Parasites are an enemy in The Consuming Shadow. They are one of the new enemy variants that appear in the Insanity Edition.
Parasites are Worker Buzzers that randomly appear from a fallen enemy. You can tell if they are within the enemy by listening for the Buzzer's characteristic buzzing sound effect. If you don't see a buzzer around, its inside the enemy that's approaching you. Summoners tend to be their hosts.
Other than that, they are just as frail as regular Worker Buzzers.
In-game description Edit
Minions of the shadow are often found alongside the insectile Buzzers, and its seems that this relationship has not been without concessions. Buzzers apparently plant their eggs in virtually anything organic within convenient range. This is the best explanation we have for why juvenile buzzers have occasionally been observed bursting from the corpses of creatures not normally considered part of the Buzzer hive. You can anticipate it by listening out for the muted hum emitted by the younger buzzer as it struggles to escape its place of gestation.