Sometimes one or more fingers may be inserted into the vagina to stroke its frontal wall where the G-spot may be located. What seems clear from the historical record is that much of the lesbian material in pornographic texts was intended for a male readership. Bondage pornography specializes in the depiction of sexual bondage or BDSM activities as photographs, naked milf stories, movies, or drawings. In Canada, Teletoon offers up its own Teletoon at Night programming block. Group sex pornography features at least two men and two women , usually more, who all perform sex acts on each other. The term BDSM dates back to 1969; however, the origin of the term BDSM is unclear and is believed to have been formed either from joining the term B&D with S&M , or as a compound initialism from B&D, D&S , and S&M. Men may also rub or massage the glans, the rim of the glans, and the frenular delta. The term pearl necklace is used by some because the drops of semen deposited by the man resemble a necklace of translucent white pearls. Its gain in prominence has been attributed to its depiction in the film Pecker, which was released in 1998. The niche popularity grew significantly in the latter half of the first decade of the 2000s. Mammary intercourse is a sex act, lesbian hentai performed as foreplay or as non-penetrative sex, that involves the stimulation of the male penis by the female breasts and vice versa. Many transgender people regard the term shemale as offensive, arguing that it mocks or shows a lack of respect towards the gender identity and gender expression of transgender individuals; in this view, the term emphasizes the biological sex of a person and neglects their gender. Double penetration of the vagina, anus and mouth, can involve: Simultaneous penetration of the anus by two penises or other objects. Tentacle erotica can be consensual, but frequently gay fuck contains elements of non-consensual sex. Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates, and not necessarily on the market to which each sub-genre appeals.