Beetle

Beetles were Earth coleopterans. K9 once encountered one on a planet in another dimension, partially inhabited by ex-Tellac miners. They lived alongside other Earth animals from widely varying periods of evolutionary history. Unlike most species of beetle on modern Earth, however, these may have been the size of horses, as many extinct species were on Earth in the prehistoric past. (PROSE: K9 and the Missing Planet)

On visiting East Sussex in 1912, the First Doctor's companion Vicki Pallister expressed a desire to visit London and see the Beatles, not realising that she was decades too early. This led Constance Arden to believe that she was a keen coleopterist, given her apparent interest in beetles. (AUDIO: The Suffering)

The Fourth Doctor believed that the dye used to make red jelly babies came from crushed Mexican beetles. (PROSE: Ghost Ship)

Jack Harkness refered to Mother Nothing as a giant beetle. (AUDIO: One Enchanted Evening)