204 HALP HOURS WITH INSECTS. [Packard. 



sects which are not capable of fertilizing them. I would 

 venture to suggest, then, that the closing of flowers may 

 have reference to the habits of insects, and it may be ob- 

 served also in support of this that wind-fertilized flowers 

 do not sleep ; and that some of those flowers which attract 

 insects bj' smell, emit their scent at particular hours ; thus 

 Hesperis matronalis and Lychnis vespertina smell in tlie 

 evening, and Orchis hifolia is particularly sweet at night." 



The tongue of the hawk moth is often of great length, 

 adapting it for probing the deep corollas of various orchids, 

 etc. For example, the tongue of the moth of the tobacco 

 worm (Fig. 152; a, caterpillar; 6, chrj'salis with its large 

 tongue case reaching to the middle of the body) is very long, 

 but still moderate in its proportions compared to that of a 

 Madagascar species in which it attains a length of nine and 

 a quarter inches, and as there are said to be orchids with 

 flowers as deep as this, there is evidently a relation of cause 

 and effect between the two facts. Some moths, such as the 

 silk worm moths, have the tongue undeveloped and they are 

 not known to visit flowers. Other modifications in the palpi 

 and legs of insects are correlated with the different methods 

 insects take to collect and bear away pollen and honey. 



It is a significant fact, which has been alluded to by 

 authors, that in the arctic regions many flowers are wanting, 

 which elsewhere are fertilized by insects also absent from 

 circumpolar lands. If plants were introduced they would 

 become extinct, possibly not on account of the severity of 

 the climate, but because there would be no insects to render 

 the flowers fertile and capable of producing seeds. The 

 advent of mauy, if not nearly all the flowering plants in 

 past geological periods undoubtedly went hand in hand with 

 the appearance of insects. Now the bees and moths and 

 butterflies, particularly the bees, are among the most highl}' 

 developed of insects, and were the last to appear in the later 

 geological periods. What a striking exemplification of the 



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