26 CIRCULAR 3 9 2, U. S. DEPARTMENT OF AGRICULTURE 



wings and held at abnormal angles. Such bees are capable of only 

 feeble fanning with the wings. The abdomen is often distended 

 with feces and may appear shining or greasy. 



APPEARANCE OF THE INTESTINAL TRACT 



The intestinal tract of bees infected by Nosema apis is fre- 

 quently swollen and discolored. When favorable specimens are at 

 hand this symptom can be used for diagnosis in the apiary. If 

 the bees are alive, or have just died, the entire intestinal tract can 

 be removed as follows : Remove the head and hold the thorax with 

 the thumb and forefinger, then grasp the tip of the abdomen with 

 a pair of forceps and pull gently. By this procedure the entire 

 intestinal tract can frequently be withdrawn from the abdomen. 



In healthy bees the long, cylindrical mid-intestine is usually of a 

 brownish-red, yellowish, or grayish-white color. Circular constric- 



Figure 17. — Nosema disease : A, Intestines from healthy bees ; B, Intestines from bees 

 infected with Nosema disease. 



tions show for nearly the entire length of the intestine (fig. 17, A), 

 and the tissues are fairly tough and of a healthy appearance. When 

 Nosema disease is present the mid-intestine swells (fig. IT, B) but 

 finally shrinks to about normal size. Heavily infected intestines are 

 usually of a dull grayish white, and some or all of the circular 

 constrictions disappear (fig. IT, B) . The tissues become soft and 

 watery and are more easily crushed than are the tissues of healthy 

 intestines. The fluid that flows from heavily infected intestines 

 when they are crushed is whiter and more turbid than is the fluid 

 from healthy intestines. After experience has been gained, it is 

 often possible, when favorable specimens can be obtained, to make 

 a diagnosis of Nosema disease in the apiary. There is considerable 

 variation in the appearance of the mid-intestine of healthy as well 

 as infected bees, however, and in many cases, particularly after 

 the bees are dead, a microscopical examination is necessary for a 

 diagnosis of Nosema disease. 



