4 BULLETIN 809, U. S. DEPARTMENT OF AGRICULTURE. 



the first two days of the pupal period. Such brood, therefore, is 

 in capped cells. A description of a healthy larva at this age is 

 given by the writer in a paper on sacbrood (25) and will be recounted 

 here only briefly. 



A larva (prepupa) (PI. II, D, G; PI. VI, G), at the age at which 

 death from American foulbrood takes place as a rule, lies extended 

 lengthwise in the cell with its dorsal side against the floor. It is 

 motionless with its head in the direction of the mouth of the cell, 

 its extreme anterior end extending nearly to the cap at the angle 

 formed by the cap and the roof. Its posterior third lies upon the 

 bottom of the cell and extends to the roof; its length is approxi- 

 mately that of the cell, being about one-half of an inch; its width 

 is that of the cavity of the cell, about one-fifth of an inch; and its 

 two lateral sides cover about one-half each of the two lateral walls 

 of the cells. The ventral surface of the larva is in general convex 

 from side to side and concave from end to end. Transverse ridges 

 and furrows give a segmented appearance to the body. An empty 

 space of considerable extent occurs between the ventral surface 

 and the roof of the cell (PI. VI, G). 



The color of the larva at this time is almost white with a slight 

 bluish tint. The entire surface is glistening. The body wall is 

 sufficiently resistant to permit the removal of the larva intact if 

 care is exercised. The tissue mass as seen when the body wall is 

 ruptured is semiliquid and nearly white in appearance. Upon 

 microscopic examination it is found to be made up very largely of 

 fat cells, and to be free from bacteria and other microorganisms. 



The change from the larva to the pupa (PI. VI, B), as far as out- 

 ward appearances are concerned, takes place rapidly. Infrequently 

 death from the disease takes place during this short period. At 

 this time the bee (PI. VI, B) has neither the outward form of a larva 

 nor of an adult. This stage of the transformation is recognized by 

 the fact that the head is smaller than that of the complete pupa 

 and the appendages are largely wanting. 



The pupa (PI. IV, A, D) immediately after transformation is 

 similar in form and size to the a4ult bee. It rests with its back 

 against the floor of the cell and with its antennae, proboscis, and 

 legs lying along its ventral surface. The posterior third is more 

 pointed and much smaller than the same third of the larva. It lies 

 upon the bottom of the cell but does not extend to the roof. 



The color of the pupa at the time of its transformation is nearly 

 white with a slightly bluish tint. The first pigment observed is 

 seen in the compound eyes. Pigmentation of other parts of the 

 body follows. When death from American foulbrood takes place, 

 it does so almost invariably before the time that pigmentation of 

 the body other than of the eyes has occurred. The body wall of 



