A, inclined frontal view; B, dorsal view). (C–E) A 3D-rendered view of the ocellar structure from segmented computed tomography (CT) volumes (C; an orthographic projection of the ocelli from the direction of the aquamarine arrow in B; with inclined sections as indicated by the aquamarine lines in B; note that the right lateral ocellus is a mirrored copy of the left) and histological sections (D and E; vertical sections as indicated by the orange lines in B). Similar structural details can be seen in images from both CT and histology (color labels). Abbreviations: C, center; D, dorsal; L, lateral; M, median; O, outer; V, ventral. See also Figures S1 (for an interactive version of C) and S2 and Table S1. Current Biology 2016 26, 1319-1324DOI: (10.1016/j.cub.2016.03.038) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 The Focusing of Light onto the Ocellar Retinae (A) By looking through excised lenses of the lateral and median ocelli, we determined that the focal plane (at the back focal distance [BFD]) falls largely behind the retinae (upper and lower insets, respectively). Central areas of both retinae were predicted to be at the correct distance from the lens to receive focused light (dotted magenta lines, within BFD ± 10%), and additional areas were predicted to form a trinocularly overlapping visual field (orange lines; see Figure 3). The retinal color indicates the distance of the retinal surface to each lens’s rear surface. (B) Local distance of the front and rear (upper and lower lines, respectively) of each retinal surface to the rear surface of each lens, plotted along a transect beneath the midline of each ocellus, indicated by the black lines in (A). The intersection of the optical axis of each lens with its retinae is labeled with a colored dot in (A) and colored bar in (B). The asymmetry of distances beneath the lens of the median ocellar retina around its midline (and accompanying slight asymmetry of the focused retinal area and visual field) may be an artifact of the retina becoming slightly distorted during dissection. Abbreviations: C, center; D, dorsal; L, lateral; M, median; O, outer; V, ventral. See also Figure S3 and Table S2. Current Biology 2016 26, 1319-1324DOI: (10.1016/j.cub.2016.03.038) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 3 Mapping the Extensive Visual Field of the Ocelli (A–C) Ray tracing using 3D models predicts that the complete ocellar visual field is approximately hemispherical (solid lines denote borders of each ocellar field of view [FOV]; dotted lines denote where the focused areas of the retina receive light as in Figure 2, as mapped onto a sphere around the head in its approximate orientation during flight). (D) The visual fields overlaid on an upward facing panoramic image of a rainforest environment. The optical axis of each ocellus is denoted by dashed lines (A and B) or a dot (D). Note that the visual fields of the right lateral ocellus are mirrored copies of those predicted for the left lateral ocellus. See also Tables S3 and S4. Current Biology 2016 26, 1319-1324DOI: (10.1016/j.cub.2016.03.038) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 4 Evidence for Polarization Sensitivity in the Ocellar Retinae Transverse (A) and longitudinal (B) sections show that the rhabdoms of the ocelli have a straight rectangular cross section (4.4 μm long) that does not twist along the cell’s length. Photoreceptor rhabdoms have a similar orientation within individual ocellar retina (median ± SD in C), while each of the three ocelli has a different average rhabdom orientation relative to the head (D). Dotted extensions from the circles in (C) indicate the average orientation of rhabdoms in each ocellus, whereas the colored arrows indicate the average axes of polarization sensitivity (PS) for each ocellus. Current Biology 2016 26, 1319-1324DOI: (10.1016/j.cub.2016.03.038) Copyright © 2016 Elsevier Ltd Terms and Conditions