Five species of bee-like flies belonging to the genus Cephenemyia have been reported from North America.  The larval stages of these flies are the grubs, bots or maggots found in the nasal passages and throat pouches of cervids and are specific to these hosts.

In Ontario, the most important member of the genus is Cephenemyia phobifer whose larvae parasitize principally deer but also moose.  Sixty-two percent of 322 deer examined from Algonquin Park from 1949-1961 were infected with C. phobifer (Bennett, 1962).  The known distribution of the parasite in Ontario extends generally throughout the deer range.

The life history of C. phobifer is not fully known.  However, Bennett (1962) showed that the adult flies, having no mouth parts, cannot feed and consequently live for only a short time.  Golini et al. (1968) reported that the adult female fly, while in flight, deposits larvae into the nostrils of the cervid host during hot days of summer.  The early stages of larval growth take place within the nasal cavities.  After a limited amount of development in this site, the larvae then move to the retropharyngeal pouches which lie on either side of the throat at the base of the tongue.  Here the greatest amount of growth takes place.  Fully developed larvae are about 25-36 millimetres in length and at maturity are expelled from the throat to pupate in the soil.  Following a relatively short pupal period of 2-3 weeks, the adult flies emerge and the cycle is repeated.  Members of the genus overwinter in the larval stage within the cervid host.

With age the larvae vary in colour from whitish-yellow in the early stages to brownish-yellow to dark brown just prior to pupation.

Following the death of an infected animal, the larvae migrate from the throat pouches and consequently may be found in the trachea, bronchi, oesophagus or stomach.  The retropharyngeal pouches are, however, the normal location of the larvae.  As many as 42 larvae have been found in one pouch.  The results of Bennett's work in Ontario indicated that other than causing a local inflammation in the infected pouches, the larvae did not appear to produce any effect upon the host.  However, Golini et al. (1968) observed that penned deer snorted frequently and lost nasal fluid during periods when adult C. phobifer were collected near them.

Other cervids in Europe have been observed to react violently to the presence of other species of Cephenemyia, sometimes burying their heads in vegetation or striking at adult Cephenemyia with their hooves.  White-tailed deer have not been observed to actively avoid C. phobifer in this manner.

Selected References:

Bennett, G.F. 1962.  On the biology of Cephenemyia phobifera (Diptera:Oestridae), the pharyngeal bot of the white-tailed deer, Odocoileus virginianus.  Can.  J. Zool. 40:1195-1210.

Golini, V.I., S.M. Smith and D.M. Davies. 1968. Probable larviposition by Cephenemyia phobifer (Clark) (Diptera:Oestridae).  Can.  J. Zool. 46:809-814.