29 



Worms affected with pe brine develop slowly, irregularly, 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 health}^ 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 II a liAMiil .J^l^SMiMFWU(\h'\[ \. 

 cocoons is made annually, it is 

 comparative!}^ easy to resist 

 pebrine, as the germ of it, outside 

 of an egg, retains its vitalit}^ 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 yield 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, 



FliACHERIE, OR FliACCIDITY. 



This is noAV 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. 12). 



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

 completely still, and shortly die. They blacken after death (fig. 13), 

 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, dying in the chrysalid state, they putrefy 

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

 ilacherie is but another name for indigestion. Pasteur and many 



165 



Fig. 12. — Worms affected with flacherie dying in the 

 brush (after Pasteur). 



