BEES IN COLONIES AFEECTIOD BY EUROPEAN FOULBROOD 7 



glistening character and a slight tinge of grayish or creamy dis- 

 coloration which would not be noticed except in direct sunlight. 

 These larvae showed only Bacillus jjluton present when examined 

 microscopically, as will be mentioned later. Soon after these first 

 symptoms, however, the more noticeable symptoms appeared, such 

 as a larva with its back out, the increase of the light grayish yellow 

 color, and, later, the moist, melting appearance. 



A statistical record was kept of the number of larvae showing new 

 disease at each observation, the number previously diseased that had 

 been cleaned out in the interval since the previous observation, and 

 those remaining over in the cells uncleaned for more than one period 

 between observations. At various times observations were made of 

 the behavior and types of bees engaged in cleaning up and the fate 

 of the material removed. Great care was necessary in these obser- 

 vations to disturb the colony as little as possible. On good days 

 it was sometimes possible to remove a comb carefully from the hive 

 and to watch the bees continuing at their work, and even to watch 

 the queen laying eggs. An eight-frame observation hive containing 

 a strong healthy colony was given a diseased comb from time to time 

 and the bees were observed as they worked on it. 



One of the difficulties of the work was to find a satisfactory method 

 of recording the desired data for each comb. At first the diseased 

 cells were marked on the comb by a circle of red celloidin around the 

 entrance of the cell. Although this dried rapidly, it proved unsatis- 

 factory, as the bees, in their attempt to remove the foreign material, 

 seemed to. remove both diseased and healthy larvae indiscriminately. 

 Next small pins were used, inserted in the cell above the one showing 

 disease. In this case the bees tore down the surrounding cells and 

 completely removed the pins, many of which were found on the 

 bottom board. Finally a method of plotting the diseased cells in a 

 comb was adopted. An empty frame was laid off in inch squares by 

 means of heavy black thread. This, used as a templet superimposed 

 on a comb, aided in the location of the diseased and cleaned out cells, 

 so that they could be recorded on a correspondingly ruled card (fig. 1) . 

 Placing this over the comb, it was easy to locate exactly each cell and 

 to determine how long the diseased material remained, thus aiding 

 in following the course of the disease throughout its various stages. 

 The only difficulty with this method was the tediousness of the obser- 

 vations. Therefore, after the disease had become definitely estab- 

 lished, daily observations of each colony were considered unneces- 

 sary. Longer periods showed just as well what was happening in the 

 colony. Also, after the disease had developed enough so that it could 

 be definitely predicted whether the colony would recover or gradually 

 be exterminated; observations of behavior under treatment were 



