Odor-based recognition of nectar in cursorial spiders

Carnivorous arthropods are known to rely on non‐prey foods, such as honeydew, pollen, and nectar. Consumption of plant‐based nutrients by spiders also appears to be widespread, especially in cursorial species. This is not surprising, as studies have shown that these spiders’ activity levels, survivorship, and reproduction are increased when their diet includes plant‐based nutrients, especially under conditions of prey scarcity. However, the sensory and behavioral means by which they recognize and locate non‐prey food is unknown. Here we show that immatures of a nectarivorous spider Hibana futilis Banks (Araneae: Anyphaenidae)] can recognize and remember particular chemical stimuli associated with nectar. Following ingestion of minute amounts of sugar, these spiders exhibited counterturning and other local searching behaviors that increased their chances of finding more nectar. When placed on test arenas, spiders that were naïve with respect to nectar aroma located artificial nectaries composed of diluted honey significantly faster than unscented nectaries composed of 1 m sucrose solution. These results indicate that H. futilis is neurophysiologically and behaviorally adapted for recognizing olfactory stimuli. Interestingly, only spiders that ingested sugar and were engaged in local search responded to nectar aroma, suggesting that stimulation into local search is necessary to prime olfactory responses. We found that H. futilis could be conditioned to associate the presence of nectar with a novel aroma, in this case vanilla, and remember this aroma over the course of several hours. In arenas with vanilla‐scented nectaries, spiders that had previous experience feeding on vanilla‐scented sucrose droplets located the nectaries significantly faster than did vanilla‐naïve spiders. The capacity to remember specific aromas could enhance the spiders’ ability to find nectar, either when moving between different parts of the same plant or among different plant species. The results here indicate that nectarivorous spiders possess the sensory capabilities and programed behaviors necessary for efficient detection, recognition, and location of nectar sources.