﻿110 BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTURE 



pears that the mortality of grubs under natural conditions is high, 

 and there is the possibility that with only an occasional grub ma- 

 turing the male and female flies would fail to emerge at the same 

 time and mating would not be possible. In carrying out such a 

 plan it is imperative that an exact knowledge of the seasonal devel- 

 opment of the grubs be obtained in advance, so that the date for be- 

 beginning the work will be known with a fair degree of accuracy. 

 Where both species of Hypoderma occur at least four treatments 

 will be required. The first should be completed some days before 

 the time of maturity of the earliest larvae. All cattle exposed to fly 

 attack should be carefully examined. In the greater part of the 

 United States calves under 6 months old would not be found in- 

 fested, but under certain conditions animals as young as 5 months 

 of age may be infested. 



The experiment carried out by Carpenter and his associates (18) 

 on Clare Island, County Mayo, Ireland, amply demonstrates the 

 possibility of complete eradication of grubs, provided all cattle are 

 systematically treated. 



The fact that a few cases of temporary sickness have resulted in 

 cattle from careless hand extraction should not be allowed in any 

 way to interfere with the work of destroying grubs in the backs of 

 cattle. These cases are comparatively rare and the good accom- 

 plished by grub destruction far outweighs any loss which might be 

 sustained. 



LEGISLATION ON GRUB CONTROL 



A very active interest is being shown in various parts of the world 

 in the matter of grub control. Great Britain has for many years 

 given attention to this problem, but her efforts took on more sys- 

 tematic form recently when the English Ministry of Agriculture in 

 collaboration with the Scottish Board and the Department of Agri- 

 culture for Ireland formed a commission of experts to devise meth- 

 ods of control or eradication of the pest. It seems that there is a 

 very strong sentiment in Great Britain in favor of the passage of 

 laws to bring about the systematic destruction of the grubs. In 

 Switzerland and France similar commissions have been organized 

 recently; Germany (67) has had its commission functioning for 

 several years; and in Denmark {26) a law was passed in 1923 by 

 Parliament, looking toward the destruction of all grubs in cattle 

 during the years 1923 and 1924 with a view to complete eradication 

 throughout the nation. 



This action by the legislative authorities of Denmark, it should be 

 remembered, followed years of individual or community effort 

 against the pest. 



It is doubtful if any legislation on the part of our own country is 

 advisable at present. After there have been large-scale demonstra- 

 tions of what may be accomplished in the direction of grub eradi- 

 cation through well-organized cooperative work, however, appro- 

 priate legislative enactments will no doubt be called for. 



SUMMARY 



Cattle grubs of the genus Hypoderma are abundant throughout 

 the greater part of the United States and southern Canada, and in 



