79 



TVIooRE (W.). Fumigation of Animals to destroy their external 

 Parasites.— J/. Econ. Entom., Concord, ix, no. 1, February 1916, 



pp. 71-80, 2 figs. 



During 1915 a number of essential oils were tested at the Minnesota 

 Experiment Station in relation to their values as insect repellents. 

 Most of the oils were found to injure plants and when placed on animals 

 afforded only temporary relief. The benzene series of compounds 

 was also tested. A rat placed in a fumigation box having a capacity 

 of 180 cubic feet and the atmosphere saturated with nitrobenzene 

 was active and feeding at the end of 24 hours ; after 36 hours, it was 

 alive, but sluggish, and died at the end of 48 hours. The experiment 

 was not conclusive, as the rat was forced to eat food saturated with 

 nitrobenzene, and lack of oxygen may have affected the results. The 

 effect of this compound on insect parasites was observed. Dog fleas 

 were found to leave the host at the end of half an hour and to be quite 

 dead at the end of 1| hours, while the dog itself was uninjured. Pigs 

 infested \\dth lice required an exposure of from six to eight hours. 

 A sheep with very close wool was freed from 90 per cent, of the ticks 

 {Melo'phogus ovinus) on it after 12 hours ; those picked up from the 

 floor of the fumigating box revived after 12 to 24 hours, while those 

 left in the wool did not do so. This result is of especial value, as sheep 

 in wool cannot be dipped successfully. The puparia were not killed 

 by fumigation. Mites on chickens were destroyed in from eight to ten 

 hours, and red mites in a chicken house were also killed. Texas cattle 

 fever ticks {Margaropus annulatus), mostly engorged females ready to 

 oviposit, were killed by an exposure for 10 hours. With one exception, 

 none of the animals fumigated showed signs of injury. Cats were able 

 to withstand an exposure of 1| hours, but were killed in 10 or 12 hours. 

 The author and another person remained in a small room fumigated 

 with nitrobenzene for 1| hours, during which time the house-flies were 

 destroyed, while the only effect on the investigators was a slight 

 irritation to the eyes and throat. In some later experiments the com- 

 pound was allowed to evaporate from a cloth, since evaporation by 

 heat gave a super-saturated atmosphere which was Uable to produce 

 poisonous effects. One drop at 83° F. saturated one cubic foot, while 

 ■at 40° F., only one-tenth of a drop was present. 



Paradichlorobenzene was found to be less poisonous than nitro- 

 l)enzene ; dog-fleas were Idlled in 2| hours, while sheep-ticks were 

 apparently unaffected. Ortho-, meta-, and para-cresol were tested, 

 l)ut only orthocresol was able to kill fleas in 1| hours, without injury 

 to the animals. Carbolic acid crystals evaporated by heat produced 

 similar results in 1| hours, and saHcylic aldehyde drove the fleas off 

 the animal in five or ten minutes, but did not kill them for some hours. 



Experiments on a large scale, such as the fumigation of barns, are 

 necessary. The chief difficulty in Minnesota is the low temperature 

 of barns in winter, whereby an insufficient quantity of nitrobenzene 

 is held in the air to produce the required result. 



