Outside Tapachula, Chiapas, Mexico—10 miles from Guatemala. To reach the cages, we follow the main highway out of town, driving past soy, cocoa, banana and lustrous dark-green mango plantations thriving in the rich volcanic soil. Past the tiny village of Rio Florido the road degenerates into an undulating dirt tract. We bump along on waves of baked mud until we reach a security checkpoint, guard at the ready. A sign posted on the barbed wire–enclosed compound pictures a mosquito flanked by a man and woman: Estos mosquitos genéticamente modificados requieren un manejo especial, it reads. We play by the rules.