134 



Disease of Bees. 



[JUNE, 



haemocoelic space, is thus occupied, and, furthermore, the 

 distended colon exerts pressure on the large abdominal air sacs 

 of the tracheal system and so interferes greatly with their 

 function. The insect is therefore unable to expand them 

 with sufficient air, which is necessary for flight, and this feature^ 

 coupled with the additional weight in the digestive canal, renders 

 the insect incapable, when badly diseased, of flying about. 

 The movements of the legs are not impeded, but the insect 

 only seems to have energy to crawl about in a lethargic fashion. 

 The fact that it cannot fly is not due to paralysis of the wing- 

 muscles ; diseased bees have been kept under observation and 

 occasionally they have been seen to vibrate their wings actively 

 with a familiar buzzing sound. Moreover, if a diseased bee 

 be held under the thorax lightly with a pair of forceps it will 

 vibrate its wings very rapidly in its efforts to free itself, thus 

 showing that there is no paralysis of the wing muscles. Bees 

 in the last stage of the disease, however, do not seem to have 

 strength to move their wings at all. 



While the hind intestine is thus gorged with pollen, &c, the 

 stomach and the remaining portion of the digestive canal contain 

 very little solid matter of any description. Some amount of a 

 dark-coloured fluid is present very often in the chyle stomach, 

 but it is not distended with it. 



The contents of the rectum and colon are represented in 

 Fig. C. They consist of pollen grains for the most part, together 

 with a variable quantity of a bright yellow substance in amor- 

 phous masses, and a large number of bacteria. There is no 

 individual type of pollen grain common to all the bees examined 

 (the digestive contents have been studied in about 100 examples) 

 but in an individual bee there has always been found one 

 species of pollen in much greater abundance than the others. 

 Thus Fig. C represents the usual types of pollen grains : ound 

 in diseased bees received from Thorley. The grains p i 

 predominate, p 2 are also common, while p 3 are few and far 

 between. By counting the number of grains visible in the field 

 of a Zeiss lens, objective D, and eye-piece 2, it was found on an 

 average that 80 p 1 and 6 or 7 p 2 are present to every single 

 one of p 3. Fig. D represents the usual kinds of pollen seen 

 in the colon of diseased bees, obtained from Great Whitcombe, 

 in which about 60 of a are present to about 7 of b, and 



