Wing development in parasitized male and female Sitobion fragariae

Different stages of presumptive winged morphs (males, gynoparae and alate virginoparae) of the blackberry-cereal aphid, Sitobion fragariae, were exposed to attack by Aphidius ervi. Even though the mechanism influencing wing development in the three aphid morphs differs, the effects of parasitism were similar. Alatiform structures were completely inhibited in all three morphs when the initial attack took place in their first or early second stadium. The disruption of wing development also resulted in apterous/alate-intermediate forms when aphids were attacked from first (males and gynoparae) or early second (alate virginoparae) up to the fourth larval stadium. The fact that wing development was still disrupted when aphids with well developed wingbuds were parasitized indicates that the early stages of parasitization were influential. Thus, the morphogenetic effects may be exerted by the parasitoid egg or calyx fluid.