29 



Worms affected with pebrine develop slowly, irregularh% and very 

 unequally. Black spots are the most marked outward characteristics 

 of the disease; the internal signs are oval corpuscles only visible through 

 the microscope. 



Worms healthy born may contract pebrine during life, but this may 

 not prevent their spinning, as the disease does not reach its climax 

 before the chrysalid or moth stage, and in its incipiency the worm is 

 strong enough to spin, though the moth will produce diseased eggs. 

 Hence the necessity of repeating 

 the microscopical examination 

 for each generation of worms. 



Pebrine is not always visible, 

 and when latent induces other 

 diseases. When only one crop of 

 cocoons is made annually, it is 

 comparativel}^ easy to resist 

 pebrine, as the germ of it, outside 

 of an &gg, retains its vitality not 

 longer than seven months. The 

 disease takes thirty days to de- 

 velop; therefore, if worms from 

 pebrinized eggs can be made to 

 spin within twenty-five days after 

 hatching, they may 3deld a fair 

 harvest of cocoons. In any case, 

 however, it is only safe to use 

 pure eggs, as pebrine, even in 

 undeveloped stages, renders the 

 worm more liable to contract all 

 other diseases. 



FLACHERIE, OR FliACCIDITY. 



This is now the most dreaded 

 disease among European silk- 

 worms. In general, worms are 

 struck with it after their fourth 

 molt, when they are mature, or 

 even while spinning (fig. 13). 



Without any apparent cause, they begin to languish, then remain 

 completely still, and shortl}^ die. They blacken after death (fig. 14), 

 and give out a disagreeable odor. Often entire chambers perish in a 

 day. Again, the progress of the disease may be slow, the worms even 

 spinning their cocoons, but, dj'ing in the chr3^salid state, they putrefy 

 and soil the cocoon, thus greatly diminishing the value of the harvest. 

 Flacherie is but another name for indigestion. Pasteur and many 



165 



Fig. 13. — Worms affected with flacherie dying in tlie 

 brush (after Pasteur). 



