Saw stag

The Saw Stag (ノコギリクワガタ, Nokogiri Kuwagata), known as the Saw Stag Beetle prior to is a beetle that appears in all  games. It can be sold for 2,000 Bells.

In Animal Crossing
"They're called beetles, wot? The lugs of the insect world. Insects with armor plating on their backs, you know. Their armor, it...opens up, revealing wings, which they use to fly. It's really quite unnatural. Then, there's that thin membrane-like covering where their heads connect to their bodies. Most foul!"

In
Blathers will comment on the donation to the museum as follows:

"The saw stag beetle's most distinguishing feature is its large, curved jaw, wot? The larger the specimen, the more teeth in its jaw. Among collectors, the teeth settle a specimen's worth. I don't suppose bugs have dentists... Hoo, I'm quite sure that would be the worst job of all time."

After donation, the Saw Stag Beetle can be found on the top tier of the insect section, on the fourth tree from the lantern on the left side.

In
When donating to the museum, Blathers will say the following:

"The saw stag got its name from the shape of its pincers. That is, its pincers look like jagged saws! And I tell you, the bigger the beetle, the more saw-like teeth its giant jaws have. I saw the saw stag seems more at home in a horror film than in nature. I have terrified myself just talking about it. "

Real-world information
The Prosopocoilus inclinatus (Saw Stag Beetle) is one of the most common Japanese stag beetles. They are kept as pets in Japan, much like many other beetles. The mandibles on its head change shape as the beetle grows - the larger it becomes, the greater the angle and size the mandibles become.