If natural selection on fluctuating asymmetry (FA) is common and relat
ed to trait functionality, then vestigial traits should show elevated
FA. Moreover, if FA increases with heterozygosity, then haploid males
of haplodiploid taxa should exhibit higher FA than diploid females. We
measured fluctuating asymmetry of functional traits (fore femora of s
oldier morphs and disperser morphs, and wings of dispersers) and a ves
tigial trait (wings of soldiers) in the eusocial haplodiploid gall thr
ips Oncothrips tepperi (Insecta: Thysanoptera). Wing FA, but not femur
FA, was substantially and significantly higher in soldiers than in di
spersers in both sexes. Patterns of intersexual variation in FA were c
omplex: for wings, female soldiers had higher FA than male soldiers bu
t male dispersers had higher FA than female dispersers, and for femora
, males and females did not differ in FA in either morph. Our results
suggest that vestigial traits exhibit higher FA because of relaxation
of selection for functionality, and that haploidy does not necessarily
lead to increased FA in males of haplodiploid taxa.