The Effectiveness of Protective Adaptations in the Hive Bee, illustrated by Experiments on the Feeding Reactions, Habit Formation, and Memory of the Common Toad (Bufo bufo bufo)

1 A series of experiments on the feeding reactions of the common toad are described and discussed. These experiments represent an attempt (1) to furnish reliable experimental proof of the effectiveness of the protective adaptations of hive‐bees in relation to predatory attack by toads; and (2) to throw some light on the feeding reactions, powers of association, and memory in the toad (Bufo bufo bufo). 2 In Experiment I. 34 toads (after a week's fast) were offered hive‐bees, but no other food, twice daily on seven consecutive days. The daily records of acceptance are as follows:–(1) number of bees eaten, 45, 41, 18, 10, 8, 3, 0; (2) number of toads * eating bees, 25, 16, 10, 6, 5, 3, 0. 3 No fewer than ten toads learned to avoid bees entirely after a single trial acceptance; in nine of these cases a single bee was eaten at the toads' first visit to the hive. By the seventh day the slowest individuals had learned the lesson of avoidance. On this day no bee was touched by any of the thirty‐three toads which completed the tests. 4 In Experiment II., which was carried out as a memory test, the trials were repeated, as before, after a fortnight's fast with eighteen toads which had previously learned to avoid bees in Experiment I. Results showed a marked total reduction (1) in the number of toads which accepted bees (from 16 to 9); (2) in the number of bees eaten (from 87 to 36); and (3) an increase in the number of toads refusing bees throughout the respective experiments (from 2 to 9). 5 A comparison of the rate of learning by individual toads in the two experiments respectively, as indicated by the number of trial acceptances necessary to establish complete avoidance, reveals (1) that in no single case is there an increase in the number of bees eaten; (2) that in fifteen out of eighteen toads there is a definite improvement; and (3) that in several cases the improvement is marked (as from 6 to 1, from 7 to 1, from 17 to 6, and from 12 to 5). 6 It is concluded from these facts (1) that acceptance or refusal of hive‐bees depends largely upon the acquired individual experience of the toads; (2) that inexperienced toads readily accept bees as food; (3) that even under starvation conditions these animals learn in a few trials to refuse and to avoid bees entirely, though other insects (mealworms offered as a test‐feed after the experiments) are readily accepted; (4) that the lesson of avoidance, once learned, is wholly or partially remembered for at least a fortnight; and (5) that hive‐bees are highly distasteful to, and in general well‐defended against, predatory attack by toads. 7 The foregoing experimental results strongly support earlier conclusions based upon the examination of stomach‐contents of tree‐frogs*: namely, (1) that these animals exercise discrimination in the choice of food; (2) that they learn by experience in nature to recognize and to avoid unpalatable prey; and (3) that the mental equipment and feeding reactions of Anura are such as to suggest that the animals have played a part with birds and other insectivorous vertebrates in the evolution, through natural selection, of Warning Colours and Mimicry.