THEIR RELATION TO PLANTS 



35 



Exceptions occur always and that of Pronuba in its re- 

 lation to Yucca has been related ; but in general the Lepi- 

 doptera pollenize as a mere incident and with the tongue, 

 while feeding. And this tongue is a really interesting bit 

 of structure. It is coiled like a watch spring when at rest 

 between the mouth feelers, and no one would suspect. its 

 presence or size from an ordinary dried specimen; but 

 when uncoiled it is often as long and sometimes much 

 longer than its bearer, and here 

 again we have that beautiful 

 ringed structure that adapts it- 

 self to so many purposes among 

 the insects. There is no flower 

 so deep that its nectaries are 

 beyond the reach of all insects 

 but there are many flowers so 

 deep that only a single long- 

 tongued species is invited. And 

 therefore we have an abun- 

 dance of species with tongues 

 of less than an inch in length, 

 quite a number that have them 

 from two to four inches and 

 a very few where ten or even 

 twelve inches are attained. 



The butterfly tongue really consists of two separate 

 parts or halves, the modified maxillae, held together 

 by specially developed structures; and the space be- 

 tween them forms the tube through which the liquids 

 are carried into the mouth. Each half contains its 

 own supply of muscles, a large tracheal tube extends 

 to the very end, and there is an excellent supply of 

 nerve-fibres to guide the insect in its operations in the 

 depths of the florets. 



Most of the tongue is bare or set with scanty stiff 



FIG. 10. a, tip of butterfly 

 tongue showing the sensory pits 

 and taste cups ; b, section through 

 tongue showing division into two 

 halves. 



