From Nookipedia, the Animal Crossing wiki
When approached in City Folk, it has an aggressive position.
Donating to the museum
In Animal Crossing
"Ah yes, the infamous mantis...Tell me, does it seem to you that it's almost TOO aware of us? Like it's studying us...It's rather as if it were questioning our reason for existence, eh wot? It's eyes...They're far too judgmental. Additionally, the manner in which it uses its scythe-like forelegs to kill and feed...So very vivid! So graphic! Blech! Grisly little beast!"
In Wild World
"I imagine you'll think I'm having a bit of fun, but I assure you, I am serious... After mating, the female mantis will kill the male and devour him on the spot! Blech! The very thought gives me the gags! I must say, I consider myself most fortunate not to have been born a mantis. Hoo, I might have had to squash myself..."
In City Folk
"Tell me, <Player>, have you ever seen the egg case of a mantis? It's not much to look at really. Just a little sack about the size of your fist. It's not even all that vile... But come spring, it bursts asunder and hundreds of baby mantises spring forth! I daresay my issues with bugs began when one such egg case ruptured within my desk. The horror..."
The Mantis can be found towards the back of the museum, perched on the rose on the upper terrace.
In New Leaf
Upon being donated, the Mantis can be found in the room of the bug exhibit with the light in, resting on some flowers near the light. The exhibit has this to say about the Mantis:
"Mantises are known for the praying pose they sit in while ambushing unsuspecting prey. They'll snatch whatever is moving nearby and can even capture creatures larger than themselves. When threatened, mantises will spread their thin green wings to appear more intimidating."
When the player has caught a mantis, they can find information about the insect in the bug menu. Below is the information regarding the mantis:
Mantids can be traced back to over 35 million years ago, and are related to cockroaches. They can be found across temperate and tropic areas all across the world, and can fly. They are strictly carnivorous, and rarely think twice about attacking larger animals.
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