Sensory matched filters Eric J. Warrant  Current Biology  Volume 26, Issue 20, Pages R976-R980 (October 2016) DOI: 10.1016/j.cub.2016.05.042 Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 Matched filtering as both benefit and liability. (A) An unknown species of male mayfly showing the enormous “turbanate” dorsal superposition compound eyes used solely for the detection of females, and the smaller ventral apposition compound eyes. The two small bulbous eyes below the dorsal eyes are the ocelli. Photo credit: Laurie Knight (www.laurieknight.net). (B) The rare Madagascan spider Exechocentrus lancearius, a bolas spider that exudes a single silk strand with not one but two sticky globules. Photo courtesy Gustavo Hormiga, George Washington University, USA. (C) A female firefly (Photuris versicolor) consumes a male firefly (in this case Photinus tanytoxus) that she lured by mimicking the light flash pattern of a P. tanytoxus female. Photo courtesy James E. Lloyd, University of Florida, USA. Current Biology 2016 26, R976-R980DOI: (10.1016/j.cub.2016.05.042) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 The ‘love spots’ of flies. (A,B) Male (A) and female (B) blowfly heads (Calliphora erythrocephala). Note how the eyes of males almost touch, whereas those of females are quite separated. The extra eye surface — or ‘love spot’ — of males (dotted white line) provides the input to a sophisticated neural pathway for detecting and chasing females. Images from Strausfeld 1991, with kind permission from Springer Science+Business Media. (C,D) In the hoverfly Volucella pellucens the male love spot is a large dorsal-frontal acute zone, where interommatidial angles are small (C) and facet diameters are large. The visual fields of the left eyes of the two sexes, and interommatidial angles shown by isolines, are projected onto spheres. The females have a much smaller frontal acute zone (compare the shaded regions, where Δϕ < 1.1°). D dorsal, V ventral, A anterior, L lateral. Republished with permission of Princeton University Press from Cronin et al. 2014. (E,F) Neural images (from the frontal-dorsal eye region) in male (E) and female (F) houseflies reconstructed from photoreceptor responses to a dark 3.44° wide target moving at 180 degrees per second. The neural images show the instantaneous voltage responses of individual photoreceptors separated at angles appropriate for males (Δϕ = 1.6°) and females (Δϕ = 2.5°). The wider ‘love spot’ facets of males, and their superior ‘love spot’ photoreceptor performance, allow males to detect small moving targets with much greater spatial, temporal and voltage contrast. Crosses indicate the current position of the target. From Burton and Laughlin, 2003, reproduced with kind permission of the Company of Biologists. Current Biology 2016 26, R976-R980DOI: (10.1016/j.cub.2016.05.042) Copyright © 2016 Elsevier Ltd Terms and Conditions