PHEROMONES-98 - OLFACTORY ELECTROANTENNOGRAM RESPONSES OF THE FORMICINE ANTS LASIUS-NIGER AND FORMICA SPECIES (HYMENOPTERA, FORMICIDAE) TO 3,4-DIHYDROISOCOUMARINS

Electroantennogram (EAG) studies of the formicine genera Lasius and Fo rmica (Hymenoptera, Formicidae) were carried out with 3,4-dihydroisoco umarins, recently identified as trail pheromones within this ant subfa mily. The here investigated formicine species Lasius niger; Formica ru fa, F. fusca and F. sanguinea were all responsive towards stimuli of s ynthetic 3,4-dihydroisocoumarins. Synthesized samples of natural 3,4-d ihydroisocoumarins, found in the hindgut of these species evoke the hi ghest electrophysiological responses while structure analogues were le ss efficient. Number and position of the methyl groups of test substan ces were important factors for structure activity in EAG. F. fusca and L. niger showed a stereoisomeric differentiation in EAG responses bet ween (R)- and (S)-isomers of 8-hydroxy-3,5,7-trimethyldihydroisocoumar in, a component in the hindgut of both species. Higher electrophysiolo gical activity for )-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.