148 Annals Entomological Society of America [Vol. XIII, 



tion found in a large number of tree-infesting leafhoppers such 

 as those found in the family Bythoscopidce. 



But a small percentage of the leafhoppers winter in the 

 nymphal stage and when they do it is usually in response to some 

 peculiar adaptation. Dorycephalus platyrhynchus, is a remarkable 

 shovel-nosed leafhopper so wonderfully fitted to the stem of the 

 Elymus (wild rye), that it is even said to show the rust spots so 

 well that the species of rust can be determined. This species 

 shows an equally remarkable adaptation in its life history. The 

 eggs which are laid through a long period of time, hatch out at 

 the time the flowers appear, and the little alligator-like hoppers 

 waddle their way up the stalk to the head and come to rest flat- 

 tened out beneath the glumes where they remain and suck out 

 the nutrition intended for the developing seeds. When the seeds 

 mature they pass to the base of the plant and feed on the green 

 sprouts until winter. In the spring they come out and feed 

 again until May when they change to adults, ten or eleven 

 months from the time they left the egg. It would take a math- 

 ematician of some ability to figure many generations in a season 

 of this species and it would take a mind of equal ingenuity to 

 devise a more interesting adaptation. 



In the old group Tettigonidce the great majority of the species 

 pass the winter in the adult stage and have a single annual gen- 

 eration. Oncometopia lateralis is a typical example of this 

 group. In this we see the adults mating and beginning laying 

 eggs in May, continuing until the end of July. The first eggs 

 develop into adults some time before the last of the overwinter- 

 ing brood of adults disappear so that we have adults the year 

 round and nymphs coming on through a period of three or even 

 four or more months. The writer studied this species in Col- 

 orado and there the adults that develop, whether early or late, 

 do not become sexually mature until the winter has been passed. 

 The continuous occurrence through such a long period of time 

 has frequently led the mathematical investigator astray. 

 Sanderson working in Texas suggested a possible five genera- 

 tions, while Gibson working in Arizona, with what was probably 

 a two brooded species, announced six. 



Turning to the two brooded species of leafhoppers the life 

 history of Empoa rosce, the rose leafhopper, was carefully worked 

 out by Childs in Oregon and shows a beautiful adaptation to the 

 long and even temperature conditions during the growing season 



