110 DDT — Killer of Killers 



creatures? And when one section of mankind fights another 

 in our periodic wars, doesn't each nation maintain that God 

 is on its side? But what we meant to talk about was cows. 



Insects attack us; but they also attack other animals. 

 Ordinarily this would not interest us in the least, but where 

 the cow is concerned we do take a personal interest. Our 

 interest, of course, is entirely selfish. The mere fact that 

 cows might suffer from fly bites is not, in itself, sufficient rea- 

 son for us to kill the flies that attack the cows. But we get 

 milk from cows, and — at least so we have been told — a cow 

 must be contented if she is to give large quantities of whole- 

 some milk. 



It is very fitting, therefore, that the Walker-Gordon 

 Farms — where they specialize in contented cows — should 

 have been one of the first dairies to use DDT on a large scale 

 to cut down the fly population. Results were very gratify- 

 ing: the fly population was cut to almost zero and, we pre- 

 sume, the cows in appreciation of their increased contentment 

 reciprocated by increasing their yield of milk. 



In the few years since DDT first became available, 

 thousands of dairy barns have been treated with no damage 

 to the livestock but with a great improvement in Bossy's life 

 and with more milk for the farmer. Reports indicate that 

 cows pestered with flies giye 3 to 8 % less milk than their fly- 

 free sisters. 



There are three species of flies that annoy cattle — the 

 housefly, the stable fly, and the horn fly. Of these, the house- 

 fly is the greatest nuisance because it is usually present in the 

 greatest numbers, although swarms of the much smaller 

 horn fly are often found on livestock. Unlike the housefly, 

 which feeds on the body secretions of animals, the stable fly 

 and the horn fly feed upon the blood of animals. The house- 



