A SYMBIOTIC FUNGUS OCCURRING I> THE FAT- 

 BODY OF PULVINARIA INNUMERABILIS RATH. 1 



CHARLES T. BRUES AND RUDOLF W. GLASER. 



During the late winter and spring of 1920 the present writers 

 became interested in the supposedly symbiotic organisms which 

 occur in various scale insects, hoping that they might be able to 

 propagate some of them in artificial cultures and learn something 

 of their physiological activities. From knowledge gained thus, 

 it seemed probable that they might be able better to determine 

 whether such organisms exist in the insects as true symbionts, 

 as mere commensals or as innocuous parasites. 



As is well known through the investigations of several workers, 

 the entrance of the symbionts 2 into the egg of scale insects can be 

 readily followed as well as their behavior during embryological 

 development. A good account of this has been given by Shinji 

 ('19) who also includes a summary of the previous work of other 

 authors. 



In the nymphal or full-grown scales of many species it is more 

 difficult to find and interpret the symbionts and it seems probable 

 that in some cases they must either become very much reduced in 

 numbers, very highly modified, or perhaps reduced to minute and 

 unrecognizable spores or granules. 



Several workers who have recently examined the symbionts of 

 Coccids (e.g., Buchner '12, Sulk '10, Teodoro '18) regard them 

 as yeasts (Saccharomycetes), although Berlese ('06) referred one 

 species to the genus Oospora, one of the Hyphomycetes. 



Before beginning our work with Pulvinaria innumerabilis, the 

 cottony maple scale, we examined several other species of Coccids, 

 but were unable successfully to cultivate the symbionts from 

 these, with the possible exception of one of the pine scales, 



1 Contribution from the Entomological Laboratory of tht Bussey Institu- 

 tion, Harvard University, No. 176. 



2 We have used this name as a convenient designation already in current 

 use and will discuss its appropriateness on a later page. 



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