THE SCENT OF FLOWERS AS A MEANS OF ATTRACTING ANIMALS. 207 



of insects, by which is meant the preference of certain kinds for certain flowers, 

 the matter is only mentioned here very generally so far as the scents are concerned, 

 and only the main results of these observations are given. 



It may be stated as one of these that the indoloid scents have an attraction 

 for certain flies of the genera Scatophaga, Sarcophaga, Onesia, Lucilia, Pyrellia, 

 Calliphora, Sepsis, and Musca, and for beetles of the genera Aleochara, Dermestes, 

 and Saprinus, which appear on carrion and excrement; indoloid scents remain 

 unnoticed, on the other hand, by butterflies, bees, and humble-bees. Aminoid 

 scents attract large and small beetles, especially Cetonias, and after them 

 Hymenoptera; butterflies, however, are hardly ever allured by them. The scent 

 of honey acts powerfully on bees and humble-bees; also on butterflies, burnet-moths 

 (Zygcena), and on day-flying hawk-moths (e.g. the Humming-bird Hawk-moth, 

 Macroglossa stellatarum), as well as on small beetles; but insects which are 

 attracted by indoloid scents are not affected by the scent of honey. Certain 

 Hymenoptera which, oddly enough, themselves have paraffinoid scents (viz. species 

 of Prosopis), fly to flowers with the same smell. Flowers with the scent of Honey- 

 suckle are frequented by large crepuscular hawk-moths, but this scent has no 

 attraction for beetles. Butterflies will pass over flowers with a Honeysuckle scent 

 without pausing, leading us to think that either the scent is not perceived by them, 

 or that they find it unpleasant. 



Many flower scents, especially the parafiinoids, are less easily perceived at their 

 place of origin than at a little distance, which is explained by supposing that the 

 odorous particles liberated from the flowers are acted on by oxygen or aqueous 

 vapour as they diffuse through the air, and that various molecular changes go on 

 in them. But since our knowledge of the chemical properties of scents is still so 

 imperfect we must beware of suppositions of this kind. The phenomenon is most 

 pronounced in the Lime and in the Vine. As one approaches a Lime-tree in full 

 flower the pleasant scent of its blossom is strongest at a distance of about 30 yards; 

 if one comes into the immediate neighbourhood and smells the flowers on its lower 

 branches, the scent is neither so strong nor so pleasant as it was further off In a 

 journey up the Danube, through the part of the valley called the Wachan, with its 

 Vine-clad slopes, I found the air of the whole valley, even that above the water, so 

 filled with the scent of Vine flowers that it seemed almost impossible they should 

 be so far off. And yet the nearest Vines on the banks were 100 yards above the 

 water, and at least 300 yards from the boat. Afterwards I found when wandering 

 through the vineyards that the smell of the flowers close at hand was much weaker 

 than at a distance, and was forced to the paradoxical opinion that with increasing 

 distance and diffusion over a wider area the scent does not diminish but waxes 

 stronger. 



The fact that man can perceive certain odoriferous substances in the finest state 

 of division and at incredible distances paves the way for explaining the so-called 

 animal perception of scents. We speak of this animal perception when we gather 

 from other signs that an animal is able to smell what we cannot at the same 



