Vol. XLIX November, 1925 No. 5 



BIOLOGICAL BULLETIN 



THE RELATION OF HERPETOMONAS ELMASSIANI 



(MIGONE) TO ITS PLANT AND 



INSECT HOSTS. 



FRANCIS O. HOLMES.i 



Herpetomonas elmassiani (Migone) is at present the only species 

 of latex-inhabiting herpetomonad known in the United States. 

 Its plant host is the common milkweed, Asclepias syriaca L., in 

 the latex of which it has been found in great numbers in Maryland 

 and New Jersey (Holmes, 1924, 19250). Its suspected insect 

 host in these locations is a red and black hemipterous insect, 

 Oncopeltus fasciatus (Dall.). The same species of plant flagellate 

 appears to inhabit other milkweeds in countries along the Atlantic 

 coast of Central and South America. It has been reported from 

 Haiti, Honduras and Paraguay, and doubtless exists at inter- 

 mediate points between these countries and the locations in the 

 United States. In southern locations other species of Oncopeltus 

 frequenting the infected plants have seemed to act as insect hosts. 



In view of the lack of apparent pathogenicity of the herpeto- 

 monads in Maryland milkweeds (Holmes, 19256), it seems 

 desirable to report upon the relation of the flagellate to the 

 tissues of its hosts. The well known species, Herpetomonas 

 davidi (Lafont), which inhabits the latex cells of Euphorbias in 

 Europe and elsewhere, is pathogenic to its host (Franca, 1914, 

 Nieschulz, 1922), in which it causes modifications of the latex 

 cells and neighboring portions of the plant sufficient to stunt or 

 kill whole branches or even whole plants. The reasons for the 

 lack of harm resulting in the milkweed host from the presence 

 of Herpetomonas elmassiani (Migone) may be the freedom from 

 infection of some of the latex systems even of heavily infected 



1 Joint contribution from the laboratories of the Boyce Thompson Institute for 

 Plant Research and of the Department of Medical Zoology, School of Hygiene and 

 Public Health, Johns Hopkins University. 



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