Chap. VI] 



ANIMALS 



to mention orchids. The beauty and 

 scent of many tropical Lepidoptera 

 denote correspondingly developed 

 senses of colour and smell, and the 

 large blue Morphos of South America 

 and the brilliant bird-like Malayan 

 Ornithoptera are very common in 

 their native countries. But some 

 additional characteristics of many 

 tropical Lepidoptera may be con- 

 sidered here. Thus many tropical 

 flowers have enormously long tubes 

 (Fig. 66), at the base of which there 

 is nectar, which can be reached only 

 by moths with a correspondingly 

 long proboscis. The longest struc- 

 tures of this kind are the spur-like 

 pockets of the labellum of Macro- 

 plectrum sesquipedale, Pfitzer, a 

 Madagascar orchid, which are five 

 decimeters long (Fig. 67). Some 

 tropical Rubiaceae cultivated in the 

 botanic garden at Buitenzorg at- 

 tracted my attention by the unusual 

 length of their corolla-tubes (Fig. 

 68) ; moths with a proboscis suffi- 

 ciently long to be able to suck the 

 nectar that is at their bases do not 

 occur in Europe, and possibly not 

 in any part of the north temperate 

 zone. 



Macroplectrum sesquipedale may 

 be one of these species whose very 

 restricted geographical distribution 

 is connected with that of a genus 

 or species of insect that pollinates 

 them. An indubitable case of this 

 nature is exhibited by several North 

 American species of Yucca, which 

 are exclusively pollinated by moths 

 of the genus Pronuba. Thus Yucca 

 filamentosa, which is frequently grown 

 in our gardens but always remains 

 K 2 



Fig. 67. Flowers of 

 Macroplectrum sesqui- 

 pedale, Pfitzer. All 

 the perianth, with the 

 exception of the spur, 

 removed. In the bo- 

 tanic garden, Heidel- 

 berg. Natural size. 



