650 MICROBIAL DISEASES OF INSECTS 



tain parts of the country it has caused enormous losses. It is spread 

 over England, Germany, Switzerland and other parts of Europe and 

 has been noted many times during the last decade. 



Symptoms. — The presence of disease can usually be detected in an 

 experimental colony during the week that feeding is begun. The first 

 indication of it may be that only a portion of a larva is seen in a cell, 

 the remaining portion having been removed by the bees. Aside from 

 an observation of this kind, the earliest indication one gets from the 

 macroscopic examination is that sick larvas are found among the un- 

 capped brood. 



Sick larvae manifest certain symptoms during the course of the 

 disease by which its presence can be diagnosed while the larvae are still 

 alive. The length of time that a developing bee is sick of European 

 foul brood is variable. In general, the three days just preceding the 

 time when a larva would ordinarily be capped, is the most favorable 

 period for making a diagnosis from the gross examination alone. 

 Healthy larvae at a certain age when slightly magnified show a 

 peristalsis-like motion of their bodies, but larvae of this same age 

 when sick frequently exhibit a marked peristalsis which can easily be 

 seen with the unaided eye. Diseased larvae may show a yellowish 

 tint or appear transparent instead of the glistening white or bluish 

 white of healthy larvae. 



Another symptom often serves for diagnosis. In a healthy larva a 

 poUeurcolored mass is frequently plainly seen through the transparent 

 area along the dorsal median line. If this intestinal mass appears 

 white or yellowish white, the presence of European foul brood is al- 

 most certain. This may be often more plainly observed if the larva 

 is removed from the cell with forceps. 



European foul brood may be positively diagnosed in living larvae 

 of a favorable age and condition by the following method; Remove the 

 larva to be tested from the cell and place it upon glass, preferably with 

 a dark background; with a dissecting needle in each hand and with 

 their points near together, pierce with both needles so as to tear the 

 body wall crosswise, and continue to separate the two portions of the 

 larva. If the larva is diseased, and one is successful, it will be found 

 that the intestinal content will be stripped from and pulled out of the 

 posterior and blind end of the canal. The intestinal content of healthy 

 living larvae cannot be removed in this way. The force which is ap- 



