Phytochemical arrestants for the leaf-cutting ants,Atta cephalotes(L.) andAcromyrmex octospinosus(Reich), with some notes on the ants' response

Abstract

Albedo (the inner, white part of the rind) of the grapefruit (Citrus parodisi) and the flowers of the garden hibiscus (Hibiscus rosa-sinensis) were analysed for the presence of chemo-stimulants for the leaf-cutting antsAtta cephalotes(L.) andAcromyrmex octospinosus(Reich). Two distinct types of chemical substances in grapefruit albedo (unabsorbed sapids from a cation-exchange resin I.R. 120, and the total lipid fraction) were significant arrestants forAtta cephalotes, whilst five types of chemical substances (absorbate on the cation-exchange resin I.R. 120, unabsorbed sapids from the same resin, the total lipid fraction, absorbate on a polyamide resin, and neohesperidosides) arrestedAcromyrmex octospinosus. For both ant species, the unabsorbed sapids from the polyamide resin appeared to be the most attractive of the relatively refined fractions. A preliminary analysis showed a similar situation for hibiscus flowers.Both ant species preferred young to older grapefruit leaves. There appears to be a chemical basis for this, and in the case ofA. octospinosusthere was evidence of the existence of repellents in the older leaves and in grapefruit flavedo (the outer, yellow part of the rind).Substantial heterogeneity in preferences was detected in a given nest from day to day, between different nests of the same species, and between the two species. It is suggested that this is attributable to social phenomena evolved by the ants.