242 RECEPTION OF FLOWER-SEEKING ANIMALS AT THE FLOWER. 



purple underneath and brilliant white above. By day the lobes are furled, so that 

 their dark inconspicuous sides are shown, nor is there any scent or other attraction; 

 consequently it remains unnoticed by day-flying insects. But in the evening the 

 lobes of the corolla fold back, and the white flowers are now conspicuous, whilst a 

 strong Ylang perfume is given ofl" to attract moths. In Hesperis tnst%s, Pelar- 

 goniwm, atrnm and triste, there is a similar periodic exhalation of perfume, though 

 the inconspicuous petals always remain in one position. But here the scent is the 

 main attraction, and at nightfall numerous moths are attracted by the delicious 



Fig 264 — Capitula of Serratula 



I protected try Ants (Formzca exsecta) from the attacks of a Beetle! 

 iOxythyrea fv/tiesta). 



perfume of Hyacinths which is then apparent. Hesperis is visited by great numbers 

 of Owlet-moths (Noctuse) of the genus Plusia, which transfer the pollen from flower 

 to flower. 



Silene nutans, already so fully described (p. 154), may be regarded as the type 

 of the plants now under consideration. It is additionally interesting in that it 

 possesses a double protection against unbidden guests. By its unattractive character 

 during the daytime it is protected from diurnal flying insects, whilst the sticky 

 secretion on its flowering axis keeps off' crawling animals such as ants. 



So much has been said in this chapter concerning ants as undesirable visitors, 

 and of the means for their exclusion, that this is an appropriate place for a brief 

 account of certain instances in which they are of real service in guarding and 



