ox THK FJ.IGllT OF I'LYING-FISHES. 487 



29. Observations on the Flight o£ E^Iying-Fishes. 

 By E. H. Hankin, M.A., Sc.D., Agra, India*. 



[Received August 4, 1920 : Read October 19, 1920.J 



(Text-figures 1 & 2.) 



A point hitlierto overlooked in the stu<ly of the flight of flying- 

 fishes is that the air is suitahle for their flight to very different 

 degrees on different occasions. In this respect their flight 

 resembles that of soaring birds. This statement may he illns- 

 ti^ated by the following examples. 



1. Flight under loiisuitable atinosj^heric conditions. 



On the 1st June, 1920, at about a quarter of an hour after 

 sunset, the ship on which I was travelling across the Aiubian 

 Sea was disturbing groups of small flying-fishes at the rate of one 

 or two groups per minute. The surface of the sea Avas either 

 glassy or disturbed by ripples too small to be easily visible. 



Each fish, on emerging, jumped out of the water so far that, 

 while the body was supported on the outstretched " wings," the 

 end of the tail was still immersed. This organ was tliereupon 

 wagged vigorously from side to side, as is usual when starting, 

 thus forming a trail of ripples in the water. After proceeding 

 thus for the unusually long distance of four or five metres, the fish 

 raised its tail from the water and began to glide. The length of 

 the glide made by each fish was, at first, about a metre. Within 

 a few minutes a, change was obser\'ed. The fishes of each group 

 disturbed by the ship made shorter and shorter glides, until at 

 length each fish fell into the watei' immediately it ceased to move 

 its tail. 



One fish flapped its wings at starting, bvit made no bettei' glide 

 than the others. 



About half an hour previously, in sunshine, the ship had also 

 been disturbing small flying-fishes, which had flown for such 

 distances as are usual. Just before sunset the first symptoms of 

 lessened suitability of the air for their flight were observed. The 

 fishes began to show lateral instability. It may be noted that 

 both vultures and flying-fishes are more apt to show lateial 

 instability late in the afternoon than at other times of the day. 

 The stage of lateral instability shown by the flying-fishes soon 

 passed off and was replaced by one in which the course of each 

 fish, instead of being a horizontal straight line, was undulating. 

 Each fish showed two or three alternations of gain and loss of 

 height before falling into the water. This condition soon 

 changed to that first described. 



* Comumnicated by C. Tate Rega\, F.R.S., F.Z.S. 



