Figure 3.

Hmong refugees from Laos, who collaborated with the American armed forces during the Vietnam War, accused the Soviet Union of attacking them with biological or chemical weapons. However, the alleged toxin warfare agent known as yellow rain matches perfectly the yellow spots of bee faeces on leaves in the forest of the Khao Yai National Park in Thailand. (Image reprinted with permission from Seeley et al., 1985 © (1985) M. Meselson, Harvard University).