This was awesome. First off, really cool game page. I loved how well it matched the title screen and the overall style of the game.
The art is really unique and fits the concept so well. The background art for each bug complemented them nicely, and I loved all the boss title names too. The music you created was awesome, but the bee theme especially stood out. I actually hesitated to kill it at one point because I wanted to keep hearing it XD.
The little excerpt and art before the fly was hilarious too. Gameplay-wise, this was really fun. The controls felt responsive, which was important since the whole game is built around melee/swatting. The bullets were easy to see, and the attack patterns were good.
The final fly boss was done really well. I liked how its arsenal felt like a mix of the previous patterns all thrown at you at once. It was very challenging, and it kind of reminded me of Sans from Undertale, dodging everything until it finally gets tired and then wham, dead.