While adults of W. magnifica are harmless, their larvae are obligate parasites of warm-blooded vertebrates including humans.
Portschinsky (1916) described many human cases in Russia and warned people not to sleep outside between the hours of 10.00 and 16.00, when the adult flies are active, because of the danger of infestations of the oral cavity as the mouth drops open in sleep, allowing the fly in to lay its larvae.
Deposited by females directly onto the tissues of their hosts, the larvae feed and develop rapidly, moulting twice before reaching maturity, at which point they leave the wound they have created, dropping to the ground to pupate.
The wounds they cause are an example of what is known as traumatic myiasis and they are a source of considerable pain and suffering to hosts, which can die if untreated. Even if the hosts do not die, this parasite is a major animal welfare concern to the livestock industry, affecting: