From my camel I noticed that the whole mass of the grass seemed violently agitated, although there was no wind. On dismounting I found that the motion was caused by the contortions of pupae of V. cardui, which were so numerous that almost every blade of grass seemed to bear one. [...] the pupae began to burst and the red fluid that escaped sprinkled the ground like a rain of blood. [...] the whole swarm rose as a dense cloud and flew away eastwards towards the sea. 
                                                                                                                                                                                                 (Skertchly: Nubia, Sudan 1869)

Watch the divulgation video on the amazing migration of the butterfly V. cardui from Europe to the tropical savannah!

Vanessa's Odyssey, tribute to the butterfly Vanessa cardui and her incredible journey