No. 507] SHORTER ARTICLES AND DISCUSSION 187 



he had never seen the horn flies so abundant as they were the 

 past summer. They literally swarmed around the cattle and 

 since the majority of the stock was dehorned the insects would 

 settle all over the backs and sides of the animals although they 

 were in some cases observed to cluster around the horn bases. 



At Harris's ford, where the collecting parties crossed Running 

 Water, several hundred cattle watered all summer. The lower 

 part of the ford is quite shallow, scarcely attaining a depth of 

 more than a foot; somewhat to the right the water deepened so 

 that the cattle in drinking would be submerged nearly to the 

 middle line of their bodies. At noon the cattle would begin to 

 come to water and would continue coming for some hours on hot 

 days; on cooler days they would delay their coming somewhat; 

 and on rainy days they frequently did not come at all. The 

 following observations were made on hot, bright days as our 

 party was returning to camp from the morning work. Mr. 

 Albert Thomson called my attention to the actions of the fishes 

 and we together made the following observations repeatedly. 



The cattle would almost always enter the stream at the shallow 

 part of the ford and gradually wade up stream, drinking as they 

 went, until they came to the deep place near the fence where 

 the water reached well up on their bellies. The chubs seemed 

 to be unusually numerous at the ford, and we often wondered at 

 the great numbers of the little fishes which we could see in 

 schools in the clear water. Their presence was soon explained. 

 As soon as the cattle entered the stream at the shallow place in 

 the ford the chubs would come out from their cool and shady 

 retreats under the grasses along the sides of the bank and hasten 

 to meet the cattle at the shallows. Often we saw as many as a 

 dozen or more chubs following a single cow. As soon as the 

 water came near the bellies of the animals the chubs would leap 

 out of the water and catch the horn flies from the sides of the 

 cattle. Often we saw them leap as much as half their length out 

 of the water to secure a fly which was high up on the animal's 

 side. These observations were made on several consecutive days, 

 and on the last day but one I was so fortunate as to secure a 

 photograph of a chub in the act of catching a fly from the side 

 of a cow and the photograph is published herewith. 



That the fishes actually learned that the dark spots on the 

 sides of the cattle made good food, there can be no doubt. Just 

 how they first learned it we may not know. The chubs had fur- 



