THE SILKWORM ITS DISEASES AND IMPERFECTIONS. /I 



There are, however, three diseases which far exceed all others 

 in importance, and which have on different occasions, caused 

 fearful mortality amongst the insects. They are known by French 

 names as Flacherie, Muscardine, and Pcbrine. Flacherie, or fla- 

 querie, is a disagreeable and particularly disappointing disease, as 

 it attacks the caterpillars just before their change into a chrysalis, 

 and very rapidly produces fatal results, thus rendering useless all 

 the expense and trouble that have been incurred in bringing them 

 up to that point. The caterpillar feeds up well, eats a great deal 

 and grows very fat, but when it is nearly full fed and its rearer 

 is beginning to look forward to some reward for his pains, it sud- 

 denly, while still appearing healthy, becomes exceedingly inactive, 

 stretches itself out on its food and remains without moving. It 

 becomes limp and flaccid, and so rapid is the spread of the disease, 

 that in twenty-four hours the contents of its body turn black and 

 putrefy. This disease may be produced by overcrowding, and 

 defective ventilation, by the presence of an undue amount of 

 moisture in the air, or by the use of food which is damp, or too 

 succulent. As soon as any caterpillars are seen to be affected 

 they should be removed, or their putrefying corpses will con- 

 taminate the rest. It is possible for flacherie to become hereditary; 

 or it may be developed suddenly in a brood and kill off numbers 

 of them at once. A silkworm which has died of this disease is 

 called in French a wort-flat. 



Muscardine is a disease of quite a different character. It 

 attacks the caterpillars in all their ages, but is by far the most 

 fatal during the period between the last moult and the formation 

 of the cocoon. It is impossible to detect when the insect becomes 

 smitten by the disease, for, outwardly, it at first appears perfectly 

 healthy, though it may have the germs of the disease within. 

 When about to die, however, it becomes languid, and its dorsal 

 vessel pulsates more feebly. It soon dies, and after a while 

 becomes reddish in colour and perfectly stiff and rigid. About 

 twenty-four hours after this, there suddenly appears a fine white 

 powder covering the body. This disease is either caused, or, at 

 any rate, accompanied, by the development of a minute fungus, 

 called Botrytis Bassiana, in the insect's body, and the white powder 

 above referred to consists of its spores. A somewhat similar 

 disease attacking house flies is probably familiar to every one. 

 Towards the close of autumn we sometimes see the flies dead, 

 though in the attitude of life, and adhering to the window panes, 

 while around them on the glass is a sort of white halo, which 

 consists of the spores of the fungus that has established itself in 

 the body of the fly and spread so much as to penetrate all its 



