Longevity, or life histories, of leafhopper species on virus-infected and on healthy plants

does not appear. First page follows. Introduction In discussing the effect of the virus on the insect vector, (Leach (1940))3 has suggested that the question of whether a virus-infected plant is a more favorable host plant than a healthy plant, has been given little attention in virus studies. (Carter (1939)), working with yellow-spot of pineapple, found that infected weeds of Emilia sonchifolia DC maintain, on an average, higher populations of onion thrips, Thrips tabaci Lind., than do healthy plants. He concluded that diseased plants may persist for a longer time, with a mass of curled leaves affording satisfactory shelter for the vector, than do healthy plants which grow rapidly, mature, and die. It is a well-known fact among entomologists who have carried on field investigations with the beet leafhopper, Eutettix tenellus (Baker), that when sugar beets are harvested, the adults fly to other food plants, and a high mortality occurs with the change in host plants. During the 1925 outbreak of the pest, and after the beet tops became dry, enormous numbers of leafhoppers were found in bean fields (Severin and Henderson, 1928), and dead adults were commonly found with their mouth parts inserted in the bean leaves. Tomato plants are favorable host plants of the curly-top virus, but are unfavorable food plants of the beet leafhopper. The decrease in longevity of the males and females on tomato plants has been discussed in a previous paper (Severin, 1928).