Yet another secret
: You can become the spider
. Just click the button as if you were going to change your ant, and instead click on the spider's mandibles (the mouth bit).
Wah-ha! Now you can use your new mighty form to devour your enemies whole, or turn traitor and attack your own colony, rampaging with an orgy of psychological terror and--er, ahem. Just don't go off the screen or let the ants swarm you, or you'll die.
Then again, sacrificing yourself for the colony as food is somewhat noble...