Naturwissenschaften (2005) 92: 444–450 DOI 10.1007/s00114-005-0017-6 ORIGINAL ARTICLE Jacobus C. Biesmeijer · Martin Giurfa · Dirk Koedam · Simon G. Potts · Daniel M. Joel · Amots Dafni Convergent evolution: floral guides, stingless bee nest entrances, and insectivorous pitchers Received: 1 January 2005 / Accepted: 27 June 2005 / Published online: 13 August 2005 C  Springer-Verlag 2005 Abstract Several recent hypotheses, including sensory drive and sensory exploitation, suggest that receiver biases may drive selection of biological signals in the context of sexual selection. Here we suggest that a similar mechanism may have led to convergence of patterns in flowers, sting- less bee nest entrances, and pitchers of insectivorous plants. A survey of these non-related visual stimuli shows that they share features such as stripes, dark centre, and peripheral dots. Next, we experimentally show that in stingless bees the close-up approach to a flower is guided by dark centre preference. Moreover, in the approach towards their nest entrance, they have a spontaneous preference for entrance patterns containing a dark centre and disrupted ornamen- tation. Together with existing empirical evidence on the honeybee’s and other insects’ orientation to flowers, this J. C. Biesmeijer () Centre for Biodiversity and Conservation, University of Leeds, Leeds, LS2 9JT, UK e-mail: j.c.biesmeijer@leeds.ac.uk J. C. Biesmeijer Neurobiology and Behavior, Cornell University, Ithaca, NY, USA M. Giurfa Centre de Recherches sur la Cognition Animale, CNRS–Universit´ e Paul Sabatier–Toulouse III, 31062 Toulouse Cedex 4, France D. Koedam Laboratorio de Abelhas, Universidade de S˜ ao Paulo, S˜ ao Paulo, Brazil S. G. Potts Centre for Agri-Environmental Research, Reading University, Reading, RG6 6AR, UK D. M. Joel Division of Weed Research, Agricultural Research Organization, Newe-Ya’ar Research Centre, Ramat Yishay 30095, Israel A. Dafni Institute of Evolution, Haifa University, Haifa 31905, Israel suggests that the signal receivers of the natural patterns we examined, mainly Hymenoptera, have spontaneous pref- erences for radiating stripes, dark centres, and peripheral dots. These receiver biases may have evolved in other be- havioural contexts in the ancestors of Hymenoptera, but our findings suggest that they have triggered the conver- gent evolution of visual stimuli in floral guides, stingless bee nest entrances, and insectivorous pitchers. Introduction To appreciate the design of biological signals we need to identify the signal receiver and understand its sensory phys- iology. This principle was advanced by Sprengel (1793) who argued that flowers present a suite of signals geared to the perceptual system of pollinators. Eighty years later Charles Darwin (1876) rediscovered Sprengel’s work and began to view pollination as an evolutionary process. At present, biological signals are characterised more ade- quately by analysing them from the perspectives of the receptor’s sensory physiology (reviewed by Endler 1992; Dafni and Giurfa 1999; Dafni et al. 1997a, b; Giurfa and Lehrer 2001; Menzel and Shmida 1993) and perceptual psychology (Guilford and Dawkins 1991, 1993; Dawkins and Guilford 1997; Chittka et al. 1999). This approach has been successfully applied using insects as a model system. In the particular case of insect pollinators, of which Hy- menoptera are the majority (Faegri and van der Pijl 1979; Proctor 1996), visual signals are of primary importance in location, identification, and recognition of food sources and the nest. Bees use floral colour and patterns to discriminate between flowers and to locate the nest upon return from the field (colour: von Frisch 1914; Daumer 1956, 1958, re- viewed by Menzel 1979; pattern: Hertz 1930; Wehner 1972; reviewed by Wehner 1981). Recently, some of the neuronal mechanisms associated with the processing of such visual signals have been identified (e.g., Backhaus 1991; Horridge 1994; Giurfa and Menzel 1997; Vorobyev et al. 1997). To- gether these findings provide a background that allows for the characterisation of natural patterns from flowers and