CEPHENOMYIA SP. KILLING DEER

Distribution, prevalence and intensity of moose nose bot fly (Cephenemyia ulrichii) larvae in moose (Alces alces) from Norway

High host density combined with climate change may lead to invasion of harmful parasites in cervid (host) populations. Bot flies (Diptera: Oestridae) are a group of ectoparasites that may have strong impact on their hosts, but data on the current distribution, prevalence and intensity of the moose nose bot fly (Cephenemyia ulrichii) in Scandinavia are lacking. We estimated prevalence and intensity of nose bot fly larvae in 30 moose from southern and 79 moose from central Norway. All larvae detected were identified as the moose nose bot fly. We found surprisingly high prevalence in these areas, which are up to 1300 km south-southwest of the first published location in Norway and west of the distribution in Sweden. Prevalence (0.44-1.00) was higher in areas with higher moose density. Parasite intensity in hunter killed moose was higher in central Norway (mean 5.7) than southern Norway (mean 2.9), and in both regions higher in calves and yearlings than adults. Fallen moose had higher parasite intensity (mean 9.8) compared to hunter killed moose in the subsample from central Norway, suggesting a link to host condition or behavior. Our study provides evidence of parasite range expansion, and establishing monitoring appears urgent to better understand impact on host populations.

The Nasal Bot Fly, Cephenomyia auribarbis Meigen (Diptera, Tachinidae) of the Red Deer, Cervus elaphus L

1. Cephenomyia auribarbis Mg., a tachino-oestrid parasite of the red deer (Cervus elaphus L.), is distributed throughout the deer forests of Scotland. The adult is found on the wing during June and July.

2. The larva normally occurs attached to the walls of the nasal passages and pharynx, where it remains for 10 or 11 months. At maturity it drops to the ground and pupates beneath the surface. The adult emerges in 3–4 weeks.

3. In January, 1931, a larva of the early third instar was recovered from a stag shot at Blair Atholl, Perthshire. It was found in fat in the pelvic region and not in the nostril or pharynx as might have been expected.

4. It is suggested that the larva may have been swallowed by the host and bored its way through the wall of the gut into the peritoneal cavity, whence it had wandered to the pelvic region; or else that a first-stage larva had been accidentally deposited by a female on the hide and had bored through the body wall to the peritoneal cavity.

5. The adult female and the early third-stage larva are described and illustrated.

6. A comparison is made between the cephalo-pharyngeal apparatus of Cephenomyia auribarbis, Cephalomyia ovis, and Gastrophilus intestinalis. It is noted that the basilar sclerite of the first two species is provided with an accessory lateral appendage on each side. A greater surface is thus furnished for the attachment of the large depressor muscles of the buccal hooks. The larva thus securely holds its ground in the nasal cavities and pharynx, where the risks of summary ejection are always present. In G. intestinalis the accessory appendage is absent. The chances of the larva of this species losing its hold on the gastric mucous membrane of the host are very slight.

ON THE BIOLOGY OF CEPHENEMYIA PHOBIFERA (DIPTERA : OESTRIDAE), THE PHARYNGEAL BOT OF THE WHITE-TAILED DEER, ODOCOILEUS VIRGINIANUS

Examination of 322 deer in Algonquin Park, Ontario, during 1949–1961, has shown that 62% of the animals harbor Cephenemyia phobifera. Most parasites were found in deer 6 months to 2 years of age and fewer in those 6 months or less. Deer from herds harbored more bots than non-herd deer. Deer from second-growth forests were more heavily parasitized than deer from mature deciduous forests. Data on the incidence of infestation and the occurrence of the various larval instars in deer examined at different periods throughout the year strongly indicated that phobifera has two generations per year: the winter cycle requires about 6 months, the summer cycle 3 months. Puparia of phobifera metamorphosed in 23 ± 1 day at 63 ± 5° F, in 15 clays at 77 ± 2° F. Adults were short-lived. Deer blood was found in the alimentary tracts of the larvae examined. Presence of the larvae caused enlargement of the retropharyngeal pouch, and destruction of the epithelial layers.