74 THE ENTOMOLOGIST. 



and for these reasons it is the disease which most affects us. 

 Flacherie is most fatal just as larvae are arriving at maturity. 

 The larvae have apparently fed up well, and although there have 

 been a few deaths they have not been sufficiently numerous to 

 cause serious alarm and have been attributed generally to 

 diarrhoea. When nearly full fed, and in appearance healthy, 

 they are so feeble that their movements are scarcely perceptible ; 

 they stretch themselves out on their food-plant or on the top or 

 sides of the rearing-cage, and remain without moving till they 

 die, frequently hanging down supported only by some of their 

 claspers. In these positions they sooner or later become flaccid, 

 sometimes this takes place in a very short time, and they putrefy 

 and turn black in twenty-four hours, the skins being filled by 

 decomposing fluid — being "moist unpleasant bodies," as Mr. 

 Mantalini would have remarked. It is said that, if a silkworm 

 rearing-house {magnanerie) is entered when the worms are dying of 

 Jlacherie, a sour disagreeable odour is perceptible, due to volatile 

 fatty acids formed by the fermentation of the matter contained 

 in the intestinal canals, and which is given off by the worms. 

 Death is due to the derangement of the digestive functions 

 supervening on the fermentation above mentioned ; and it would 

 appear that the disease may be communicated to healthy larvae 

 by soiling their food with the fermenting matter from the 

 intestinal canal. 



Flacherie is due to overcrowding of larvae, to undue moisture 

 in the atmosphere, to too- succulent food or to food given when 

 very damp, or to defective aeration of the breeding-cages. Some 

 of these causes may develop fatal effects within twenty-four 

 hours ; others simply weaken the larvae, and sow • the seeds of 

 disease which will afterwards decimate the brood. Larvae do not 

 urinate, and the large amount of moisture they as a rule take in 

 with their food has in great measure to be got rid of by 

 transpiration ; anything, therefore, which checks this trans- 

 piration is injurious. 



If a few large larvae with their food be placed in a perfectly- 

 closed vessel, they will in a very short space of time be covered 

 by moisture which they have transpired, and which there has 

 been no current of air to carry off. Internal-feeding larvae, even 

 under natural conditions, seem very liable to die of this disease. 

 I have frequently noticed larvae of the genus Sesia dead of it, as 



