Egg Hornet
From Sonic Retro
The Egg Hornet is the first battle with Dr. Robotnik in Sonic Adventure. The Egg Hornet is a add-on to the Edd-O-Matic by equipping two large retractable drills at the side of the vehicle and three "Boosters" at the back. Dr. Robotnik uses the Egg Hornet to try and steal the Chaos emerald from Sonic and Tails. The Egg Hornet attacks by launching several small missiles at Sonic, then charges to the ground with the Drills trying to drill on top of Sonic.
Defeat Strategy
This boss is pretty simple, all you need to do is use your homing attack, aiming at the main body of the vehicle when Dr. Robotnik gets his drills stuck in the ground. Once you defeat the Egg Hornet then all add-ons break off from the main ship.