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Antire£ection structures on eyes potentially increase visual e¤ciency through increased photon capture for a given stimulus condition. We report an unusual surface grating on the compound eyes of an Eocene dolichopodid dipteran (45 Ma) known only from Baltic amber. By measuring the re£ective properties of a £at model of this grating constructed from material of appropriate refractive index we show that this`£y eye grating' is an e¤cient antire£ector of white light at angles up to 608, and a relatively good antire£ector for angles beyond 608. We calculate that such a grating would be particularly useful on a curved corneal surface as it would increase the transmission of incident light through the cornea compared with a smooth surface. This structure is also reported on the curved regions of the corneas of at least two extant dipterans. We argue that this grating probably derives from the previously described moth eye antire£ec-tion structure, which we also report here to occur in a silver¢sh, a`primitive' insect. The £y eye grating is a more e¤cient antire£ector than the moth eye structure only at angles greater than about 108 from the surface normal. A comparable antire£ector is employed on solar absorbers.

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