Crickets are known for their chirp (which only male crickets can do; male wings have ridges or "teeth" that act like a "comb and file" instrument). The left forewing has a thick rib (a modified vein) which bears 50 to 300 "teeth". The chirp is made by raising their left forewing to a 45 degree angle and rubbing it against the upper hind edge of the right forewing, which has a thick scraper (Berenbaum 1995). This sound producing action is called "stridulation" and the song is species-specific. There are two types of cricket songs: a calling song and a courting song. The calling song attracts females and repels other males, and is fairly loud.