Monika HILKER-1, Stefan SCHULZ-2, Jurgen GROSS-1
1-Freie Universität Berlin, Institut für Zoologie,
Haderslebenerstr. 9, D-12163 Berlin, Germany;
2-Universität Hamburg, Institut für Organische Chemie.
Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
Chrysomela lapponica is known to form distinct populations feeding upon willow or birch. A Czech and a Finnish population of Chrysomela lapponicawere compared with respect to (1) feeding preferences of larvae and adults, (2) antipredatory compounds of the eggs, (3) composition of the defensive larval secretions, and (4) morphological differences (size, colour) of adults. In the field, individuals of the Czech population were found feeding upon Betula pubescens, whereas the Finnish specimens were found mainly upon Salix borealis. Laboratory experiments revealed that the Finnish individuals do not feed upon birch (Betula pendula, B. pubescens)when offered in choice (birch - willow) or non-choice tests. Both larvae and adults of the Czech population clearly preferred birch to willow. The feeding preferences are modulated by the presence or absence of salicin. Feeding of individuals of the Czech population was deterred by salicin, whereas feeding of the Finnish individuals was stimulated by this phenolglycoside. Females of the Finnish population incorporate salicin into their eggs. The defensive exocrine secretions of larvae of the Czech population contain isobutyric acid, 2-methylbutyric acid and esters of the two, whereas the Finnish larvae emit salicylaldehyde as major component by their glandular secretion and carboxylic acid esters just as minor constituents. The differences in size between Finnish and Czech adults are small, but their different coloration is striking. The adaptive values of these differences will be discussed.
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