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.

Keywords: Evarcha culicivora; Lantana camara; Parthenium hysterophorus; Ricinus communis; Salticidae; nectarivory.

Figure 1.

For Evarcha culicivora juveniles, percentages of individuals from different meal-type group that, after attacking, succeeded in capturing mosquitoes. Abbreviations for groups defined in table 1. N=200 for H₂O and 50 for each other group, (a) 3 day pre-trial fast. (b) 6 day pre-trial fast. Sequence of groups on x-axis for 3 day and for 6 day fast: from highest to lowest percentage after 3 day fast. Percentages lower for 6 day than for 3 day fasts, but rankings of groups by percentage comparable for 3 day and 6 day fasts.

Figure 2.

For Evarcha culicivora juveniles, predicted prey-capture success (i.e. probability of capture success after attacking mosquito) plus 95% confidence intervals after 3 day and 6 day fast. Predictions derived from logistic model (see text). Abbreviations for groups defined in table 1. (a) Spiders that fed on different plant species. (b) Spiders that fed on L. camara or on artificial L. camara nectar.

Figure 3.

For Evarcha culicivora juveniles, predicted prey-capture success (i.e. probability of capture success after attacking mosquito) plus 95% confidence intervals after 3 day and 6 day fast. Predictions derived from logistic model (see text). Abbreviations for groups defined in table 1. Spiders fed on different concentrations of (a) sucrose, (b) fructose, (c) glucose and (d) maltose.