PROTOZOA OF LATEX PLANTS 271 



cases in enormous numbers in small laboratory containers and 

 secured free of the infection by being thus hatched from the 

 egg in the absence of older insects, and since it is only necessary 

 to feed such insects on infected plants from greenhouse stocks 

 or cut tops of infected plants from field collections to obtain mate- 

 rial for study, it should be possible to obtain the required informa- 

 tion. 



Information on the length of the incubation period, or time after 

 the first infective feeding preceding the first possible transmis- 

 sion to plant hosts, is needed for all the plant flagellate species. 

 This period must be correlated with the progress of the infection 

 within the insect. 



Specificity for insect Jwsts. It seems probable that more than 

 one insect species can act as vector for a given latex flagellate. 

 Thus Herpetomonas davidi has been reported as carried by 

 StenocepJiahis agilis, Dieuches humilis and Nysms euphorhice as 

 previously stated. The identity of the flagellates in these hosts 

 should be confirmed. In the writer's experiments Oncopeltus fasci-a- 

 tiis has repeatedly transmitted Herpetomonas ehnassiani to seedling 

 host plants in greenhouses in a region where no transmission oc- 

 curs outdoors. Oncopeltus cingulifer (Noguchi, 1924), O. luctuo- 

 siis (Franca, 1921), O. quudrigiittatus (Bancroft, 1928) have been 

 found associated with infected plants of the asclepiadace^. It 

 will be necessary to establish colonies of each insect species, rear 

 nymphs from eggs and infect them from known sources of 

 flagellates, subsequently infecting healthy seedling plants by al- 

 lowing these insects to feed on them, in order to prove that they 

 are capable of acting as transmitters. 



It has been observed that insects of the genus Lygcuus, close 

 relatives of Oncopeltus, can take up the flagellate Herpetomonas 

 elniassiani from infected Asclepias plants, and that the flagellate 

 appears in the feces in twenty-four hours. Infected specimens of 

 Lygceus kalmii were found in the field by Noguchi. But the geo- 

 graphical distribution of the plant infections makes it appear 

 probable that Lygcuus is not associated with the spread of this 

 flagellate. Experimental investigation is needed. A considerable 

 number of species of Lygccus can be obtained. The Catalogue of 

 the Hemiptera of America North of Mexico, University of Cali- 

 fornia Publication in Entomology No. 2, by \'an Duzee, 1919, 

 lists the species native to each locality in the United States. 



