PROTOZOA OF LATEX PLANTS 273 



The identification of species. In the absence of adequate criteria 

 and careful tests flagellate species may be wrongly or uncertainly 

 identified with the result that the information gained cannot be 

 used by others. It is therefore desirable that the serum tests pre- 

 viously described be used whenever it is necessary to learn whether 

 two strains of flagellates are specifically identical or not, and that 

 sugar fermentation tests be used when it is desired to characterize 

 a new species or refer a recognized one to its proper name. 

 Fortunately flagellates react to these tests in their characteristic 

 manner without reference to the particular host in wliich they 

 have last grown. For this reason it is possible to identify the 

 strain in an insect with a strain of the same species derived 

 from a plant host without performing transmission experiments. 



It is probable that the careful use of such tests on strains of 

 flagellates formerly reported as Herpetomonas davidi will show 

 that more than one species is represented, since it is probable 

 that the extensive geographical range now ascribed to this species 

 contains many species of flagellates to correspond with the numer- 

 ous insect species present. 



Methods of overzvintcring. In the warmer regions of the world 

 infections in plants and in insects continue throughout the year. 

 An example of this is given by Migone (1916), who states that 

 Araujia august if olia loses its leaves in winter but retains the 

 flagellates in the latex of the stems and twigs. In cooler regions 

 both hosts have long rest periods during the winter months. It 

 is of great practical importance to know how the flagellates pass 

 the cold season. Franca found that Herpetomonas davidi over- 

 winters in the salivary glands of dormant adult insects or large 

 nymphs, and also in the latex of the stems of Euphorbia plants. 



In the case of Herpetomonas elmassiaui in the northern part of 

 its range in the United States the preliminary evidence points to 

 overwintering in the latex in small portions of the basal part of 

 the stem, which alone retains the latex after the death of the 

 stem above ground. Latex cells in this basal portion of the stem 

 may penetrate the new growth the following year. It is desirable 

 that infections be studied before the plants begin growth in the 

 spring. By marking the location of heavy infestations in the fall 

 it may be possible for some worker who has infected plots at hand 

 to work out this problem. The overwintering stage of the insect 

 host, Oncopeltus fasciatus, is not known. 



