In the wild, they attack chiefly the nostrils and pharyngeal cavity of moose (also known as elk in Europe), but have been found in other deer species.

There have also been several cases of C. ulrichii squirting their larvae into the eyes of human beings, a somewhat painful event that requires medical attention to forestall any possibility of serious damage.

The adult C. ulrichii botfly is 16–18 mm long, its body covered with fluffy hairs of yellow, black and white, making it look like a bumblebee.

In sunny weather, from July to September, females seek out an appropriate host site, typically the nostrils of a moose, and forcefully eject larvae onto its surface.

[1] C. ulrichii are common parasites of moose in northeastern parts of Scandinavia, but have recently expanded their range into southern Sweden.