willow sawflies
... that in the Southern Hemisphere, all willow sawflies are female, while in the Northern Hemisphere both males and females occur?
... that in the Southern Hemisphere, all <b id="mwAXw"><a href="./Nematus_oligospilus" id="mwAX0" rel="mw:WikiLink" title="Nematus oligospilus">willow sawflies</a></b> are female, while in the Northern Hemisphere both males and females occur?