Development of aedeagus after Snodgrass, from two phallic lobes (A) to four phallomeres (C), the outer ones becoming parameres (green), the inner ones growing together and forming distal aedeagus (F, red)
<a href="//commons.wikimedia.org/wiki/User:Siga" title="User:Siga">Siga</a>
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<span class="int-own-work" lang="en">Own work</span>