Ultraviolet cues affect the foraging behaviour of jumping spiders DAIQIN LI & MATTHEW L. M. LIM Department of Biological Sciences, National University of Singapore (Received 25 August 2004; initial acceptance 15 October 2004; final acceptance 31 December 2004; published online 18 August 2005; MS. number: 8255R) Jumping spiders have long been known to have large principal eyes with ultraviolet (UV) receptors, and many species of their arthropod prey have body parts that reflect strongly in the UV waveband. However, no attempt has been made to investigate the effects of UV cues from prey on the foraging behaviour of jumping spiders. We performed laboratory experiments to test the hypothesis that jumping spiders use UV cues for locating and discriminating prey. We used Portia labiata, a web-invading, spider-eating jumping spider, as the predator and Argiope versicolor, an orb-web-building spider that decorates its web with UV- reflecting silk stabilimenta, as prey. Portia labiata could detect the difference between UV-reflecting and non-UV-reflecting stabilimentum-decorated webs and they preferentially approached the UV-reflecting ones. These findings may have wide implications for studies of animal foraging, and support one hypothesized function of salticid UV vision, the role of which is largely unknown. Ó 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. A wide range of animals from crabs to birds can see into the ultraviolet (UV) part of the spectrum (300–400 nm; Jacobs 1992; Tove ´e 1995), to which humans are blind. Furthermore, they may also view the visible wavebands (400–800 nm) in a different way to us (Cuthill et al. 2000a, b). Until recently, the functional significance of UV vision has largely been ignored (reviewed in Jacobs 1992; Bennett & Cuthill 1994; Bennett et al. 1994; Cuthill et al. 2000a, b). Animals may use UV for many things, including signalling, foraging, social signalling, orienta- tion and navigation (e.g. Jacobs 1992; Bennett & Cuthill 1994; Tove ´e 1995; Cuthill et al. 2000a, b). The role of UV in sexual signalling and in mate choice in particular has been most extensively studied in vertebrates, particularly in birds (Bennett et al. 1996, 1997; Andersson & Amund- sen 1997; Hunt et al. 1997, 1998, 1999; Andersson et al. 1998; Johnsen et al. 1998; Pearn et al. 2001; Siitari et al. 2002a; Alonso-Alvarez et al. 2004). Animals may also use UV cues from food items when foraging. There is a great deal of UV light in nature (Endler 1993) and many food items either absorb, scatter or reflect strongly in the UV region of the spectrum. Furthermore, many leaves, bark and soil (i.e. natural backgrounds) do not reflect UV (Endler 1993), increasing the contrast between the food item and its background. Thus, UV cues may enhance the detection or discrimination of prey (Tove ´e 1995). Many flowers also reflect in the UV, and pollinating insects and birds use UV cues from flowers when foraging (Goldsmith 1980; Menzel & Shmida 1993; Chittka et al. 1994). Many terrestrial arthropods such as insects and spiders, which are potential prey for many species of predatory arthropods, reptiles and birds, also reflect UV light (Vane-Wright & Boppre 1993; Oxford & Gillespie 1998). An area of behavioural ecology in which UV-sensitivity may be important is in predator–prey interactions. How- ever, little attention has been paid to the role of UV in foraging for prey (Viitala et al. 1995; Church et al. 1998a; Siitari et al. 1999, 2002b; Honkavaara et al. 2002). Furthermore, the potential function of UV signals in invertebrates is still poorly understood, although UV vision was first demonstrated in insects (Silberglied 1979). In this study, we investigated the importance of UV cues in the foraging of an invertebrate predator. We used a web-invading, spider-eating jumping spider Portia labiata (Thorell) (Araneae: Salticidae) as the predator and a species of orb-web-weaving spider Argiope versicolor (Doleschall) (Araneae: Araneidae) as prey. This is an ideal system to test the importance of UV cues in a predator’s foraging for several reasons. First, P. labiata is sympatric with, and a natural predator of, A. versicolor (Seah & Li 2001). Second, Portia spp. possess remarkably acute vision (Blest et al. 1990) that permits them to discriminate visually between different objects, such as prey, predators, conspecifics and webs (Jackson & Blest 1982; Li & Jackson 1996). Third, jumping spiders have UV-sensitive cells in their principal (anterior median) eyes Correspondence: D. Li, Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, 117543, Singapore (email: dbslidq@nus.edu.sg). 771 0003–3472/04/$30.00/0 Ó 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. ANIMAL BEHAVIOUR, 2005, 70, 771–776 doi:10.1016/j.anbehav.2004.12.021