copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified sternites on the second abdominal segment. In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a spermatophore) into the female's reproductive tract. Bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species are also known to engage in same-sex sexual behaviors. In these animals, the use of sexual intercourse has evolved beyond reproduction to apparently serve additional social functions (such as bonding). See also Human sexual response cycle Mammary intercourse References External links The International Encyclopedia of Sexuality Janssen, D. F., Growing Up Sexually. Volume I. World Reference Atlas Introduction to Animal Reproduction Advantages of Sexual Reproduction Synonyms for sexual intercourse – the WikiSaurus list of synonyms and slang words for sexual intercourse in many languages Fertility Interpersonal relationships Human reproduction Mating Sexology Intercourse Health risk