16 
BULLETIN/ 19, U. 5. DEPARTMENT OP AGEICULTTTEZ. 
The number of days required to complete the stages of the nymph 
were arrived at as a result of rearing 114 nymphs through all of the 
five nvmphal stages from hatching to adult during the season of 1912. 
and the data given above are based on these rearings. It was observed 
that variations in temperature greatly influenced the length of the 
different stages. It was also noted that although there might be a con- 
siderable variation in the number of days that were required by nymphs 
of the same age to complete any one of the stages, the total number of 
days covered would vary but slightly : since it frequently happened that 
when one stage was protracted beyond the average period, some other 
stage would be considerably shortened, and thus the total number of 
days for the entire nvmphal period would 
be about the same for all nymphs of the 
same age. See Table XL 
SEASONAL HISTORY. 
ACTIVITIES OF ADUTTS IN EARLY SPRING. 
The adult grape leafhoppers become 
active in their hibernating places beneath 
accumulations of leaves, trash, and dried 
grass during the warm days of late winter 
and early spring. During the warm sunny 
hours of such days they rise in swarms 
about one's feet when tramping through the 
leaves and dried grass of woodlands and 
swales which adjoin vineyards which were 
heavily infested during the preceding sea- 
son. Dining these periods of activity they 
feed on the green parts of almost any plant that happens to be growing 
near these places of hibernation. At first the green blades of tufts 
of grass or the leaves of goldenrod or wild strawberry, and a little 
later the unfokling leaves of wild raspberry and blackberry, appear 
inn a favorite part of the menu offered by the woodland growth. 
As the days become warmer the adults extend their night and feed 
upon the tender unfolding leaves of nearly all kinds of shrubs and 
undergrowth. When the new growth of the cultivated grapevine has 
attained a length of a few inches there is a general migration of the 
insect to the vineyards. This migration occurs about the middle 
of May in the vineyards of the Lake Erie Valley, and if the days are 
warm and bright the desertion of the woodland food plants for the 
fuliage of the cultivated grapevine in the course of a few days is quite 
complete. In the spring of 1912 this migration from woodlands com- 
menced about May 20. On May 24 the leafhoppers were extremely 
scarce in woodland pkees. where until four or five days previous : 
had been present in swarms since the time of first activity in spring. 
Fig. 12. — Anal segments of male grape 
Ir-v.:"i::rr er a~ i ir~.-j.Ls: z. xzL~i seg- 
ments; 6, genital nooks; c, superior 
clasper: d, inferior clasper. Greatly 
