660 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 27 



indistinguishable morphologically from B. plitton. (Plate 6, E.) Many 

 cultures yielded both B. alvei and 6". apis. (Plate 6, F) In some cul- 

 tures the cells of the coccoid form were observed to be dissociated. Oc- 

 casional cultures of B. alvei prepared from sick or dead brood — the rela- 

 tive number varied in different samples of infected brood comb — grew 

 slowly and sporulation was delayed and incomplete. In a few instances 

 rough inoculation from affected brood yielded cultures of rods which 

 did not form spores at all when cultivated at room temperature. Cul- 

 tures of asporogenic rods were also obtained, some of which closely re- 

 sembled B. enrydice, by plating directly from sick larvae at room 

 temperature. 



In a few cultures on bouillon agar or egg-yolk agar prepared with 

 bacteria from the digestive tract of sick larvae no growth was detected. 

 From the same larvae, however, prompt and abundant growth was ob- 

 tained in dilute sterile filtrate prepared from macerated honeybee larvae. 

 In filtrate medium a coccoid organism resembling .S". apis (Plate 6, G) 

 was usually obtained, but some cultures yielded also small or moderate- 

 sized rods. It is evident that failure to obtain growth on ordinary nu- 

 trient agar does not prove the absence of culturable bacteria. 



Cultures from healthy-appearing larvae from different infected colo- 

 nies yielded in a variable percentage of the tubes apparently one or an- 

 other of the same forms obtained in cultures from sick or dead larvae 

 {B. alvei or S. apis). When combs of brood were removed from colonies 

 shortly after infection had subsided and were kept either at room 

 temperature or at 36° C, none of the larvae dying of starvation or 

 chilling were noticeably decayed by B. alvei, even though this organism 

 was found by cultural tests to be present in the digestive tract of more 

 than 90 per cent of them. 



Bacteria Present in Honey from Infected Colonies. — Bacillus 

 alvei was found to be abundant in honey and pollen from the brood 

 chamber of infected colonies. In advanced cases inoculations of nutrient 

 agar with a single loopful of honey (about 0.001 cc) practically always 

 yielded B. alvei, while a few also yielded 5". apis. In early or mild cases 

 part of the cultures prepared with honey or pollen yielded B. alvei. 



Bacteria Found in Colonies with European Foulbrood Not 

 Present in Healthy Colonies. — In striking contracts to the preva- 

 lence of bacteria in larvae from infected colonies is the complete absence 

 of these forms in healthy colonies. The writer has made microscopical 

 examinations of and prepared cultures numbering well into the thousands 

 from larvae dead of American foulbrood, sacbrood, fungus diseases, plant 

 poisoning, and other brood disorders, as well as from healthy larvae. 



