Dang, that Hornet!
Hornet will be your first real test as she is quick and can cover distances fairly quick. If needed, pick up the Stalwart Shell from Sly, as this will give you more recovery time when hit. Approach this fight with the mindset of attacking and then escaping.
This is a pretty hard fight, so leaving it until you are stronger is not a bad decision. If you do decide to take the boss head on, now that it will probably take a few tries to beat. Basically this boss fight has two phases. The first phase you face off against a single Mantis Lord. The Mantis Lords are quick and teleport quickly around the arena.
Strategy wise, use your Dash to dodge and try to get damage in when possible. After dealing enough damage to the single Lord, you get to faceoff against two at once. This is where things get way more difficult. Note that the bosses moveset does not change; your simply facing two at once.
When you beat both, the fight is complete. Beating the Mantis Lords, de-aggros the Mantis in Mantis Village, meaning you can explore without risk of dying. You also get access to the Mantis treasure room.