45 



To regulate with certainty the proper intervals for dipping, it is 

 necessary to ascertain the length of time required for the development 

 of the lice on horses. According to Herms (1915) sucking lice mature 

 in 3 or 4 weeks, and practical experience indicates that two dippings 

 are usually ample. On the other hand, the statement by Herms 

 that these lice hatch in 5-6 days is apparently not true of H. asini. 

 Herms also states that biting lice hatch in 5-8 days, which accords 

 with the author's experience, and mature in 3-4 weeks. Under these 

 conditions horses should be dipped for biting lice twice at intervals 

 of 10-20 days, 2 weeks being probably the safest interval. Where 

 both kinds of Uce are present, an interval of about 20 days appears 

 to be indicated. 



Tests, which are as yet incomplete, indicate that Trichodectes is 

 more resistant to insecticidal treatment than is Haetnatopinus. As 

 sodium fluoride has been found effective against poultry lice and as 

 Trichodectes is also a Mallophagan, handfuls of this substance were 

 rubbed into the coat of an infested horse — with complete success. As 

 was expected, no effect was obtained on horses infested with sucking 

 lice. The fluoride treatment is applicable in winter and apparently 

 does not injure the hair or skin. Other insecticides include coal-tar 

 dips, fish-oil, a 2-3 per cent, watery solution of creolin, a mixture 

 of 1 part petroleum to 10 parts methylated spirit, and grey mercury 

 ointment (not more than 150 grains at one application). Washing 

 the coat with soapy water and then dusting with fine beech or peat 

 ashes is also a useful measure. Other dusting powders that may be 

 used are naphthaline, sulphur, pyrethrum, etc. The author is not 

 convinced by the statement of European investigators that one 

 method of removing the human body louse [Pediculus humanus] 

 from clothing is to put the garments on a horse, though lice thus 

 transplanted " might die of something akin to gastralgia or even 

 nostalgia " ! 



Hadwen (S.). The Life-history of Hypoderma bovis and H. lineatum. 

 — Jl. Awer. Vet. Med. Assoc, Ithaca, N.Y., li, no. 4, July 

 1917, pp. 541-544. 



The principal difEerences between Hypoderma bovis and H. lineatum 

 are tabulated in the first part of this article, which also records obser- 

 vations made at Agassiz, British Columbia, including notes on the 

 seasonal prevalence of these flies [see this Review, Ser. B, iv, p. 195]. 

 H. lineatum oviposits as early as 15th April, though the usual period 

 is during May. Between the last appearance of H. lineatum and the 

 first of H. bovis there is usually an interval of 10 days during which 

 the cattle are immune from attack of either species. It is not yet 

 kno-^Ti how the larvae reach the oesophagus, through which they 

 pass to the submucosa. The earliest record made at Agassiz was on 

 15th August, when larvae 3 "4 mm. long or slightly larger were found. 

 H. lineaium makes its appearance on the backs of cattle about 15th 

 December and H. bovis about a month later. By this time the larvae 

 have grown to about 15 mm. At this stage it becomes difficult to 

 separate the two species. In the latter part of the season (mid- March) 

 the last larvae to leave the gullet are at the paunch end. They pass 

 out under the pleura and go to the neural canal either up the crura 



