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.