SHORT COMMUNICATION Nectar feeding increases exploratory behaviour in the aphid parasitoid Diaeretiella rapae (McIntosh) Y.-D. Varennes 1 , M. Gonzalez Chang 1 , S. Boyer 1,2 & S. D. Wratten 1 1 Bio-Protection Research Centre, Lincoln University, Lincoln, Canterbury, New Zealand 2 Unitec Institute of Technology, Auckland, New Zealand Keywords Biological control, Brevicoryne brassicae, Fagopyrum esculentum, floral subsidies, Myzus persicae Correspondence Yann-David Varennes (corresponding author), Bio-Protection Research Centre, PO Box 85084, Lincoln University 7647, Lincoln, Canterbury, New Zealand. E-mail: yann-david. varennes@lincolnuni.ac.nz Received: July 28, 2015; accepted: September 30, 2015. doi: 10.1111/jen.12281 Abstract Feeding on floral nectar has multiple positive effects on parasitic wasps, including increased longevity and fecundity, and in addition, nectar feed- ing can also alter parasitoid behaviour. To advance understanding of the effects of nectar feeding on Diaeretiella rapae (McIntosh) [Hymenoptera: Braconidae], the activities of 1-day-old female D. rapae with or without a prior buckwheat (Fagopyrum esculentum) nectar meal were quantified. Nectar increased searching time of D. rapae by a factor of 40 compared with individuals provided with water only and reduced the time spent sta- tionary. The number of attacks to aphids by nectar-fed parasitoids was not significantly (P = 0.06) higher than that of unfed D. rapae, suggesting that the conditions of the experiment facilitated host finding by ‘quiet’ para- sitoids. Nevertheless, nectar feeding modified the behaviour of D. rapae in a way that parasitoids were more explorative and less inactive. This repre- sents one additional mechanism through which nectar feeding impacts parasitoid biology and suggests that a synergy between increased host searching, increased longevity and increased fecundity should lead to an enhancement of biocontrol when D. rapae females have access to nectar in the field. Introduction In their adult stage, parasitoid wasps feed on carbohy- drate-rich liquids, for example floral nectar or honey- dew (Jervis et al. 1993; Jervis 1998). This feeding strongly increases parasitoid longevity, and in the case of synovigenic parasitoids (i.e. able to mature eggs during their adult stage), it also increases egg matura- tion rate (Berndt and Wratten 2005; Vattala et al. 2006; Winkler et al. 2006; Lee and Heimpel 2008; Araj et al. 2009). In the field, the addition of flower- ing vegetation nearby or within crops generally, but not always, enhances pest parasitism rate (Tylianakis et al. 2004; Heimpel and Jervis 2005; Lavandero et al. 2006; Jonsson et al. 2008; Gurr et al. 2012; W€ ackers and van Rijn 2012; Balmer et al. 2014). In addition to increasing longevity and fecundity, nectar feeding can also affect other biological functions of parasitoids, such as host searching, host perception and flying abilities. For example, the aphid parasitoid Aphidius ervi (Haliday) [Hymenoptera: Braconidae] allocated more time to walking (exploratory behaviour) and attacking hosts when it had fed on nectar than when starved, in which case it remained stationary for most of the time (Araj et al. 2011). Other studies have used diluted honey solutions instead of nectar and have shown that the parasitoids Microplitis croceipes (Cres- son) [Hymenoptera: Braconidae] and Cotesia rubecula Marshall [Hymenoptera: Braconidae] had longer fly- ing bouts when fed than when starved (Takasu and Lewis 1995; Siekmann et al. 2004). However, fed and unfed C. rubecula allocated equal times to walking and being stationary, suggesting that feeding did not increase exploration by walking and did not reduce times of apparent inactivity (Siekmann et al. 2004). Such contrasting results suggest that there may be specific differences in nectar metabolism and beha- vioural responses to feeding. © 2015 Blackwell Verlag GmbH 1 J. Appl. Entomol.