Scarabs are flying insects made of gold. They are unique amongst creatures in Spelunky in that they are completely harmless, and collected as treasure when touched.
They only appear in dark levels and the City of Gold.
Scarabs flee from the player and produce bright but narrow radius of light in dark levels, making them easy to find in the darkness.
You must treat them carefully when trying to collect them. If they take any damage, they will be destroyed and you will lose the chance to gather them as treasure. Luckily, they don't take damage from being stomped on like most enemies, so you don't need to worry about touching them from above.
It's also possible to carry Scarabs like items or enemies, but they are rarely found at ground level so it's not always possible to do so. If a Scarab is thrown while being held, the player will collect it, and it will be left behind if the player leaves the level while holding the Scarab.
Like all other forms of treasure, Scarabs increase in value in later areas.