Effects of macro- and micro-nutrients on momentary and season-long feeding responses by select species of ants

Few studies have investigated the relative contribution of specific nutrients to momentary and season-long foraging responses by ants. Using western carpenter ants, Camponotus modoc, and European fire ants, Myrmica rubra, as model species, we: (1) tested preferential consumption of various macro- and micro-nutrients; (2) compared consumption of preferred macro-nutrients; (3) investigated seasonal shifts (late May to mid-September) in nutrient preferences; and (4) tested whether nutrient preferences of C. modoc and M. rubra pertain to black garden ants, Lasius niger, and thatching ants, Formica aserva. In laboratory and field experiments, we measured nutrient consumption by weighing Eppendorf tubes containing aqueous nutrient solutions before and after feeding by ants. Laboratory colonies of C. modoc favored nitrogenous urea and essential amino acids (EAAs), whereas M. rubra colonies favored sucrose. Field colonies of C. modoc and M. rubra preferentially consumed EAAs and sucrose, respectively, with no sustained shift in preferred macro-nutrient over the course of the foraging season. The presence of a less preferred macro-nutrient in a nutrient blend did not diminish the blend’s ‘appeal’ to foraging ants. Sucrose and EAAs singly and in combination were equally consumed by L. niger, whereas F. aserva preferred EAAs. Baits containing both sucrose and EAAs were consistently consumed by the ants studied in this project and should be considered for pest ant control.

In each subpanel, different letters next to means indicate significantly different consumption levels in pairwise comparisons between means (see Table S2) d, n = 10) of aqueous solutions of (i) salts (0.25%, 0.5%, 1%; equal amounts of CuCl2, FeCl3, MnCl2, NaCl, ZnCl2, KH2PO4, MgSO4) and (ii) vitamins (0.25%, 0.5%, 1%; equal amounts of pamino benzoic acid, ascorbic acid, calcium pantothenate, folic acid, nicotinic acid, pyridoxin hydrochloride, riboflavin, thiamine, choline chloride).Grey symbols represent individual replicates and black symbols and whiskers denote estimated marginal means and 95% confidence intervals.Treatment (type of aqueous solution) was a significant predictor of consumption for salts and vitamins in M. rubra (see results).In each subpanel, different letters next to means indicate significantly different consumption levels in pairwise comparisons between means (see Table S3).0.39 (0.25-0.54) 0.25% V vs 0.5% V 0.32 0.99 0.25% V vs 1.0% V -3.33 0.005 0.5% V vs 1.0% V -3.62 0.002 Table S5: Modelled estimated marginal means (EMMs) and 95% confidence intervals (CIs) of proportional consumptions of aqueous solutions of urea, essential amino acids (EAA) or sucrose -presented singly and in ternary combination (Blend) -by colonies of Camponotus modoc and Myrmica rubra.The concentration of each macro-nutrient type was kept the same as in the ternary blend ('unadjusted') or matched the total nutrient concentration of the blend ('adjusted').

Supplementary Tables
We also report pairwise comparisons between treatments and their Tukey adjusted p-values. Exp

Table S1 :
Composition of nutrient test stimuli, their ratios, and purities for chemicals used in ant foraging experiments.

Table S2 :
Modelled estimated marginal means (EMMs) and 95% confidence intervals (CIs) of proportional consumption of aqueous solutions of sucrose (S) by colonies of Camponotus modoc and Myrmica rubra.We also report pairwise comparisons between treatments and their Tukey

Table S3 :
Modelled estimated marginal means (EMM) and 95% confidence intervals (CI) of proportional consumption of aqueous solutions of glycerides (G), fatty acids (FA), and sterols (S) by colonies of Camponotus modoc and Myrmica rubra.We also report pairwise comparisons between treatments and their Tukey adjusted p-values.

Table S4 :
Modelled estimated marginal means (EMMs) and 95% confidence intervals (CIs) of proportional consumptions of aqueous solutions of salts (S) and vitamins (V) by colonies of Camponotus modoc and Myrmica rubra.We also report pairwise comparisons between treatments and their Tukey adjusted p-values.

Table S6 :
Modelled estimated marginal means (EMMs) and 95% confidence intervals (CIs) of proportional consumptions of aqueous solutions of urea, essential amino acids (EAAs) or sucrose -presented in binary combinations and in a ternary blend (Blend) -by colonies of Camponotus modoc and Myrmica rubra.The concentrations and ratios of macro-nutrients in binary combinations were kept the same as in the ternary blend ('unadjusted'), or matched -at equivalent proportion -the total concentration of the ternary blend ('adjusted').We also report pairwise comparisons between treatments and their Tukey adjusted p-values.