The hyaline wings are tinged with gray on nearly the entire costal half, except sometimes having a spot toward the apex of the submarginal cell.

Although the oil can reach temperatures of up to 38 °C (100 °F), the larvae suffer no ill effects from it, even when additionally exposed to 50% turpentine or 50% xylene in laboratory experiments.

Oil fly larvae contain about 200,000 heterotrophic bacteria, which have been of interest to scientists searching for microorganisms or enzymes that function in an organic solvent environment.

The nitrogen-rich nutrients released into the gut make the environment, with a pH of around 6.5, suitable for the development of these bacteria.

[6] William Homan Thorpe referred to H. petrolei as "undoubtedly one of the chief biological curiosities of the world.