Some kind of fly, gnit, gnat, tick or flea of some kind...the desert kind.
Old English gnætt "gnat, midge, mosquito," earlier gneat, used of various small, flying insects, from Proto-Germanic *gnattaz (cf. Low German gnatte, German Gnitze); perhaps literally "biting insect" and related to gnaw.
The gnatte is a litil fflye, and hatte culex..he soukeþ blood and haþ in his mouþ a pipe, as hit were a pricke..And is a-countid a-mong volatiles..and greueþ slepinge men wiþ noyse & wiþ bytinge and wakeþ hem of here reste. [John of Trevisa, transl. of Bartholomew de Glanville's "De proprietatibus rerum," 1398]
Any of various small, biting, two-winged flies, such as a biting midge or black fly.
only in Matt. 23:24, a small two-winged stinging fly of the genus Culex, which includes mosquitoes. Our Lord alludes here to the gnat in a proverbial expression probably in common use, "who strain out the gnat;" the words in the Authorized Version, "strain at a gnat," being a mere typographical error, which has been corrected in the Revised Version. The custom of filtering wine for this purpose was common among the Jews. It was founded on Lev. 11:23. It is supposed that the "lice," Ex. 8:16 (marg. R.V., "sand-flies"), were a species of gnat.