Mr Sweet

"Mister Sweet" was the wholly fictitious name that Winifred Gillyflower gave to a red leech she discovered in the year 1893. He resided on Gillyflower's chest, giving her his nectar. He was immediately recognised by Madame Vastra as being from the late Cretaceous Period, and a known menace to the Silurians. When Strax killed Gillyflower and he tried to escape, Ada Gillyflower killed him with her walking stick. (TV: The Crimson Horror)