How would you like to be a member of Instagram's new alpha program for Android users?
This information comes from a verified Instagram employee who was trying to scrounge up some Android subscribers for the app's alpha program on reddit's r/Android subreddit. Since the post has disappeared, we can only conclude that the site met its quota and now has enough alpha members for its Android app. However, you can still use Google Groups to join the alpha if you so desire.
So if you're interested in becoming an alpha tester for the Android version of Instagram, click on the two sourcelinks below. One will take you to Google Groups where you will verify some information. The second link takes you to Google Play where you will be sent the necessary links to become a tester.
source: GoogleGroups, Instagram via AndroidPolice