160 journal of economic entomology [vol. 9 



Pasteur-Chamberland Filtrate Experiments 

 Since our experiments seem to demonstrate that the wilt virus is 

 capable of passage through Berkefeld candles it was thought impera- 

 tive to ascertain whether or not the virus could be passed through 

 something finer, namely, through Pasteur-Chamberland filters. For 

 this reason the two following experiments (Tables XV and XVI) were 

 performed. The virus was prepared in the usual way and equalled 

 60 c.c. This was passed through a Berkefeld "N" filter (vacuum of 

 27 inches) after which the resulting filtrate was passed through a 

 Pasteur-Chamberland "F" filter (vacuum of 27 inches). Fifth stage 

 foreign caterpillars were used in both experiments and the animals 

 were infected by the pipette method. Tables XV and XVI are self- 

 explanatory. Suffice it to say, that not a single animal died of wilt in 

 either the experiments or checks. These two experiments seem to 

 demonstrate that none of the virus is capable of passage through the 

 Pasteur-Chamberland ''F" filter. In other words, the size of the 

 organism concerned in wilt lies somewhere between the size of the 

 Berkefeld and Pasteur-Chamberland filter pores. Of course, some of 

 the virus may have passed through, but was not sufficient to gain a 

 foothold on account of a natural immunity of the animals. This, 

 however, is pure speculation at present. 



Is There any Relation between Sacbrood and Wilt? 



In 1913 White discovered a disease in bees caused by a filterable 

 virus, which he named Sacbrood for the reason that the dead larvae 

 when removed from their cells have the appearance of a small closed 

 sac. The main difference between Sacbrood and wilt, however, seems 

 to consist in the fact that polyhedral bodies have never been found by 

 White in cases of Sacbrood. Of course, this fact need not exclude the 

 possibility of the identity of the two diseases, for the bee larval tissue 

 reaction towards the disease may be entirely different from the cater- 

 pillar tissue reaction. Polyhedral bodies may not be formed when 

 the virus invades bee larvae although formed when the same virus 

 gains entrance to the caterpillar body. 



Through the kindness of Dr. G. F. White, we obtained some Sac- 

 brood material. At the same time we sent Dr. White some wilt 

 material so that he could perform the reciprocal infection, i. e., infect 

 bee larvae with the wilt virus. None of Dr. White's experimental bee 

 larvae developed Sacbrood or wilt as it is known in caterpillars. Tables 

 XVII and XATII represent two experiments accompanied by controls, 

 in which gipsy moth caterpillars were infected with Sacbrood. As can 

 be seen none of the animals so treated succumbed to wilt. From these 

 experiments performed by us in cooperation with Dr. White, we con- 

 clude that wilt and Sacbrood are two distinct diseases. 



