bat-winged slugs
... that while mating, some species of bat-winged slugs stab each other with a two-pronged penis?
... that while mating, some species of <b id="mwBNI"><a href="./Gastropteridae" id="mwBNM" rel="mw:WikiLink" title="Gastropteridae">bat-winged slugs</a></b> <i id="mwBNQ">(pictured)</i> stab each other with a two-pronged penis?