You will go away !

 This caterpillar of Swallowtail (Papilio machaon) was found on a roadside (Franche-Comté, August 2008). Its bold colours indicate a possible sick taste and are likely to worry animals that may attempt to eat it  When touched a little bit with a finger, the larva immediately retracts itself, bends the head and brings outside a weird organ called 'osmeterium'. This orange structure is typical within the Papilionidae family and acts as a repellant against predators. It releases a kind of stinky gas which is supposed to make the predator give up the attack.... the smell is not that strong for humans but is certainly more efficient against other animals and even perhaps parasitoïd insects
 As soon as the threat disappears, the caterpillar brings its osmeterium inside and does not even try to escape.