Dirge by Alan Dean Foster

In this science fiction narrative, a human survey team explores Argus V, a hospitable planet later renamed Treetrunk, only to encounter the Pitar, a beautiful and seemingly friendly alien species. While humanity is charmed by the Pitar’s physical similarity to themselves, the insectoid thranx remain cautious and observant of this new alliance. This trust is shattered when the Pitar launch a premeditated genocidal assault on the Treetrunk colony, systematically murdering hundreds of thousands of settlers. Alwyn Mallory, the sole survivor of the massacre, manages to record the atrocity, providing evidence of the Pitar's horrific obsession with harvesting human reproductive organs. This revelation sparks a retributive war, leading to a formal military partnership between humans and thranx. Together, they develop advanced stingship technology to bypass Pitarian defenses, solidifying the foundation of the Humanx Commonwealth.