04 LEAVES FROM THE BOOK OF NATURE 



rarely, and often after an interval of long years, small 

 armies re-unite again and turn their steps once more to- 

 wards home. 



Of the lower animals, molluscs and infusoria travel 

 probably in largest numbers ; their hosts are literally 

 countless, and it is well known how they give a peculiar 

 color to large tracts of the ocean. 



The most curious circumstance in the life of insects is 

 their migration. They appear in large flights from un- 

 known regions, in places where they have never been seen 

 before, and continue their course, which nothing can check 

 for a moment. They fly, they jump, they even crawl, for 

 hosts of slow, clumsy caterpillars have been met with in 

 the attempt to cross broad rivers. The more disgusting 

 they are, the more persevering seem their labors to fill 

 the earth. The bed-bug, that most hated, and yet most 

 faithful companion of man in all parts of the globe, was 

 not even known in Europe before the eleventh century, 

 when it first appeared in Strasburg, and then, with the 

 beds of exiled Huguenots, was carried to London. The 

 far more useful silkworm, on the other hand, defies all 

 our care and attention, and will not travel beyond the 

 reach of his beloved friend and only food, the mulberry 

 tree, whose leaf has to be destroyed by a vile caterpillar 

 to be changed into bright, beautiful silk. A native of 

 Asia, this worm also was used in China long before any 

 other nation knew of its existence ; in the sixth century 

 a monk brought the first eggs in his bosom to Constan- 

 tinople, and the emperor, Justinian, at once spread the new 

 branch of industry zealously through Greece. When king 



