Mothron

Mothron is a resilient flying enemy that spawns during the Solar Eclipse event and passes through blocks. It can only spawn after all Mechanical Bosses have been defeated. Mothron attacks by lunging at the player. Occasionally it lands on blocks to lay several Mothron Eggs that will spawn Baby Mothrons if they are not destroyed in time, much like Lepus.

Tips
To kill it without any danger, you have to have good wings, chlorophyte-made armor and movement equipment. Then, fly in the left and in the right, and stop to fly when you begin to fall. The Mothron will follow you, but you are normally faster. You can easily shoot it, with a straight weapon like Megashark, Unholy Trident or any Broken hero sword made weapon.

Or, for an even easier time, use the Piranha Gun. The Piranha projectile damages anything it comes in contact with while still latched to the target, so it will destroy any eggs Mothron lays. Additionally, it will slow Mothron making it easier to dodge its attacks. It will take about 20-25 seconds to of sustained Piranha to kill Mothron, or 40-50 seconds on Expert mode. This can be further accelerated by wearing ranged damage boosting armor such as the appropriate Hallowed Armor set.

Another solution requires a minecart rail system, preferably in the sky, which you mount as soon as a Mothron appears, and quickly accelerate to max speed. This works best with a Mechanical Cart, allowing you to match Mothron's normal movement speed by staying near the max speed. Once you have achieved this, you can keep a Yoyo right on top of the Mothron, or just use any ranged weapon to deplete its health. If you try to melee while doing this, though, sometimes Mothron will activate its lunge attacks, so that defeats the primary purpose of this method, though melee projectiles do not cause this behavior due to their ability to strike from a distance.

Trivia

 * Mothron is a reference to Mothra from the namesake 1961 movie. The subtle change in its name follows the trend of Terraria enemies' and bosses' names ending with the suffix -ron, such as Skeletron, Duke Fishron, and Pigron.
 * If the Eclipse finishes, or all players die, Mothron floats up to the sky and despawns, similar to the Eye of Cthulhu. In addition, it becomes invincible after the end of the Eclipse.

History
Mothron