Solo performances in gay pornography have been described in 1985 as either or both active and/or passive , whereas female solo performances hentai sex are said to be exclusively passive . A homosexual threesome would involve either three men or three women. Women who perform in lesbian pornography often do not consider themselves lesbian gay boy porn or bisexual. Preggo pornography features pregnant performers and may include erotic lactation as a fetish. Sex parties may be organized to enable people to engage in casual sexual activity or for swinging couples or people interested in group sex to meet, but any gathering where sexual activity is anticipated can be called a sex party. Animal masturbation has been observed in many species, both in the wild and in captivity. Sigmund Freud considered foot binding as a form of fetishism. Sexologist Alfred Kind suggested that the buttocks is the primary sexual presentation site in primates. Macrophilia is a fascination with or a sexual fantasy involving giants, more commonly expressed naked milf as giantesses . Sexual orientation Pornography features an increasing variety of combinations of actors by their sexual orientation such as lesbian, gay, bisexual, and transsexuals in addition to traditional heterosexual roles. Bukkake is a sex act portrayed in pornographic films, in which several men ejaculate on a woman, or another man. The niche popularity grew significantly in the latter half of the first decade of the 2000s. This can, however, redirect semen into the bladder . There are number of types of sex parties: Swinger party/gathering A swinger party or partner-swapping party is a gathering at which individuals or couples in a committed relationship can engage in sexual activities with others as a recreational or social activity. Older names for a pornographic film include stag film, and blue movie. If this is done using penises and/or strap-on dildos, this is sometimes called the sandwich or BigMac. Since development and pronunciation of the buttocks begins at menarche and declines with age, full buttocks are also a symbol of youth.