Violin beetle

The Violin Beetle is an insect that appears in, and. They appear first in June, between 4 AM and 7 PM. They reappear in September and October, from 4 AM to 5 PM, and then disappear in November, when they can be found from 8 AM to 5 PM. They can be found on tree stumps of regular and cedar trees, and are uncommon.

Donating to the museum
As with all insects in the, the Violin Beetle can be donated to the museum followed by a small talk by Blathers.

In
After the player has donated a Violin Beetle to the museum, Blathers will say this:

The Violin Beetle can be found on the tree stump, located on the middle level of the insect section.

In
Upon being donated, the beetle can be found in the left-hand back room of the bug exhibit, sharing a large tree stump with the Longhorn Beetle. The exhibit has this to say about the Violin Beetle:

In
When donated, the violin beetle can be found in the main room of the bug exhibit, on a tree stump to the left of the northernmost bridge.

Real-world information
According to the in-game encyclopedia, "These resemble violins-- hence the name. They are so thin, they fit in wood gaps."

Mormolyce phyllodes, commonly known as the, is a species of ground beetles in the subfamily Lebiinae. These beetles possess a flat leaf-shaped, shiny black or brown body with distinctive violin-shaped translucent elytra (hence the common name). This characteristic mimicry protects them against predators, while their flat shaped body allow them to dwell in soil cracks or under the bark and leaves of trees.

Both adults and larvae are predators, feeding on insect larvae. For defense purposes, they secrete the poisonous butyric acid.