COLOURS OF FLOWERS AS A MEANS OF ATTRACTING ANIMALS. 197 



" Queen of the Night " (Cereus nycticalus) is perhaps the most renowned of 



all. When dark-coloured flowers are visited at night by insects, for example, 



those of Hesperis tristis, Pelargoniv/m, triste and atrwm, it is not in consequence 



of the colour but of the scent of the flowers, as will be described later on. Without 



doubt, white is the colour which is not only best seen in the dark, but can be plainly 



distinguished in bright daylight, and it is, as far as we know, not avoided by a 



single flower-visiting animal. Even those animals which have a badly-developed 



sense of colour, and can perhaps only distinguish between light and dark, are able 



to appreciate white, as it is the lightest of all colours. Yellow flowers are eagerly 



visited by animals which collect and eat pollen, perhaps because the pollen is usually 



coloured yellow. Greenish-yellow and brownish-yellow flowers, as, for example, 



those of the Parsley and the Parsnip, of the Aralia and the Ivy, of the Maple and 



the Buckthorn, of the Rue and the Sumach (Petroselinum, Pastinaca,Aralia,Hedera, 



Acer, Rhamnus, Ruta, Rhus), are especially preferred by flies which swarm over 



dungheaps and other refuse (e.g. Lucilia cornicina, Onesia sepulcralis, Sarcophaga 



carnaria, Scatophaga stercoraria). This phenomenon has been explained by the 



similarity of the colours named with those of the dungheap and ofFal generally. 



Dark brown must exercise a specially attractive power over wasps. They fly with 



great haste to brown flowers, especially those whose tint resembles that of decaying 



pears and other fruit, whilst they will pass by colours which are far more noticeable 



to other eyes. Flowers of a pale, fawn-red, and dirty violet colour in conjunction 



with brown, so arranged as to resemble decaying flesh and dead bodies, and such 



flowers as possess by way of additional attraction a smeU of putrefaction, are always 



visited by carrion-flies and dung-beetles in abundance. It might be thought that 



the smell alone would suffice to attract these insects; but it must be otherwise, or 



it is difiicult to see why the various Aristolochias, Stapelias, Rafflesias, and Balano- 



phorese, which smell like carrion, should bear its colours as well as its scent. It is 



not easy to decide how much depends upon the colouring, and how much on the 



scent, and it would be premature to give a definite judgment now. It should be 



noted generally that the opinions just stated should not be accepted as being entirely 



free from doubt. Researches on these points are very difficult, and there are so 



many sources of error that the results may have to undergo many corrections sooner 



or later. But, on the other hand, all that has been said must not be regarded as 



quite worthless. This one thing is quite certain — that some animals will show a 



preference for one colour in a flower, while others will prefer another, and that the 



absence or presence, the signiflcance or prominence of single floral colours is to be 



placed on a parallel with the same phenomena in the Animal Kingdom. 



It is extremely probable also that in many floral regions the predominance of 

 certain floral colours at various seasons of the year is connected with the distribution 

 of animals in time, since the insects which fly about in spring and summer, and in 

 summer and autumn differ from one another. It has been shown graphically by 

 curves for the region of the Baltic flora that in April and May a white colour 

 predominates, and that from the highest point in May the curve of white gradually 



