58 EXPERIMENT STATION RECORD. [Vol.43 



Self-recording invention for obtaining continuous weight variations in 

 hives of bees, C. E. Sanborn (Oklahoma Sta. R[)t. 1919, pp. 60, 61, fig. 1).— 

 The author describes an automatic, continuous weighing device which records 

 the weight of u hive of bees or any other stationary object the weight of which 

 may vary with the hipse of time. By the use of this invention the weight of 

 a swarm of bees which may leave the hive and the time of departure, a honey 

 flow or dearth, etc., may be accurately recorded. 



European foulbrood, G. F. White (U. S. Dept. Agr. Bui. 810 (1920), pp. 39, 

 j)ls. i', figs. 6). — This account is similar in nature to those by the author on 

 sacbrood (E. S. R., 36, p. 659), Nosema disease (E. S. R., 41, p. 359), and 

 America foulbrood (E. S. R., 42, p. 857). A brief summary of facts based 

 upon the Investigations reported, together wdth the conclusions drawn by the 

 author, follow : 



" European foulbrood is an infectious brood disease of bees caused by 

 BaciUu.'i pluton. All larvfe, worker, drone, and queen, are susceptible to the 

 disease; adult bees are not. .Man evidently is not susceptible to infection with 

 B. plufon nor are the experimental aniiuals. As far as is known. Insects 

 other than bees are not susceptible. Brood can be infected by feeding the 

 colony a suspension of crushed larvae sick or dead of the disease. This is de- 

 scribed in the present paper as the indirect method. The virus contained in 

 a single larva recently dead of European foulbrood will produce a considerable 

 amount of disease when fed to a colony. The larvae can be infected also by 

 a more direct method. A fraction of a drop of a suspension of the stomach 

 contents of a larva sick of the disease added with a capillary pipette directly 

 to the food surrounding the larva to be inoculated will result in infection. 



" B. pluton gains entrance to the larva by way of the mouth. The growth 

 and multiplication of the parasite take place within the stomach (mid-intes- 

 tine) of the larva and do not, during the life of the larva, get beyond the 

 peritrophic membrance. The tissues, therefore, are not invaded by it. The 

 secondary invaders in European foulbrood, B. alvei, Streptococcus apis. Bac- 

 terium eurydice, and Bacillus orpheus, rai'ely, if ever, invade the tissues until 

 the larva is dead or nearly so. In a few instances in microtome sections rod 

 forms have been encountered in the act of invading the tissues of living larvae. 

 The .species, however, was not determined definitely. The period of incubation 

 is slightly less than 3 days. Brood is susceptible to infection at all seasons of 

 the year. More brood die of the disease during the first half of the brood- 

 rearing season than during the second half. 



" The writer has examined samples of the disease from Canada and the 

 United States. From written reports it seems quite certain that it occurs also 

 at least in Denmark, England, Germany, France, and Switzerland. Occurring 

 as it does in this somewhat wide range of climatic conditions, the presence of 

 the disease in any particular locality can not be attributed entirely to the pre- 

 vailing climatic conditions. The quality of food obtained by the bees does not 

 affect greatly, if at all, the coui'se of the disease in the colony, although the 

 quantity may affect it to a variable extent. Experimental colonies may be 

 inoculated and kept in the apiary without transmitting the disease to others. 

 This fact is of special importance, not only in connection with the technique 

 of making studies on the disease, but also in the control of the malady. 



" The thermal death point of B. pluton suspended in water is approximately 

 63° C. [145.4° F.] maintained for 10 minutes. When suspended in honey 

 B. pluton is destroyed in 10 minutes at approximately 79°. Drying at room 

 or incubator temperature B. pluton remains alive and virulent for approxi- 

 mately one year. When dry, B. pluton resisted the direct rays of the sun 



