13 



In this connection an interesting observation of Hin- 

 man's (1932) should "be mentioned. This worker found 

 viable "bacteria within the eggs of Aedes ae&ypti and 

 other mosquitoes. By "both cultural and microscopic ex- 

 aminations he found cocci, "bacilli, and yeast within the 

 mosquito ova. The most common type of "bacteria found in 

 sections was the coccus, with "bacilli rarely "being en- 

 countered. As Hinman points out, probably only a rela- 

 tively small percentage of eggs actually contain micro- 

 organisms. 



Variation of Entomophytic Bacteria ., It is well known 

 that "bacterial cells may change in shape, size, and 

 structure. Some of these changes are due to changes in 

 environment and are not inherited. In other cases the 

 changes are more stable and are the result of artificial 

 selection, and in still other instances distinct mutation- 

 like changes occur. 



Into which of these categories fall the various in- 

 stances of variation among entomophytic "bacteria is diffi- 

 cult to say. Besides the occurrence of "bacterial varia- 

 tion within the insect host itself, this phenomenon has 

 also "been observed in artificial cultures isolated from 

 the host and in other insects artificially inoculated with 

 the "bacterium concerned. 



As in the early history of "bacteriology, variation of 

 "bacterial species in insects has caused considerable 

 trouble and controversy among investigators. Typical of 

 this is the case of Bacillus alvei, the cause of European 

 fouTbrood of "bees. Cheshire and Cheyne (1885) were the 

 first to isolate this organism as the etidlogic agent of 

 this disease. Maassen (1907) "believed that either 

 Bacillus alvei or Streptococcus apis was the cause. White 

 (1912, 1920a, 1920b) was unable to produce typical Euro- 

 pean foulbrood with Bacillus alvei , Streptococcus apis , 

 or Bacterium ( Achromobacter ) eurydice and concluded that 

 a new species, Bacillus pluton, was the real cause. 

 Burnside (192^) attempted to "bring some order out of this 

 confusion "by suggesting that Bacillus pluton , Streptococcus 

 apis , and Achromobacter eurydice are variants or stages 

 in the life history of Bacillus alvei . He found that 

 " Bacillus alvei is capable of morphological, cultural, and 

 "biological transformation and is also capable of stabili- 

 zation, at least temporarily, as a sporogenic rod, an 

 asporogenic rod resembling Bacterium eurydice , or as a 

 ■coccoid form resembling Bacillus pluton . " 



