Saliva pornography involves salivation and saliva. Lesbianism has been a theme in erotic art since milf xxx at least the time of ancient Rome, and many regard depictions of lesbianism to be erotic. For other scenes, particularly in established relationships, a safeword may be agreed to signify a warning rather than explicit withdrawal of consent; and a few choose not to use a safeword at all. Now facial cumshots are regularly portrayed in pornographic films, videos, magazines and internet web sites. This category also includes pornographic home movies. Lesbian pornography made for women is usually made by women, and usually features women who identify as lesbian or bisexual. Emetophilia pornography involving vomiting and gagging. In addition to mainstream pornography, the popularity of facials has led to creation of its own niche market, like video series that specialize in showing the act. The higher pay scale and profile within a production often leads to group scenes where a straight actor only tops. Transsexual porn star Wendy Williams has stated that transsexual porn is classified as Straight Specialty. In human sexuality, a threesome is sexual activity that involves three people at the same time. Matsuo used amateur actresses in his videos, and he usually traveled to their hometowns for the filming. Generally, interest differs between people, and gender depends on sexual orientation. Although interracial pornography theoretically can apply to depictions of sexual activity between performers of any different racial groups, the term is most commonly used for heterosexual sex acts between black and white performers. When sexual activity is centered on one of the threesome, then the activity may be described as a gang bang of the person. In some societies, the terms fox, plum, chick, or chicken are preferred. It is commonly 3d hentai depicted in pornography, but very rarely in mainstream gay sex video cinema. A variation on this is to place the fingers and thumb on the penis as if playing a flute, and then shuttle them back and forth.