The Female Beetle is one of the 24 Golden Bugs in Twilight Princess. Its male counterpart is the Male Beetle. This bug can be traded to Agitha for a Rupee prize.
The Female Beetle is located in the part of Hyrule Field north of Faron Woods. The Male Beetle is also located around here.
Female Beetle's location in Hyrule Field
Male and Female Beetle's locations on the map