DIAGNOSING BEE DISEASES IN THE APIARY 13 



normally be spinning their coecoons (figs. 5, J-L, and 6, D-F) . Com- 

 paratively few larvae die while fully extended (fig. 6, A, B, tf, G, 



Larvae dead of European foulbrood, therefore, are usually coiled 

 on the bottom of the cells but may be irregularly twisted or fully 

 extended. 



COLOR OF THE DEAD BROOD 



Soon after death larvae become dull and grayish or yellowish- 

 white. During decay the color deepens and may become brown or 

 almost black. The tracheae, or breathing tubes, in dead larvae usu- 

 ally show more clearly than in healthy ones (fig. 5, C and F). They 

 appear as radiating white lines in the dead coiled larvae and as nar- 

 row white lines across larvae that die while extended. A white line 

 which crosses the radiating white lines can frequently be seen on the 

 side of dead larvae. The prominence of the tracheae is a valuable 

 symptom of European foulbrood but is not strictly dependable. 



An elongated, dull grayish-white or yellowish-white mass can be 

 seen through the skin along the back of sick and recently dead larvae. 

 This mass is within the chyle stomach and consists of a turbid fluid 

 that contains many bacteria. In healthy larvae, pollen in the stomach 

 can often be seen through the skin along the back (fig. 5, /), but 

 the color is usually of a brighter and deeper shade of yellow than in 

 affected larvae. Dissecting sick or recently dead larvae and examin- 

 ing the contents of the digestive tract helps in making a diagnosis 

 after experience has been gained. 



CHANGES CAUSED BY DECAY AND DRYING 



The appearance of the dead larvae changes gradually during de- 

 cay and drying. The gray and the yellow colors deepen during decay, 

 but the depth of the color in scales varies considerably. Larvae 

 that die before the cells are sealed dry rapidly, and decay is soon 

 stopped; hence these scales are usually light colored. Larvae that 

 die after the cells are sealed usually become dark brown or nearly 

 black. Diagnosis of European foulbrood is more difficult after the 

 dead brood is decayed and dry. 



For a short time after death, larvae can be removed from the cells 

 without tearing the skin. Within a few days the skin and other 

 tissues become soft ; and the larvae settle against the lower wall of 

 the cells, and appear moist, melting, and flattened. At this stage in 

 decay, larvae are somewhat translucent and watery and cannot be re- 

 moved entire. Upon drying they become pasty, sometimes ropy, and 

 finally rubbery, or brittle. Scales of European foulbrood usually do 

 not cling closely to the cell walls and are easy to remove. 



Larvae that die of European foulbrood in sealed cells may become 

 quite ropy and resemble larvae dead of xlmerican foulbrood. Since 

 the bees remove dead brood from open cells first, it sometimes happens 

 after disease ceases to be active that the brood which died in sealed 

 cells is all that remains in the combs. When this happens it may be 

 difficult to tell whether American foulbrood, or European foulbrood, 

 or both of these diseases are present. 



