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Fig. 5. Time-compensated orientation of monarch butterflies having a 120° view
of the sky including the sun with and without occluded dorsal rim area (DRA).
(A) In 2003, control monarchs oriented in their typical
south–southwesterly autumn migratory direction. (B) Overpainting of the
DRA did not affect their ability to orient in the migratory direction. (C) SEM
image of the dorsal-most part of a monarch eye showing the extent of the paint
mask covering the DRA. Such images revealed that the 14±4 (mean
± S.D.; range 4–37) most marginal rows of ommatidia
were occluded in the dorsal half of the eye in the DRA-animals. Thus, the DRA,
which has a maximal width of three rows of ommatidia
(Labhart and Baumann, 2003),
was amply covered in all overpainted eyes. (D) In 2004, non-clockshifted
control monarchs showed an unusual mean migratory direction just east of
south. (E) Clockshifted monarchs shifted their orientation +96°. (F)
Clockshifted monarchs with their DRA occluded also shifted their orientation
clockwise (+86°) as predicted when they use a time-compensated sun
compass. For explanation of symbols, see legend to
Fig. 2.
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