a new genus
... that an entomologist cried "Aha!" when he discovered a new genus of Australian wasp, and that became its name?
... that an entomologist cried "<a href="./Eureka_effect" id="mwvg" rel="mw:WikiLink" title="Eureka effect">Aha</a>!" when he discovered <b id="mwvw"><a href="./Aha_(wasp)" id="mwwA" rel="mw:WikiLink" title="Aha (wasp)">a new genus</a></b> of Australian wasp, and that became its name?