

Vol. XLV. December, 1923. No. 6. 



BIOLOGICAL BULLETIN 



THE ORIGIN OF THE MYCETOCYTES IN 

 PSEUDOCOCCUS. 



FRANZ SCHRADER, 

 BRYX MAWR COLLEGE, BRYN MA\VR, PA. 



INTRODUCTION. 



Symbiotic fungi or mycetozoa which are to be found in many 

 species of insects, have lately been made the subject of some 

 interesting work chiefly in Germany and Italy. This peculiar 

 association between fungus and insect body seems especially well 

 developed in the Homoptera and there a great variety of special 

 features is to be found in its development. In some cases, among 

 which are the mealy bugs of the genus Pseudococcus, the sym- 

 bionts are lodged in or associated with cells that originate in the 

 insect body the mycetocytes. These cells have a peculiar in- 

 terest in that they are evidently very much specialized and are 

 restricted to a very definite locality in the body of the insect. 

 In all of the Homoptera, the symbionts are transmitted from one 

 generation to the next through the eggs; each of which receives 

 a certain number of the fungi from the mycetome or symbiont 

 mass of the mother. In Pseudococcus, such a transfer to the ova 

 involves a dissociation of the symbionts from the mycetocytes, 

 for the latter do not pass into the eggs. When the infection of the 

 egg is complete, the fungi are therefore found "naked" near the 

 anterior pole and always in the form of a number of spherical 

 clumps or packets, each of which contains a large number of the 

 symbionts. During the development of the embryo, these clumps 

 once more become associated with mycetocytes which arise in 

 some way in the embryo. 



The exact nature of the mycetocytes has received a variety of 

 interpretations. Breest ('14), working on Aspidiotus, a coccid 

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