Mar., 1917] Distribution of Warble Flies in Ohio 175 



Comparison of Sections of the State. — Perhaps there is 

 little justification for dividing the state into four sections and 

 comparing the warble-fly population of each section. The 

 dift'erences in the number of cattle in each section is not exces- 

 sive. Northeastern Ohio returned according to the assessors' 

 1915 report, 414,954 cattle, an average of 17,289 per county. 

 More than 50 per cent of the cattle in this section are dairy 

 cattle, while 17,957 are classed as beef cattle. The total number 

 of cattle in the Northwestern section is 403,140, an average of 

 14,931 per county, of which 213,295 are classed as dairy cows and 

 27,786 as beef cattle. More beef cattle are found in the North- 

 western section than in any other section, while more dairy 

 cattle are raised in the Northeastern section of the state. 

 The Southwestern section returned a total of 296,000 cattle, an 

 average of 14,800 per county, of which 155,166 are dairy cows, 

 20,147 beef cattle, and 120,722 other cattle. In the South- 

 eastern section 252,668 cattle were found, an average of 14,862 

 per county, of which 108,659 w^ere dairy and 11,422 were beef 

 cattle. 



As has been shown, the warble fly population, based upon 

 the reports and specimens, is greater for Northeastern Ohio, 

 with Northwestern Ohio a close second. However, a more 

 intensive survey would need be made before drawing any 

 general conclusions. One striking feature brought out by a 

 study of the data is shown in the map, page 171. There 

 appears to be a greater per cent of free herds in Northwestern 

 Ohio than in any other section, especially is this true of the 

 Northwestern tier of counties. At present there is no suitable 

 way of accounting for this, as other factors as well as good care 

 must be at work. Dr. Sheets, of Van Wert county, reports that 

 as a general rule, native cattle are free, only imported cattle 

 being infested. Some stockmen report that they never have 

 had grubs in their cattle, while others state that their cattle 

 have had grubs in the past, but are now free, due to a systematic 

 campaign of squeezing them out. 



Relative Attractiveness of Young and Old Cattle. — It is a 



common observation among stockmen that 3^oung stock are 

 more heavily infested than older animals. Whether this is 

 due to the selective action of the flies, or whether the young 

 stock are more accessible, or whether there is any very great 



