10 



BULLETIN 431, U. S. DEPARTMENT OF AGRICULTURE. 



ceptible, white line. Sometimes there may be seen a narrow area 

 along the median line of the ventral surface that is more nearly trans- 

 parent than the remaining portion of the surface. This area may 

 extend slightly into the anterior and posterior thirds. It is similar 

 in appearance to the one on the dorsal side, but less distinct. A cross 

 section of this third is slightly elliptical in outline. The middle third 

 passes more or less gradually into the posterior third. The juncture 

 on the ventral surface is indicated by a wide angle formed by the 



ventral surfaces of these two thirds. 

 Posterior third. — In form the pos- 

 terior third (figs. 6 and 4) is an im- 

 perfect cone, the axis of which is 

 directed somewhat upward from 

 the horizontal. This third occupies 

 the bottom portion of the cavity of 

 the cell. Its dorsal surface lies upon 

 the bottom wall, with the extreme 

 caudal end of the larva extending to 

 the roof of the cell (fig. 4). The 

 third is marked off into segments 

 by ridges and furrows similar to, 

 but less regular than, those of the 

 middle third. 



TISSUES OF A HEALTHY LARVA AT THE AGE 

 AT WHICH IT DIES OF SACBROOD. 



Upon removing a larva in the late 

 larval stage and puncturing its body 

 wall lightly, a clear fluid almost 

 water-like in appearance flows out. 

 This fluid consists chiefly of larval 

 blood. By heating it, or by treat- 

 ing it with any one of a number 

 of different reagents, a coagulum is 

 formed in it. Upon rupturing the 

 body wall sufficiently, the tissues of the larva flow out as a semiliquid 

 mass. The more nearly solid portion of the mass appears almost 

 white. This portion is suspended in a thin liquid, chiefly blood of the 

 larva. A microscopic examination shows that the cellular elements 

 of the mass are chiefly fat cells. Many fat globules suspended in the 

 liquid tend to give it a milky appearance. 



SYMPTOMS OF SACBROOD. 



The condition of a colony depends naturally upon the condition of 

 the individual bees of which it is composed. In the matter of diseases 

 in practical apiculture the beekeeper is interested primarily in the 



Fig. 6. — Healthy larva and cell viewed from 

 above and at an angle. (Original.) 



