Phasia hemiptera flies are strongly sexually dimorphic. 
The males are more colourful and have broad curved patterned wings with markings of various colors. 
Sometimes the wings show an iridescent blue-black band starting from the front edge, but they may also be completely dark. 
Females have narrower and more transparent wings without markings.

As in most other Tachinid Flies, males can be easily identified by their holoptic eyes (eyes touching at the top of their heads).

Like most tachinid flies, the female lays her eggs on other insects, the larvae then develop inside the living host, devouring it and eventually killing it.
Its main hosts are the Red-Legged Shield Bug (Pentatoma rufipes) in the spring, and the Green Shield Bug (Palomena prasina) in the autumn.

A male. Pfänder Mountain, Bregenz, Vorarlberg, Austria, 2 August 2020