From Zelda Wiki, the Zelda encyclopedia
The Deku Toad
excretes Toado eggs from its back
Toados are creatures that appear in the Lakebed Temple in Twilight Princess. These creatures hatch from eggs on the back of the Deku Toad during Link's battle with it. They hatch in large groups that simultaneously attack Link. Using the spin attack on these creatures will take them out quickly. It is also possible to kill most of them before they become a threat by shooting the back of the Deku Toad with Bomb Arrows.
It is believed that Toado, Toadpolis, and the Deku Toad are the same animal in different stages of its life cycle.