CHAPTER XI 

 MICROORGANISMS IN THE EGG 



Blochmann (1888) appears to be the first to have recognized the 

 normal presence of intracelkilar organisms in the eggs and body tissues of 

 insects, although years earlier Leydig, Huxley, Metschnikoff , and others 

 had already noted the presence in the embryos of aphids of what is now 

 known as the "mycetom" in which microorganisms are harbored. These 

 bacteroid bodies, which Blochmann first noted in ants and roaches, were 

 designated by Wheeler (1889) as "Blochmann's bodies." Heymons 

 (1895a) found them in the yolk of Blattella germajiica and Edobia livida, 

 where they form a spherical mass. After revolution, the mass, which 

 also includes yolk cells, is found in the mid-gut. Later the organisms, 

 leaving the yolk cells behind, pass through the wall of the intestine and 

 become lodged in the fat body. 



Microorganisms have been recorded in the embryos of Orthoptera, 

 Homoptera, Heteroptera, Anoplura, Mallophaga, Coleoptera, Diptera, 

 Hymenoptera, and other forms. Opinions as to their character and their 

 significance to the hosts differ greatly. Glaser (1920) states that in the 

 blattids the organisms are motile bacteria, but in some aphids they are 

 undoubtedly yeasts. Glasgow (1914) concluded that the organisms that 

 appeared in the cultures from the eggs of Anasa tristis and that were 

 certainly the same as those isolated from the caeca of the alimentary 

 canal of the adult were bacteria. Recently Hinman (1932) recorded the 

 presence of bacteria in the eggs of mosquitoes. Mansour (1930) like- 

 wise referred to the microorganisms found in the egg of Calandra oryzae 

 as bacteria. He stated (1934), however, that they are not symbiotic in 

 the strict sense of the term but are more properly referred to as "com- 

 mensals." In the case of C. gr anuria as compared with that of C. oryzae 

 he points out the nonimportance of these organisms in the life of their 

 hosts. Brues and Glaser (1921), on the other hand, beheve that in 

 Pulvinaria the production of diastase, protease, and lipase by the organ- 

 isms may serve to benefit the coccids and that therefore the possibility of 

 real symbiosis cannot be excluded. Buchner (1930) and his followers 

 take a similar stand. 



For convenience Glaser (1920) uses the term "symbionts" for these 

 organisms, although he is not convinced that there is true symbiosis. 

 For a similar reason "symbiont" will be used in the following account. 



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