SIGHT — FIELDWORK AND EXPERIMENTS 37 



cloth should be draped gently over part of the tank to reduce 

 light. You must have only enough light for you to be able 

 to watch the frogs easily. Having done this, take a chair and 

 sit patiently until the frogs have quietened down. 



Before long, you will see an insect that has attracted the 

 frogs' attention by its own movement. The insect may be 

 well behind the frog's head, but the frog, if hungry, will 

 swivel round — thus showing its angle of vision. If the insect 

 is very near, the frog will then make a grab with open mouth 

 and, more often than not, will catch its victim. As I have 

 just said, an insect may climb up a grass stem some distance 

 from the frog, and if this is seen by the frog a quick jump and 

 open-mouthed attack will result in the insect disappearing 

 almost faster than your own eyes can see what has happened. 

 I once saw a most interesting piece of feeding behaviour in 

 a reptiliary which showed how careful one should be not to 

 accept everything stated in many books, e.g. that our 

 Common Frog cannot climb. 



It so happened that in this reptiliary there were some 

 dwarf trees and shrubs — two to three feet in height. There 

 were plenty of insects about — house flies, small moths and a 

 few cabbage white butterflies. I watched the frogs feeding 

 normally for a while, and then saw that one had been 

 attracted by two butterflies which had first flown into one 

 of the little shrubs and then come to rest. To my eyes it 

 seemed as if these insects were quite still ; but the frog could 

 obviously detect some motion for it moved slowly, more like 

 a toad than a frog, and started to climb into the very lowest 

 branches of the shrub. It did this almost as easily as a tree- 

 frog could do ; it moved higher until it was about eighteen 

 inches or so from the ground. It then waited for a moment 

 of two when it must have perceived some small movement 

 on the part of the butterfly. The frog tensed and then 

 launched itself about a foot forwards and upwards and 

 caught the butterfly with ease. The force of its leap made the 

 frog lose its balance and down it tumbled to the ground. 

 It was quite unhurt but looked rather ridiculous with the 

 tips of the butterfly's wings sticking out on each side of its 

 mouth ! There was a slight pause, a gulp and the meal was 

 finished. 



