February, '09] JOURNAL of ECONOMIC ENTOMOLOOY 57 



interesting to note that the 1908 observance, as far as total time is 

 concerned, was practically corroborated by the work of 1907, when it 

 was found that the insect spent from nineteen to twenty-five days 

 in nymphal stages, although ]\lr. Webster, in 1907, did not determine 

 the length of time spent in each stage. Inseetary observations in 

 1908 indicate that the adult may live at least fourteen days. Its 

 length of life is probably much longer, for experiments in 1907 indi- 

 cate that it may live more than twice that length of time. There are 

 surely two broods of Empoasca mali during the season in INIinnesota, 

 and almost certainly three. It is easy to define the first two broods, 

 which are fairly well separated. Allowing forty days for each cy- 

 cle, which seems a fair estimate from the data Ave have at hand, and 

 bearing in mind that they first appear about ^lay 25 (1907), or soon 

 after the leaves open, we would have, in round numbers, one hun- 

 dred and twenty days, to September 25 (at about which time adults 

 grew appreciably less in numbers), permitting of three such cycles. 

 This estimate is. necessarily, crude. 



5. Economic Suggestions: Though the leaf hopper is found in 

 abundance on trees in apple orchards, the most and perhaps the 

 only serious results of its work along commercial lines are on nurs- 

 ery stock. As remarked l)y a very large grower in our state, "the 

 trade requires a nursery tree between five and six feet high. This 

 standard could be reached in three years if it were not for the leaf 

 hopper, which so retards the growth of nursery stock that we can- 

 not market a tree until it is four years old." This statement is gen- 

 erally true for Minnesota (though there are years when the hopper 

 is not so numerous and some localities where it is not particularly 

 troublesome). The nursery of the above grower happens to be one 

 of the worst afflicted nurseries in the state in this connection. Since 

 the winter egg is laid on the apple, it would appear that one means 

 of lessening the attack on nursery stock, or at least delaying the at- 

 tack, would be to locate said stock at a distance from apple orchards. 

 Secondly, though this is by no means so feasible, to locate nurseries 

 as far as possible from other growths which serve as food plants dur- 

 ing the summer. This suggestion naturally includes the keeping of 

 nurserj- ground free from grasses and weeds which harbor Empoasca 

 during the summer. If. in connection with this partial isolation of 

 nursery stock, a grower uses Bordeaux frequently (as he might for 

 plant diseases), it would seem that it might act in a measure as a 

 repellent. 



In order to kill a large proportion of the first brood, it is desir- 

 able to collect the adiTlts with some form of hopper dozer, sticky 



