oxidation of dipping fluids in the vat. It was found that formaldehyde 

 solution (37 per cent.) used in the proportion of 1 gal. to every 1,500 

 gals, of fluid in the vat was a safe and effective means of reducing 

 oxidation to a low figure. Since there seems to be no evidence that 

 oxidation is ever likely to progress so far as to result in injury to cattle, 

 the question of the use of formaldehyde is purely an economic one. 

 In most cases it will probably be cheaper to allow some of the arsenic 

 to be wasted by oxidation. 



BiSHOPP (F. C). Fleas.-- C/.aS. Dept. Agric., Washington, D.C., Bull, 

 no. 248, 14th August 1915, 31 pp., 9 figs. 



Fleas in the adult stage are almost exclusively parasitic on warm- 

 blooded animals. Adults normally feed once a day or possibly oftener. 

 Certain species show a marked tendency to infest certain portions of 

 the host, and in the case of inoculation of an animal with plague bacilli 

 by a flea, it has been observed that there is a relationship between the 

 point of attack and the formation of the swellings. The number of 

 eggs deposited by a single female varies with the species, the abundance 

 of food and climatic conditions. The egg-stage lasts from 2 to 12 days. 

 The food of the larvae of nearly all species consists partly of blood 

 voided by the adult, partly of particles of animal or vegetable origin. 

 The total period from the deposition of the egg to the emergence of 

 the adult, in tests with the dog flea conducted during the summer at 

 Washington, ranged from 17 to 35 days. A table showing the relative 

 lengths of the life-cycle of fleas in different countries is given. This 

 duration is influenced by food, temperature and humidity. [See this 

 Review, Ser. B, ii, pp. 62-64.] In nearly all cases breeding places are 

 closely associated with the resting places of the host. A marked 

 seasonal variation is shown in the abundance of fleas in any country. 

 In the United States human fleas are prevalent during the summer. 

 In India there is a marked decrease in numbers at the approach of the 

 hot season. Variation from year to year is due to weather conditions ; 

 in the United States years of greatest abundance may coincide with a 

 summer rainfall which is above the normal. In those portions of the 

 country where mild winters and comparatively humid summer con- 

 ditions prevail, fleas are most abundant. Sandy soil is most suitable 

 for breeding, as it provides the most uniform conditions of moisture. 

 The movements of fleas are of little importance in spreading the species. 

 Dispersal is effected by the movement of the host, by the scattering 

 of the eggs and by the carriage of adults or immature stages in 

 merchandise. 



The following species are capable of carrying bubonic plague :— 

 XenopsijUa cheo2yis, Roth. (Indian rat flea), Ceratojjhyllus fasciahis, 

 Bosc. (European rat flea), Pidex irritans, L. (human flea), Leptopsylla 

 musculi, Duges (European mouse flea), Ctenocephalus cams, Curtis 

 (dog flea), C. felis, Bouche (cat flea), Hoplopsyllus anomalus, Baker, 

 and Ceraiojjhylliis acutus, Baker (squirrel fleas), C. anisus. Roth., and 

 Pygiopsylla ahalae, Roth, (rat fleas). The human flea is largely 

 dependent on man as a host, although in Europe it seems to thrive 

 on the badger and in the United States is commonly found on the 

 skunk. Pigs and rats also serve as temporary hosts. EcJiidnophaga 

 gaUinacea (chicken flea) is widely distributed in the tropics and warm 



