10. 



National Bibliothek," No. 3, Jahrg. II., 1911, where it is 

 stated that the botanist Naegeli described the carrier of the 

 pebrine, as early as 1857, as Nosema hombycis. This review, 

 moreover, mentions the fact that W. Stempell (38. Jahresber. 

 Zool. Sekt. Westf., Prov. Ver. f. Wiss. u. Kunst, 1909-10, p. 37) 

 has made artificial infection experiments with this parasite, 

 and found that it develops with extreme rapidity and great 

 virulence, not only in caterpillars of the silkworm, but also 

 in caterpillars of several local species of the same family. Thus 

 Stempell reached the conclusion that this susceptibility of the 

 individuals towards the pebrine parasite might be used prac- 

 tically in combating injurious caterpillars. He further men- 

 tions that his researches on this and other Microsporidia are of 

 biological interest, since it would seem that there must be 

 organisms so minute that they cannot be seen, even with our 

 most modern optical instruments. In several infectious diseases 

 the carriers of the disease have not yet been optically demon- 

 strated, and it may be that these carriers are such smaU 

 organisms. These little oval shining bodies are now no longer 

 regarded as plant organisms, but as belonging to the Psoro- 

 spermii, a group of Protozoa. Pebrine is extremely in- 

 fectious, and is carried over, as Pasteur has proved, from gen- 

 eration to generation in the eggs, with increasing destructive- 

 ness. 



We come now to the last and probably most important of 

 all the common caterpillar diseases, the disease called Flacherie, 

 Flaccidenza or caterpillar cholera, and in America known also 

 under the name " wilt disease." This disease is characterized 

 as follows: a caterpillar suffering from it soon stops eating, 

 becomes weak and lazy, and usually crawls up on some object, 

 as the trunk of a tree, a fence, a wall, or other vertical surface, 

 where it remains without motion. In a few hours there drops 

 from its mouth and anus a dirty, blackish, foul-smelling liquid ; 

 the caterpillar becomes more and more flaccid, one leg after the 

 other looses its support, and finally the creature, reduced to a 

 black skin, hangs dead, still holding on with one or two of its 

 false feet or with the anal claspers. The slightest touch now 

 sufiices to break the skin, and a thin, dark, offensive-smelling 



