““For one group of wasps, the braconids, transferred genes have enabled a bizarre form of pest control. The females of these wasps lay their eggs in still-living caterpillars, which their young then devour alive. To give the grubs a hand, the females also inject the caterpillars with viruses, which suppress their immune systems. These are called bracoviruses, and they arent' just allies of the wasps: they are part of the wasps. Their genes have become completely integrated into the braconid genome, and are under its control. When a female wasp builds her viruses, she loads them with the genes they need to attack a caterpillar, while withholding those they need to reproduce or spread to different hosts. The bracoviruses are domesticated viruses! They're entirely dependent on the wasps for their reproduction. Some might say that they are not viruses at all; they're almost like secretions of the wasp's body rather than entities in their own right. They must have descended from an ancient virus, whose genes wheedled their way into the DNA of an ancestral braconid and stayed there. This merger gave rise to over 20,000 species of braconid wasps, all of which have bracoviruses in their genomes-an immense dynasty of parasites that uses symbiotic viruses as biological weapons.””
