INJURIOUS INSECTS OF 1909 AND IQIO. 39 
have July 13th as the date on which the earliest of the second 
brood become adults. Adults of this second brood were reared 
and placed in pot lamp-chimney experiments, in order to get them to 
lay eggs for the third brood. They were placed on apple and box 
elder seedlings. These box elder seedlings had been gathered in 
May and kept in the insectary, and so had a good chance of not 
having had Empoasca eggs deposited in their tissues previous to the 
opening of these experiments. These adults were allowed to 
remain in each experiment for two days, and were then removed. 
In this way it was possible to figure out approximate length of time 
spent in the egg stage at the time of the season during which these 
experiments were conducted. The first of these experiments was 
opened on July 13th, and the first young which appeared in that 
way was found on July 31st. These experiments were continued 
until August 25th, and fully twenty nymphs of the third generation 
were hatched. The length of time spent in the egg stage by these 
nymphs ranged from about seven to about thirteen days, the aver- 
age being about nine and one-half days. Adding twenty-two days 
(the average length of time spent in the nymphal stage) to July 
31st, the time of the appearance of the first young of the third 
generation in these experiments, we get August 22d as the date 
on which the first of the third generation became adults. It seems 
likely (see above), judging from the probable time at which the 
first of the second brood became adults, that in reality the earliest of 
the third brood became adults several days earlier than August 22d, 
probably as early as August 18th at the latest. As winter egg- 
blisters are not found until into September, it seems fair to assume 
that these earliest adults of the third brood do not deposit winter 
eges, but lay eggs for a fourth summer generation instead. The 
further fact that living nymphs were found in all stages, on alfalfa, 
up to nearly the first of November, in the season of 1908, would 
also seem to indicate that there is at least a partial fourth brood of 
E. mali in Minnesota each year, though it must be remembered, of 
course, that development is much slower in the cool weather of 
September and October than during the summer months. 
Summarizing, we may say that there are certainly three, and 
possibly four, broods of E. mali per season in Minnesota. 
Economic Experiments. 
Experiments with the hopperdozer for Empoasca on apple 
nursery stock: 
