FORAGING BEHAVIOR AND ENCAPSULATION ABILITY OF DROSOPHILA-MELANOGASTER LARVAE - CORRELATED POLYMORPHISMS - (DIPTERA, DROSOPHILIDAE)

Larvae of Drosophila melanogaster are polymorphic with respect to thei r foraging behavior. ''Rovers'' move around, while ''sitters'' stay mo re in one place. This difference in movements while foraging may resul t in differences in the rate at which these larvae are attacked by hym enopteran parasitoids, especially by those that locate their hosts by reacting to the vibrations they make. From previous work it is known t hat D. melanogaster larvae show intra- and inter-population variation in their ability to destroy parasitoid eggs by encapsulation. If rever s have a higher probability to be attacked by a parasitoid, they may h ave a higher developed encapsulation system as compensation for this h igher attack probability. Experiments show that revers are indeed more often attacked by Asobara tabida, a vibrotactic (=reacting to vibrati ons) parasitoid, than sitters. However, foraging behavior and encapsul ation ability appear to be independent of each other in D. melanogaste r. This shows that the large variation between populations in encapsul ation ability is not a reflection of the relative proportion of revers and sitters in the populations. It also shows that parasitoids can be an important factor in the maintenance of the foraging behavior polym orphism, because a higher encapsulation ability is not a compensation for a higher attack probability.