115 



Apparently the lack of undercurrent and the smaller amount of oxygen 

 in the dammed water are unfavourable to the flies. Furthermore the 

 larvae pupate on water-plants, and if the water-level falls the adults 

 emerge ; if this emergence takes place in spring when animals at 

 pasture have not been immunised by occasional bites, then fatal cases 

 occur. To prevent the emergence of large swarms it is necesssary to 

 observe the development of the larvae and the height of the water, 

 and the latter must be dammed at the proper time. In the case of 

 small brooks or drains recourse may be had to flooding ; the larvae will 

 migrate to the submerged grass and a sudden fall of the water will 

 leave them to perish. These methods are advocated in conjunction 

 with preventive measures consisting in regulating the times when 

 animals are put out to graze. The latter measures proved very successful 

 in Anhalt, no deaths occurring in 1918 and 1919 in spite of large swarms 

 of Simulium being observed. 



L6pez Neyra (C. R.) & MuNOZ Medina (J. M.). Estudio del Ciclo 

 evolutivo seguido por algunas Especies correspondientes al Genero 



Dvpylidium, Leuckart. [Study on the Development of certain 

 Species of the Grenus Dipi/lidium, Leuckart."] — Bol. R. Soc. Esp. 

 Historia Natural, Madrid, xix, no. 9-10, November-December, 

 1919, pp. 494-506, 2 plates. 



Experimental studies are described on various species of Dipylidiufri, 

 more particularly D. canmuni, L., an internal parasite of the dog and 

 ■domestic cat, and, accidentally, of man. It is known that the 

 intermediary hosts and transmitters that harbour the cisticercoid 

 stage of D. caninum are, accidentally, the louse of the dog, Trichodedes 

 €anis, Retz, and preferably, the dog-flea, Ctenocephalus canis, Curtis, 

 and the human flea, Pulex irritans, L. It has been demonstrated 

 that the larval stage of the parasite develops normally in these hosts, 

 and owing to the small size of the lumen of the proboscis in the flea, 

 which would prevent the insects from ingesting the large eggs of 

 D. caninum, it is admitted that they must become affected in their 

 larval stage, when their mouth-parts are comparatively large. This 

 hypothesis has been proved by the failure to infect adult fleas by 

 feeding them upon dogs infested with eggs of D. caninum, and by the 

 success of infecting flea larvae under the same conditions. The eggs 

 in this case are easily ingested and pass to the intestines, where the 

 embryos remain free, and penetrating into the general cavity, become 

 localised for preference in the last larval segments. Here they remain 

 without development until the fleas become adult. Two or three 

 ■days later, the embryo begins to develop. 



Francis (E.). Filariasis in Southern United States.— Z7./S'. Pub. 

 Health Service, Washington, D.C., Hyg. Lab. Bull. 117, June 1919, 

 36 pp., 10 plates. [Received 6th April 1920.] 



Filariasis of man, a mosquito-borne disease, is characterised by the 

 presence in the blood of microscopic slender microfilariae that are 

 the offspring of adult female worms permanently located in some 

 tissue of the body. In the case of Filaria bancrofti, by far the most 

 widespread species infesting man, the parent worms are located in the 

 lymphatics and lymph glands. Disease is caused by the blocking 



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