What is a Praying Mantis? The praying mantids, or praying mantises, are carnivorous insects that belong to the family. There are about 2,000 species of mantids. The biggest praying mantises are the Tenodera and the Archimantis, which are six inches long! The smallest praying mantis is the Bolbe pygmaea, which is only 2/5 of an inch, or one-centimeter. Unbelievably, some scientists agree the mantis is closely related to the cockroach. The name "mantis" comes from the Greek word for 'prophet' or 'soothsayer.' The Carolina mantid is a common insect of Eastern United States. The European and Chinese species were introduced to the Northeastern United States about 75 years ago as garden predators in hopes of overtaking the native pest population.