Fatty acids and glycerides are object recognition and carrying cues for foraging Camponotus modoc carpenter ants

Abstract

During foraging and nest hygiene maintenance (removal of deceased nestmates), ants recognize objects for pickup and transport based on their surface chemicals. Diverse lipids are present on food items and deceased nestmates of ants and the lipids oleic acid and 1,2-diolein are already well-known pickup cues. However, the effects of various lipid types on pickup behaviour by ants have not yet been rigorously compared. Using the carpenter ant, Camponotus modoc Wheeler (Hymenoptera: Formicidae), as a model species and pieces of perlite as inert objects for pickup by ants, we (1) compared the effects of fatty acids and glycerides as perlite coating on perlite pickup and transport by ants, (2) tested the effect of 1,2-diolein dose on perlite pickup and (3) compared pickup behaviour by ants in response to pickup cues that are widespread (oleic acid and 1,2-diolein) and commercially used in ant baits (soybean oil). Of 18 surface chemicals tested singly as perlite coating, 1,2-diolein, linoleic acid, oleic acid, trilinolenin and triolein elicited the strongest perlite pickup behaviour. Increasing doses of 1,2-diolein correspondingly enhanced perlite pickup by ants. Oleic acid and 1,2-diolein as perlite coating prompted more perlite pickup by ants than soybean oil. Enriching soybean oil with oleic acid might enhance the pickup efficacy of granular baits by pest ants.