I'm not entirely sure of a specific story with exactly that title. But generally, in fables, lions are often seen as powerful, mosquitoes as annoying and small but pesky, and mice as meek. Maybe the mosquito could be a troublemaker for the lion king, and the mouse might play an unexpected role, like in the story of the lion and the mouse where the mouse helps the lion in the end.
In the story, the lion is caught in a hunter's net. The mouse, remembering the lion's kindness of sparing its life earlier, decides to help. It climbs onto the net and starts nibbling on the ropes. It keeps at it patiently until the ropes break and the lion is no longer trapped. This shows that the mouse's small size doesn't prevent it from being a great help to the large and powerful lion.
One possible moral could be that size doesn't matter. The mosquito, despite being tiny, can still cause trouble for the powerful lion king, and the mouse, though small, might have a role to play. Just like in life, small things or people can have a big impact.
The mouse uses its small but sharp teeth to gnaw at the net which has caught the lion. It's a simple act but very effective. Since the mouse is small and can move around easily, it can reach the parts of the net where the lion can't. This shows that size doesn't always matter when it comes to helping someone.
In the story, the lion is trapped in a hunter's net. The little mouse, which the lion had previously spared, hears the lion's roar of distress. It then scurries over to the net. With its tiny but sharp teeth, the mouse begins to nibble at the ropes of the net. It perseveres until the ropes are weakened enough for the lion to be able to break free. This demonstrates that the mouse, despite being small, has the ability and determination to save the much larger and stronger lion.