python, boa constrictor
蠎 centers on large constricting snakes: pythons and boa constrictors. The two meanings are closely related as heavy-bodied non-venomous snakes that squeeze prey.
蠎 combines the insect/creature radical 虫 with 莾, which likely contributes the sound. The character is used for large snakes, but the exact historical development of the right component is uncertain.
The left side 虫 signals a creeping creature, and the right side 莾 looks like a thick, tangled shape. Picture a massive python coiled in dense undergrowth: 蠎 is that python.
For ボウ, imagine a python squeezing its prey with a low, booming sound: bow -> ボウ, like the deep vibration of a constricting snake.