KEPOnT OF THE ENTOMOLOGIST. 221 



ON THE PRECAUTIONS NECESSAKT IN TIEE PRODUCTION OF PUEE 

 SLLK-WOEM EGGS, AND IN PROPEELY WINTERING TIIEM. 



For sucli accurate knowledge as we have of the diseases allecting the 

 mulberry silk-worm we are largely indebted to the Freucb savant, Louis 

 Pasteur, who made tliera the subject of exhaustive researches. He 

 found, when he turned his attention to the matter, a long list of maladies 

 whose marks of distinction were anything but clearly drawn. After a 

 careful study of these, however, he writes: " I ought to say that I know 

 but four well-marked diseases among silk-worms. They are the gras- 

 serie, the muscardine, the JfacJieric, and the pcbrine. All others appear 

 to me to be merged in these."* The first two can be easily disposed of, 

 for the grasscrie never appears in the moth and cannot, therefore, affect 

 her eggs. The muscardine, though it may be so slightly developed that 

 the worm is permitted to spin, will invariably destroy the chrysalis, 

 while the disease can never originate at this state, as the insect is pro- 

 tected by its cocoon. The moth, if kept free from larvai afl'ected with 

 the disease, is never afflicted with the muscardine. Her eggs, therefore, 

 cannot contain its spores. But, in the fiachcrie and th.e iiebrine^ we have 

 two diseases so contagious and so destructive that it is necessary to 

 combat them by stringent and thorough measures. 



FLACCIDITY (FLACHERLE). 



Symptoms and Consequences. — Before treating of preventives or reme- 

 dies, however, it will be well to describe the symptoms of the two dis- 

 eases and the means of detecting them, so that the measures which it 

 is necessary to take in order to obtain eggs free from their influence, 

 may be better understood. When, after the worms have passed their 

 fourth molt, and are eating well and regularly, they have all the appear- 

 ance of perfect health and vigor and the silk-raiser feels full confidence 

 in the success of his crop, some will often be seen to crawl to the edges 

 of the trays, and lie there languid and without motion. But for the 

 loss of their wonted activity and the cessation of their naturally vora- 

 cious appetite, one would still think the worms in full possession of per- 

 fect health, for they still retain all the outward perfection of form that 

 we have remarked above. In color they have perhaps becoiue some- 

 what more rosy, especially if the disease is in a violent form. On touch- 

 ing them, however, we find them soft, and even in this seemingly 

 live condition they are often dead. Had the worms been carefully ob- 

 served at this time, it would have been seen that the beating of the 

 dorsal vessel was gradually becoming slower, and that it finally stopjKHl 

 altogether; and that the worm was excreting a dirt^' liquid which soiled 

 the anal orifice and gradually closed it. Befor<* many hours are passed 

 the skin begins to shrivel and draw in around the fourth and fifth joints 

 of the body, viz, those two lying between the set bearing the legs proper 

 and the set bearing the prolegs. Later, at this restricted point, the 

 body begins to turn brown, then black, and the whole worm is soon in 

 an advanced state of putrefaction. Then, and even before the death of 

 the worm, a sour odor is perceptible in the magnanerie, due to the fatty 

 volatile acids exuded by the victims to the disease. Should the malady 

 strike the insects at a later period, when they are ready to spin their 

 cocoons, the same languishing air will be observed ; they will show a 

 reluctance to crawl up into the arches, and will be seen to gather around 



*" £tudes Sur la Maladie dcs Vers a Sole,'' vol. i, p. 225. 



