Mosquitoes can harbor thousands of malaria-causing parasites in their bodies, yet while slurping blood from a victim, they transmit just a tiny fraction of them. In an effort to define precisely the location of the parasite bottleneck, scientists say they have discovered that the parasites are stopped by a roadblock along the escape route in the insect’s spit glands, a barrier that could potentially serve as a novel target for preventing or reducing malarial infection.