Sheep Blowflies Research Articles

SHEEP BLOW‐FLY INVESTIGATIONS

SHEEP BLOW‐FLY INVESTIGATIONS

SHEEP BLOW‐FLY INVESTIGATIONS

Annals of Applied BiologyVolume 28, Issue 3 p. 261-272 SHEEP BLOW-FLY INVESTIGATIONS IX. ON SOME PHYSICAL ASPECTS OF SHEEP DIPPING The Late R. P. Hobson B.Sc., Ph.D., The Late R. P. Hobson B.Sc., Ph.D. Department of Agricultural Zoology, School of Agriculture, University College of North Wales, BangorSearch for more papers by this author The Late R. P. Hobson B.Sc., Ph.D., The Late R. P. Hobson B.Sc., Ph.D. Department of Agricultural Zoology, School of Agriculture, University College of North Wales, BangorSearch for more papers by this author First published: August 1941 https://doi.org/10.1111/j.1744-7348.1941.tb07558.xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume28, Issue3August 1941Pages 261-272 RelatedInformation

Imperial Veterinary Conference

AN Imperial Veterinary Conference will be held at the Royal Veterinary College, Camden Town, London, N.W.1, on August 15–19. The subjects to be discussed will include the work of the Imperial Bureau of Animal Health, foot-and-mouth disease and certain other virus diseases, Johne's disease, bovine mastitis, caseous lymphadenitis of sheep, sheep blowflies, fowl paralysis and chronic bovine haematuria.

Gilruth's Part in Sheep Blowfly Research

Gilruth's Part in Sheep Blowfly Research

Studies on the Influence of the Environment on the Sheep Blow-fly, Lucilia sericata Meig

Prepupae and pupae are shown to lose weight more rapidly at low than at high humidities. This more rapid loss of weight is due to loss of water alone and not to loss of dry matter.The limits of temperature and humidity which each of the two stages can survive have been mapped out. If the metamorphic period as a whole is considered, it is likely that the limits of temperature and humidity for survival and development will be narrower than for each stage considered alone.

SHEEP BLOWFLY INVESTIGATIONS

Summary. Various putrefying substances attract Ludlia sericata to oviposit on sheep in the field. Other blowflies do not respond. Excreta of Ludlia larvae are extremely attractive; faeces from scouring sheep, stale urine and bacterial cultures are also effective. Ludlia does not oviposit on these substances unless they are placed close to the skin of a live sheep; neither sheep skin, wool, nor other live animals can take the place of sheep. The attraction is not due to chemical or bacterial changes in the fleece, since actual contact with the skin or wool is not necessary. It is therefore concluded that the sheep itself plays an essential part in attracting Ludlia. The natural odour may be responsible. These results are discussed in relation to the origin and control of sheep strike.

SHEEP BLOWFLY INVESTIGATIONS

Summary.The present paper is intended as the first of a series dealing with various aspects of the sheep maggot problem, especially the causes of susceptibility. Since this pest is more common in moist weather, an investigation was made of the effect of humidity on sheep maggots; also, a method was devised for studying the humidity at the base of the wool–the site of attack.The following is a brief summary of the results obtained: The eggs and young larvae of Luclia sericata Mg., the sheep maggot fly, are extremely sensitive to desiccation at 37° C. Dry conditions prevail in the fleece near the skin, except in the region of the rump, and the relative humidity seldom exceeds 70 per cent., even during wet weather. These results show that the microclimate at the base of the wool is normally too dry for the development of maggots; this has been confirmed by finding desiccated eggs and larvae on sheep in the field. Sheep do not become infested with maggots unless predisposing conditions are present; the humidity at the base of the wool appears to be the main factor which determines susceptibility. The wool around the rump is often moist owing to soiling with faeces and urine, the humid conditions favouring the development of eggs and maggots.

The Sheep Blowfly Problem in North Wales

Summary.1. Early writings indicate that attack by sheep blowflies was common and well known in the early sixteenth century, prior to the establishment of sheep farming in North Wales.2. A survey of North Wales has shown that Lucilia sericata Mg. is the sheep blowfly of the province. In two advanced cases only were larvae of Calliphora erythrocephala Mg. present, and then only in small numbers.3. Sheep are attacked from May until October. The degree of attack as indicated in a summary of seasons regarded as severe was as follows: Upland districts—10–15 per cent. of sheep attacked; Lowland districts exposed—20–25 per cent.; Lowland wooded—35–40 per cent.4. The complete absence of parasitism among larvae taken from living sheep was a signscant result of the survey. Such a source of unparasitised larvae will mitigate success in the biological control of blowflies.5. The life history of Lucilia sericata under North Wales conditions has been investigated. Four generations are recorded. The normal mode of hibernation is in the prepupal stage, which hibernates in late September or October and returns to the soil surface from mid‐March onwards, when the soil temperature at 8 in. approaches 45° F. and when in the upper layers is slightly higher.6. Shepherds, normally, “rub out” larvae from infested sheep, assuming that starvation and death results in the soil. Over 90 per cent, of such larvae produced imagines, and such infestations are pure cultures of Lucilia sericata Mg. with an absence of competitive secondary species. Experiments, combined with a morphological study, showed that at the temperature of the sheep's body, larvae attain the third instar in 24 hours. They are then only half‐size, but can successfully produce imagines despite subsequent starvation. The present practice, therefore, should be changed, and a larvicide applied before the larvae are removed from the wool.7. There is clear evidence of the greater susceptibility of lambs to attack, and the factors involved are being studied.8. Observations have been made on the relative susceptibility to attack of six different breeds of sheep and their crosses. The degree of attack ranged from the Wiltshire breed, which is only rarely attacked, to the Southdown breed, which is frequently subject to heavy infestations.

Blowflies

OF the hundreds of flies that are encountered daily, few are so well known as the blowflies. Everywhere they are known by their association with carrion. Were they specific in their choice of carrion as food, they would not be the subject of critical research of an army of highly qualified entomologists and veterinary officers scattered throughout the world. It is as a serious menace to sheep and to the wool and the meat industries that blowflies demand most careful study. What then has caused their attack upon live animals? Have they changed their habits? A negative answer to this question is but one of the many interesting and valuable contributions in a recent report on The Sheep Blowfly Problem in Australia edited by Dr. R. J. Tillyard and Dr. H. R. Seddon.