Mantis

The Giant Mantis is the main antagonist in the Scooby-Doo Show in the episode Creepy Creature From Vulture's Claw. The Giant Mantis turned out to be a costume by Proffeser Grear. The Giant Mantis was 1st seen coming out of the ferns and chases the Mailman. When Scooby gave the flowers to the Giant Mantis, the Giant Mantis sneezed. Proffeser Grear told the gang about the Praying Mantis. The Giant Mantis continues to chase the gang, he even taken Daphne hostage. The Giant Mantis was actually Proffeser Grear after he was captured.

Trivia
The Giant Mantis was 7 feet tall (said by Shaggy)

Proffeser Grear must have been allergic to flowers because he was the Giant Mantis and he sneezed from the flowers.

How could Proffeser Grear be so tall when he was chasing the Mailman?

Now Proffeser Grear has the right size when he chases the gang.

The Gang called the Praying Mantis creature the Mantis instead of the Giant Mantis.

The Giant Mantis's roars sound like Gator Ghoul's who was seen in Grusome game of the Gator Ghoul.