The aptly-named mayfly orchid is considered locally common in some parts of its native eastern Australia. That said, it is never so abundant as some species of its namesake: “The 2014 hatch of the large black-brown mayfly Hexagenia bilineata on the Mississippi River in the US was imaged on weather radar; the swarm flew up to 760 m (2500 feet) above the ground near La Crosse, Wisconsin, creating a radar signature that resembled a “significant rain storm”, and the mass of dead insects covering roads, cars and buildings caused a ‘slimy mess'” (mayflies via Wikipedia).
The scientific name also aligns. Aci- means “pointed” or “sharp”, -anthus means “flower”, and caudatus means “tailed” (having a tail). From the tip of the pointed dorsal (upper) sepal to the lateral (lower) sepals, the musty-smelling flower measures approximately 7cm (~2.75 in.) in height. These are borne atop a single-leaved stem that is about twice the height of the flower (Wikimedia Commons has an image of plants in habitat).
The Seeds of Australia Acianthus caudatus page has a number of additional images, while the Flora of Victoria entry for Acianthus caudatus has a good description of its habitat: “occurring in cool shaded positions in light forest but abundant only in sandy areas near-coast”.