CHAP. XI. IN RELATION TO CROSS-FERTILISATION. 421 



surface of the bag. I then gathered a spathe and 

 breathed hard into it ; several flies soon crawled out, 

 and all without exception were dusted with arum pollen. 

 These flies quickly flew away, and I distinctly saw 

 three of them fly to another plant about a yard off; 

 they alighted on the inner or concave surface of the 

 spathe, and suddenly flew down into the flower. I then 

 opened this flower, and although not a single anther 

 had burst, several grains of pollen were lying at the 

 bottom, which must have been brought from another 

 plant by one of these flies or by some other insect. In 

 another flower little flies were crawling about, and I 

 saw them leave pollen on the stigmas. 



I do not know whether Lepidoptera generally keep 

 to the flowers of the same species ; but I once observed 

 many minute moths (I believe Lampronia (Tinea) 

 caWiella) apparently eating the pollen of Mereurialis 

 annua, and they had the whole front of their bodies 

 covered with pollen. I then went to a female plant 

 some yards off, and saw in the course of fifteen minutes 

 three of these moths alight on the stigmas. Lepidoptera 

 are probably often induced to frequent the flowers of the 

 same species, whenever these are provided with a long 

 and narrow nectary, as in this case other insects cannot 

 suck the nectar, which will thus be preserved for those 

 having an elongated proboscis. No doubt the Yucca 

 moth* visits only the flowers whence its name is de- 

 rived, for a most wonderful instinct guides this moth 

 to place pollen on the stigma, so that the ovules may be 

 developed on which the larvae feed. With respect to 

 Coleoptera, I have seen Meligethes covered with pollen 

 flying from flower to flower of the same species ; and 



* Described by Mr. Biley in the 'American Naturalist,' vol. vii. 

 Oct. 1873. 



