If you have been given an injection even once, you owe your life to North American merostomata.
Extracts of its blood are used for the testing of medical materials such as medicines, vaccines and artificial kidneys.
They are not needed to be killed for getting their blood, only reaping of blood is sufficient.
Even when 30 percent of their blood is taken, they can recover themselves in a short time.
They are not crabs, in fact not even crustacean. Their species is more close to ticks, scorpions and spiders.
They are the last living members of Xiphosura, once a rich species.