99 



apparent choice of host is mainly a question of its body tem- 

 perature. Rats are readily attacked; in guinea-pigs, the larvae 

 almost always abort ; in pigs, the development of the larvae was 

 arrested in a day or two, and in fowls, it failed entirely. Larvae 

 placed on fresh raw meat refuse to feed ; in a dry atmosphere they 

 may live for 10 or 11 days, if moist, barely 6 days. The larva, 

 whether freshly emerged or 8-10 days old, penetrated the skin 

 immediately, boring obliquely between the epidermis and the dermis, 

 the process occupying about half an hour ; once removed from the 

 tumour the larva is incapable of repeating the operation. The first 

 moult takes place in about three days after penetration and the total 

 period of residence ^\ithin the host is 7 to 8 days. Upon emerging, the 

 larva falls to the ground and buries itself, remaining for 2 or 3 days 

 without change, and consuming its reserves of food ; it then pupates, 

 the pupal stage never lasting more than 20 days. High temperature, 

 such as 35^ C. (95° F.), appears to be fatal. 



Oestrus ovis, L., is very common in West Africa and causes great 

 loss among sheep. The loss is apparently aggravated by the sudden 

 fall of temperature at night, and it strongly advised that only those 

 breeds of sheep which are more or less accHmatised, should be kept. 

 The dust and dirt of the native stock-yards greatly increases the suffer- 

 ing of the animals. Oestrid larvae, probably those of Rhinoestrus 

 nasalis, de Geer, are said to be frequently found in the frontal sinus 

 in cattle in the abattoirs at Daka. Cephalomyia maculata, Wied., 

 has been found in the pharynx of camels. Larvae, probably a species 

 of Rhinoestrus, are occasionally found in the nasal fossae of horses 

 in Senegal, and they have been found also in a duiker, Cephalophus 

 ■melanorheus, Gray. The larvae of Oestrus variolosus are very common 

 in the frontal sinuses of Bubalis major, Blyth. Gedoelstia cristata, 

 in Lichtenstein's haartebeeste ; Kirkia surcoufi, in Bubalus riiajor and 

 Cohus defassa ; and K. blanchardi, are also mentioned [see this Review, 

 Ser. B, li, p. 91]. The following method of rearing Oestrid larvae is 

 recommended ; when taken from the head of a freshly killed animal, 

 they are sorted into two lots, those which are uniformly white and 

 those which show brown or black bands ; the latter are in the third 

 stage and near pupation. These are put into wide-mouthed bottles 

 containing 2 or 3 inches of dry sand and the mouths closed with mushn. 

 After an interval, varying from a few hours to one or two days, they 

 bury themselves in the sand and pupate ; the adults will emerge 

 in about a month. Adult Oestrids cannot be induced to breed in 

 cages, as they take no food and will not mate. The Oestrids which 

 affect horses, mules and asses include a variety of Gastrophila intes- 

 tinalis, which Brauer has named G. asininus ; G. nasalis, L., which 

 is fairly common, is found in the duodenum of horses, rarely in the 

 stomach ; it does not attach itself to the margin of the anus hke 

 G. haemorroidalis ; it is probable that G.flavipes also occurs. Extreme 

 cleanhness and the removal of ova and young larvae from the skin are 

 the only preventive measures of any value. Elephants are attacked 

 by two genera, Pharyngoholus and Cohboldia, the adult fly of the former 

 being as yet unknown. Cobbold described the parasite of the Indian 

 elephant as GastropJiilus elephantis, but Brauer, finding that the larvae 

 had characters distinct from those of Gastrophilus placed them in a 

 new genus Cohboldia, and Blauchard in 1893 discovered that those 



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