You can see how this posture got its name; it looks just like a scorpion. There are two versions of Vrischikasana. The first one is done from Forearm Balance, or Pinca Mayurasana. This is an easier version of Scorpion to balance in, but it also requires more stretch in the shoulders. The second version is done from Handstand. It is useful to play with both of them.
Prerequisites: You need strength, shoulder flexibility and a deep back bend to do Scorpion.
Strength: There are two separate areas of strength necessary for Vrischikasana: One is core and the other is shoulders. You can build strength in both of these areas at the same time by practicing your ability to hold the various plank positions. There are four versions of Plank Pose on your hands: forward, to the right side, to the left side and Reverse Plank. In the beginning, try holding each one for 20 seconds. Build up to being able to hold each one for a minute. You can also try holding Plank Pose on your forearms.
Shoulder flexibility: To do Scorpion and keep your shoulders and your rotator cuff safe, you need to work on stretching your arms overhead. You should be able to stretch your arms overhead and have them be in a straight line with your body without arching your back. If you cannot do this, it is important to work on stretching your shoulders by doing poses like Warrior III with your hands on a ledge, or in Down Dog.
Back bends: As you can see in my Scorpion, I cannot get my feet to my head, yet. So, it is not necessary to be able to do so to work on the pose, but you should be pretty strong in your Wheel. Try practicing Wheel against the wall. Start by placing your wrist creases at the corner of the wall and the floor. When you lift up into Wheel, move your chest in the direction of the wall. If your chest can touch the wall, you can begin to work on coming down on your forearms in Wheel. Press your elbows against the wall and begin to move your chest toward the wall. Camel is another great pose that will help with your Scorpion. More than Wheel, Camel will also work to strengthen your abs. From Camel, you can progress to what is often called Pigeon Droppings. This is where you drop back from Camel to your hands.
Arm balances: No matter which of the two Scorpion versions you try, you should be pretty comfortable in Forearm Balance and in Handstand. This doesn’t mean that you have to be able to balance in these poses in the middle of the room, but you should be relatively strong in each one of these at the wall.
Remember not to rush the pose. Take your time and enjoy the process. Set small, achievable goals for yourself and celebrate each time you reach one. You don’t want to get stung by forcing yourself into Scorpion!