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implicated in these cases. Pigs, goats, sheep and cats are frequently 

 attacked, but all these domesticated animals were first introduced into* 

 tropical America from Europe at the beginning of the sixteenth century^ 

 and though now important as hosts and reservoirs of the parasite, 

 the original and normal hosts are the indigenous wild fauna. Z). hominis- 

 has been found in monkeys, pumas, the red brocket {Cariacus rufiis} 

 and in agoutis, in the warty skin of the head and neck of turkeys 

 and in certain species of toucan and ant birds. It was reported to 

 the author in Trinidad that poultry were also attacked, but the birds 

 examined were found to harbour the larvae of Mydaea 'pici, Macq., 

 and not those of Dermatobia. The life-cycle of Dermatobia is not per se 

 markedly periodic, but a certain periodicity is introduced by the effect 

 of seasonal conditions on the mosquito intermediary which carries 

 the larvae to the vertebrate host. According to Folkes (1897), the 

 natives of Guatemala regard it as most prevalent in the rainy season, 

 but he himself thinks it is most numerous just after the rains. 

 Goudot (1842) states that in Colombia it is specially prevalent after 

 protracted rainy seasons. Dr. Paez informed the author that it is 

 more abundant in the plains during and after the rains, but that in 

 the woodlands it occurs in nearly the same numbers all the year 

 round, which increases the probabihty of transmission by a Culicid. 

 The warbles are generally to be found in man and cattle from March 

 to September, with a maximum in April, June and July, this period 

 corresponding more or less with the rainy season of the fly area in 

 Mexico, Central America and the northern parts of South America. 

 In cattle the warbles are found in the head, sides, tail and along the 

 backbone, but principally about the shoulders, i.e., the parts least 

 accessible to the animal's tongue, horns or tail. In man all exposed 

 parts are attacked, but there is some reason for believing that the 

 larvae are ingested and migrate to the exterior, which would explain 

 their appearance in parts not readily accessible from the outside. In 

 no case is there any evidence that the patient was aware that he had 

 been bitten by the fly, and some reliable observers, though attacked, 

 never had an opportunity of seeing a single specimen of the perfect 

 insect. Direct oviposition cannot however be excluded, for, according 

 to Dr. Lutz, the fly hovers round man, horses or cattle with the ovi- 

 positor exserted. In Venezuela the natives believe that the larvae 

 crawl on to the body from the ground ; in other places the fly is 

 thought to oviposit on hnen which has been left to dry after sunset, 

 and over the whole area there is a belief that the fly oviposits on the 

 leaves of certain plants especially on the borders of narrow paths. 

 The natives, especially in Brazil, attribute the warbles to the bite of 

 a mosquito. The connection with a mosquito was demonstrated by 

 Dr. R. Morales of Guatemala, in 1911, to whom a collection of mosquitos 

 had been sent. Amongst these was a large species specially labelled 

 as the carrier, from which a larva was successfully introduced into 

 the forearm of an assistant. The work of Drs. M, Nunez Tovar, 

 R. G. Rincones, and J. Surcouf is also mentioned in this connection 

 [see this Review, Ser. B. vol. i, p. 106]. The species most commonly 

 selected as a carrier of the eggs is Janthinosoma lutzi, Theo., but it is 

 more than probable that other species and even other Diptera may 

 at times serve the purpose. The time of residence of the larva in 

 the skin of the host is variable, and such evidence as there is, points 

 (C189) A 2 



