Asexual reproduction
From Memory Alpha, the free Star Trek reference
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only.
Tribbles were bisexual (dual sexed) and were capable of reproducing at will. Born pregnant, and with sufficient food, a single tribble could breed in number exponentially, producing a litter of ten in twelve hours time. (TOS: "The Trouble with Tribbles") Xindi-Insectoids also reproduced asexually. (ENT: "Hatchery")
