Pheromones 98* Olfactory Electroantennogram Responses of the Formicine Ants Lasius niger and Formica Species (Hymenoptera: Formicidae) to 3,4-Dihydroisocoumarins

Abstract

Electroantennogram (EAG) studies of the formicine genera Lasius and Formica (Hymenoptera, Formicidae) were carried out with 3,4-dihydroisocoumarins, recently identified as trail pheromones within this ant subfamily. The here investigated formicine species Lasius niger, Formica rufa, F. fusca and F. sanguinea were all responsive towards stimuli of synthetic 3,4-dihydroisocoumarins. Synthesized samples of natural 3,4-dihydroisocoumarins, found in the hindgut of these species evoke the highest electrophysiological responses while structure analogues were less efficient. Number and position of the methyl groups of test substances were important factors for structure activity in EAG. F. fusca and L. niger showed a stereoisomeric differentiation in EAG responses between (R)- and (S)-isomers of 8-hydroxy-3,5,7- trimethyldihydroisocoumarin, a component in the hindgut of both species. Higher electrophysiological activity for (R)-8-hydroxy-3,5,7-trimethyl-3,4-dihydroisocoumarin in comparison to the (S)-isomer agrees with better behavior responses of previous trail following tests in the case of Lasius niger.