Rapid nectar-meal effects on a predator's capacity to kill mosquitoes

Abstract

Using Evarcha culicivora, an East African jumping spider (Salticidae), we investigate how nectar meals function in concert with predation specifically at the juvenile stage between emerging from the egg sac and the first encounter with prey. Using plants and using artificial nectar consisting of sugar alone or sugar plus amino acids, we show that the plant species (Lantana camara, Ricinus communis, Parthenium hysterophorus), the particular sugars in the artificial nectar (sucrose, fructose, glucose, maltose), the concentration of sugar (20%, 5%, 1%) and the duration of pre-feeding fasts (3 days, 6 days) influence the spider's prey-capture proficiency on the next day after the nectar meal. However, there were no significant effects of amino acids. Our findings suggest that benefits from nectar feeding are derived primarily from access to particular sugars, with fructose and sucrose being the most beneficial, glucose being intermediate and maltose being no better than a water-only control.

Wandering and web spiders feeding on the nectar from extrafloral nectaries in neotropical savanna

“…culicivora in the period between emerging from the egg sac and the first encounter with prey was later confirmed by Carvell et al . (). Additional studies are necessary to determine the significance of nectar feeding for spiders along their development.…”

“…They concluded by means of choice tests done with spiders that sugar, and not just water, is relevant to salticids because these spiders spent more time drinking from a simulated nectar source (30% sucrose solution) than from distilled water during the experiment. In addition, Carvell, Kuja & Jackson () showed that consumption of sugar (sucrose, fructose, glucose and maltose) by Evarcha culicivora (Salticidae) juveniles in artificial diets influence positively spider's prey‐capture proficiency on the next day after the nectar meal. However, probably water is also important in Cerrado, since it is a relatively hot and dry environment, and spiders are sensible to desiccation (Pulz, ).…”

Ontogenetic shift in plant-related cognitive specialization by a mosquito-eating predator

“…In laboratory olfactometer experiments (Cross and Jackson, 2009b), adult females, adult males and juveniles from all size classes were attracted to the odour of two plant species, L. camara and R. communis . The juveniles of E. culicivora are especially inclined to feed on nectar when they visit plants (Kuja et al, 2012) and there is a specialized relationship between nectar meals and predation on mosquitoes: after nectar meals, the juveniles of E. culicivora become more effective at subduing the mosquitoes they attack (Carvell and Jackson, 2015). However, we propose that mating instead of feeding is the context in which E. culicivora adults make specialized use of plants.…”

“…‘Plant specialist’ is another convenient expression when discussing E. culicivora but progress at understanding what plants, especially L. camara and R. communis , mean to this spider has been slow in comparison to advances in our understanding of specialization on mosquitoes. Earlier research suggests that visiting plants has different functions depending on whether the spider is an adult or a juvenile, with juveniles using plants primarily as food sources (Kuja et al, 2011; Carvell et al, 2015) and adults using plants as mating sites (Cross et al, 2008). However, our experiments here were designed to examine what plants mean to E. culicivora from a different perspective.…”

“…Adults, but not juveniles, are also attracted to cineole, albeit less strongly than to caryophyllene and humulene. Another juvenile-adult difference is that, after a fast, the juveniles but not the adults of E. culicivora become more strongly attracted to the odour of caryophyllene and humulene (Nelson and Jackson, 2013; Kuja et al, 2012), with the benefits of nectar meals for juveniles including rapid improvement in their prey-capture efficiency (Carvell et al, 2015). Although the role of plants in the biology of adults is less well understood, natural-history observations suggest that L. camara might be important as a mating site (Cross et al, 2008).…”