EARLY EXPERIMENTS OF PLATEAU AND OTHERS. 141 



it will perceive differences not apparent to us. Moreover, Plateau failed 

 to take odor into account, though this is of less importance, and finally, 

 Lubbock has shown that bees and wasps are so controlled by habit that 

 new flowers would attract them less than those to which they were habit- 

 uated. To determine the attraction exerted by color, Forel cut the antennae 

 of 6 individuals of Bombus terrestris at the base and released them. At the 

 end of 5 minutes a male returned and visited 10 flowers of bindweed in 

 succession, each time flying directly to the flower without hesitating a 

 second. It was caught, the antennae examined to confirm their complete 

 absence, and then released, when it made a single circuit in the air and 

 returned immediately to the flowers, to visit them as before. In the case 

 of other bumble-bees the front of the head was cut away as far as the com- 

 pound eyes and the remainder of the lower lip and the entire pharynx 

 removed. Nevertheless, the bees thus mutilated flew actively, saw, and 

 moved their antennae; when released they returned to the flowers, but 

 remained only an instant in each, since they were unable to suck nectar. 

 At the same time several of the bees without antennae came again to the 

 bindweeds, flying from one to the other with more precision if possible 

 than those with the antennae intact. Two days later several of the mutilated 

 bees were again found on the flowers, visiting them with an astonishing 

 rapidity and precision. When the antennae, the front part of the head 

 and the pharynx were removed from males of Bombus pratorum, one of 

 these made a turn and flew directly back to the Veronica it had been visit- 

 ing, seeking vainly to secure nectar from it as well as from the bindweed. 

 A second shortly returned and behaved in the same manner, while the small 

 females thus treated did not come back, apparently because of their greater 

 intelligence. A wasp, Polistes gallicus, treated in the same way, behaved 

 similarly, returning to the mignonette in a fruitless quest. 



Forel noted that the loss of the antennae in these cases seemed to increase 

 instead of decreasing the precision of flight. The insects no longer balanced 

 to the right and left before alighting, but flew in a straight line to the 

 flower and landed immediately, the difference in behavior before and after 

 the removal of the antennae being especially striking in Vespa. All this 

 seems to indicate that the balancing in flight enables these insects to smell 

 certain substances with their antennae, which explains why this movement 

 is more marked with the wasps which smell readily and see less well than 

 with the bees, where the reverse is true. The experiments were regarded 

 as demonstrating clearly that it is the compound eyes alone that direct 

 flies, butterflies, beetles, dragon-flies, bumble-bees, and wasps in their 

 flight. It is by means of these organs alone that these insects distinguish 

 colors on the wing, as well as objects, especially when they are moving, 

 distances, and pathways through the air. Odor can attract certain winged 

 insects in a certain direction, but without eyes they could not find their 

 way. 



Perception of form. — An individual of Vespa germanica was placed by 

 Forel on a circle of white paper 3 cm. wide, spread with honey. After 

 taking its fill, the wasp flew away, but returned at once directly to the 

 white circle and again sipped the honey. The white paper was then re- 



