Evolution of gustatory sensitivity in Yponomeuta caterpillars: sensitivityto the stereo-isomers dulcitol and sorbitol is localised in a single sensory cell

The cellular localisation of the sensitivity to two host-plant specific lar val phagostimulants was determined in Yponomeuta evonymellus and in inter-s pecific hybrids of Y, cagnagellus and Y. padellus. The combined results of cross-adaptation experiments, analysis of mixture responses and inter-spike interval distributions indicated that the sensitivity for sorbitol and dul citol is localised in the same cell in the investigated species. This resul t suggests that during the evolution of the genus the main alteration in th e mechanism of sugar-alcohol detection occurred at the level of the recepto r proteins, Relatively simple modification of this kind can, however, have large effects, since larvae with modified receptor proteins will directly r espond to the new stimulus while all central processing and resulting behav iour can remain unmodified.