Green’s Dictionary of Slang

1. (Aus.) an officious person; thus blowflyism, officiousness, ‘red tape’.

[1869		Sportsman (London) 14 Jan. 2/2: Notes on News [...] [W] are asked to believe by this blowfly on the skirts of a great reputation].
1895		Truth (Sydney) 31 Mar. 5.1: Government House where, as is well known, Society’s butterflies and blowflies most do congregate.
1899		Bulletin (Sydney) 26 Aug. 16/2: Police are sometimes called ‘blowflies’.
1904		Sydney Sportsman (Surry Hills, NSW) 20 July 3/4: Asked ‘The Trier’ [...] why he didn’t ‘break’ a ‘blowfly’ that is always pestering him and forcing his undesirable company on him.
1918		Truth (Sydney) 28 July 7/1: The spurious form of One-Big-Unionism favoured by some of the A.W.U. officials (which has been aptly named ‘Blowflyism’).
1918		Truth (Sydney) 15 Dec. 6/6: Under the rules of the Blowflies, the A.W.U. [...] would really be ‘an industrial blowfly’, a most serious parasitical pest to the people and a menace to democracy .

2. (US) a boaster.

1965–8

in DARE.