Specificity of bacterial symbiosis in aphrophorinæ

Summary

Aphrophora alni andA. Salicis each have one bacterium in symbiosis. In smears they are specifically different.A. salide. has a long bacillus ;A. alni, a short and delicate bacterium. These germs produce the pigments of their host insects, the symbiote ofA. Salicis an ochre yellow pigment, like the colour of the insect, that ofA. alni red-brown which is the colour of this species. Morphological and physiological tests have shown that the isolation of the symbiotes has been correct.

Sulc and Buchner have illustrated mysterious yeasts or fungi in symbiosis with these insects. These supposed germs are placed in a new genus, Cicadomyces. Details are given to show how they do not represent living entities. Even the authors themselves have subsequently discarded their earlier nomenclature and have designated these bodies simply as symbiotes, feeling themselves doubtful regarding the real nature of the objects they have illustrated. These are best interpreted as protoplasmic debris or pathological products without any nucleus, but merely with chromatinous residues, without any membrane to resist disintegration and digestion and above all incapable of being cultivated and indicating any evidence with regard to their function. These Cicadomyces show a great contrast to real yeast-like symbiotes which have been also illustrated for comparison.