20 TECHXICAL BULLETIX 14 9, V. S. DEPT. OF AGEICTJLTTJEE 



in greater number than were the jjupae. The symptoms of disease in 

 the larvae and pupae are quite similar; consequently no attempt is 

 made to differentiate between them. 



The symptoms manifested by infected brood before death are not 

 readily noticeable. There may be a slight increase or alteration in 

 movement in larvae that become infected before the quiescent period 

 or in pupae that are infected just i^revious to the time for emerging. 

 Ordinarily this passes unobserved, since the extent of the movement 

 of which brood is capable, within the cells of the brood comb, is very 

 limited. During their active period diseased larvae may turn to one 

 side or the other or turn completely over, although this is not a usual 

 occurrence. Both larvae and pupae usually die while in their normal 

 position in the cells. 



It is difficult to determine when death occurs, especially during the 

 quiescent period. There are no changes in the outward appearance 

 of infected brood for a short time before and after death. Larvae or 

 pupae, at an age when they are normally capable of movement, may 

 be assumed to be dead when all movement has ceased. The fact 

 can be determined by examination under a reading glass which mag- 

 nifies four diameters or more, or under a binocular microscope. The 

 skin of living healthy larvae normally presents a moist and' glisten- 

 ing appearance. Movements of the mouth parts and breathing 

 movements are readily noticeable. With death all movements stop, 

 and the skin becomes dry and dull after a few hours. 



After death, before mycelium appears outside the skin, changoe in 

 appearance and texture develop. Firmness increases as a result of 

 the interweaving of mycelium in and about the digestive organs and 

 tissues. The color in this stage changes from the glistening white 

 of the healthy larva to a dull, dry, creamy white. Drying, as indi- 

 cated by wrinkling and shrinking, has already begun. The anterior 

 end of the larva, which usually shows the first indications of drying, 

 may be sharply curved ventrally, bringing the anterior and posterior 

 ends closer together. 



Soon after color changes appear the mycelium breaks through the 

 skin. It appears first in a circle of radiating hyphae near the an- 

 terior extremity and gives to the dead larva the appearance of pos- 

 sessing a collar. Development of mycelium over the surface forms a 

 false skin composed of closely woven hyphae. (PI. 1, C.) The seg- 

 mental markings are retained in this false skin; consequently close 

 observation is necessary to distinguish between this and the true skin. 

 The false skin of mycelium may be removed without injuring the 

 true skin if care is used. 



The development of conidiophores upon the surface of the larva 

 begins at about the time of the maturation of the false skin. They 

 form most abundantly at the anterior and less abundantly at the pos- 

 terior extremities where the mycelium is in direct contact with the 

 air. (PI. 1, C.) When the conidiospores mature, the white color of 

 the false skin is replaced, wherever the dead larvae are not in direct 

 contact with the cell walls, by the color of the spores of the infect- 

 ing organism. (PL 1, C.) 



After the spores are mature changes take place much more slowly. 

 Aging of the spores is accompanied by darkening and a loss of bril- 



