In order to level up and feed your scorpion you will need flies. Flies can either be found behind an area that can only be accessed by level 5 pets in the plains or either can be found on the island beside the desert with the dinosaurs. Flycatcher plants are the most viable way to feed scorpions
How to obtain
The scorpion can be obtained a total of 3 different ways. firstly you can buy the scorpion at the desert shop for 250 tickets. Secondly if you go to the plains and access the level 5 pet required room and complete scorpina's maze of DOOM you are rewarded with a scorpion egg. Thirdly you are able to capture them with any type of net.
The maze of DOOM
I hear you asking "how do I do this maze?" well thankfully I have the answer for you. First off you will want to go to the the plains region and go to the "Scorpion Temple".
After entering this structure you will be greeted by a door and a button, in order to proceed passed this you will need have a pet that level 5 or higher.
After entering the room you will see a scorpion directly in front of you, in front of iron bars.
Go talk to that scorpion and he should task you with completing his maze. Once you have reached the end of the "Maze of DOOM" you shall find a scorpion egg.
And finally I hope that you have found this informative and helpful for any questions you had before hand :)