These insects are used as potion ingredients (see). They are small insects with large, transparent wings. Lacewing flies eat aphids.
A small slug-like creature that lives in water. Leeches attach themselves to other creatures and suck their blood. Leeches are used as potion ingredients, both sliced and in the form of leech juice.
XXX - Ireland
A tiny vegetarian creature resembling a little (maximum height 6 inches) green human, the leprechaun is one of the occasional anomalies of the beast/being classification system. Although they alone of the "little people" have the ability to speak human language, they are classified as beasts, and have remained in that category as they have never requested re-classification (although they appear to have made no political statement by this, unlike centaurs and merpeople. They are able to produce a gold-like substance that vanishes after an hour or two (GF8, GF28). Leprechauns are the Irish National Quidditch Team's mascots (GF8).
This dangerous beast resembles a half-inch thick black cloak which moves along the ground at night, hunting its prey. It attacks sleeping humans, smothers them, then digests them, all in their bed, leaving no trace at all. The only known defense against a lethifold is a Patronus Charm. Thankfully, this frightening creature is rare, only found in the tropics (FB).
L. lethum, variation of letum, death (NSOED) + "fold," suggestive of cloth
XXXXX - China
XXXX - Scotland
The largest known and most famous kelpie on Earth; this monster makes its home in Loch Ness, usually in its favourite form of a sea serpent (FB). The Department for the Regulation and Control of Magical Creatures has been trying to find a way to hide the Loch Ness Monster, who is notorious for showing off for Muggles. Hagrid at one point offered to keep the giant kelpie in the Hogwarts lake (DP1).
XXXXX - Romania