208 THE SCENT OF FLOWERS AS A MEANS OF ATTRACTING ANIMALS. 



distance. Since it has been already explained that animals can perceive scents 

 which will not stimulate our olfactory nerves at all, it is not wonderful that bees 

 will fly from a distance to the flowers of Ampelopsis, although they are not able to 

 see these flowers so far away. They smell the flowers of Ampelopsis which are 

 scentless to us at 300 yards, just as we do the flowers of the Vine at the same 

 distance. 



Of the multitude of remarkable observations concerning the power of smell in 

 animals only those interest us here which are connected with the visits of insects to 

 flowers; of these, two deserve special mention. Some years ago the Aroid Dracun- 

 culus Creticus from Cyprus was planted on the edge of a small group of coniferous 

 plants in the Vienna Botanic Gardens. There was no dungheap or decomposing 

 animal matter anywhere in the vicinity, nor was there any trace of carrion-flies or 

 beetles. But when during the summer the large cornet-shaped flower-sheath of 

 this Aroid opened, innumerable carrion-flies and dung-beetles flew thither at once 

 from all sides. The indoloid scent emanating from the flower-sheath was only 

 noticeable by human beings a few yards off', but the animals named must have 

 smelt it many hundred yards away. In a certain part of this same garden there 

 is a plant of Honeysuckle (Lonicera Caprifolium), and in summer when twilight 

 falls this is regularly visited by the Convolvulus Hawk-moth (Sphinx Convolvuli). 

 These hawk-moths are accustomed, after they have sucked the honey and when 

 the twilight fades into night, to settle near the plant on the bark of old tree- 

 trunks or on fallen leaves, and there they remain with folded wings as if they 

 were benumbed until the next evening. A few summers ago I very carefully 

 picked up one of the pieces of wood which had been chosen as a resting-place by 

 one of these hawk-moths. I marked the moth slightly with cinnabar and brought 

 it, together with the piece of wood on which it remained immovable, to another 

 part of the gardens 300 yards away from the Honeysuckle. When twilight fell 

 the hawk-moth began to wave the feelers which serve it as olfactory organs hither 

 and thither a few times, then stretched its wings and flew like an arrow through 

 the garden towards the Honeysuckle. Shortly after I met the hawk-moth with 

 the cinnabar mark hovering over these flowers and sucking the honey. It had 

 flown straight to the plant, and must have been able to smell the scent of the 

 flowers even at so great a distance. 



One of the most remarkable correlations between flower scent and animals is 

 the development of the scent simultaneously with the time of flying of certain 

 insects. The flowers of certain species of Honeysuckle, which are much visited by 

 crepuscular Lepidoptera (Lonicera Caprifolium, Periclymenum, Etrusca, grata, 

 &c.), of Petunias (Petunia violacea, viscosa, &c.), of Habenaria bifolia, and of 

 many other plants, smell very faintly or not at all through the day. After sunset, 

 from about 6 or 7 in the evening until midnight, they give off an abundant odour. 

 Still stranger is the behaviour of the flowers of Hesperis tristis, of the dark- 

 flowered Pelargoniums (Pelargonium triste, atrum y &c.), and of numerous Caryo- 

 phyllaceous plants (Silene longiflora, nutans, viridiflora, &c.), which are visited by 



