AND OTHER INJl'RIOUS INSECTS OF I907 AND I908. I9 



tion of the bark around it. The pore, when open, was elHptical, ana 

 always had its long axis parallel with the petiole. The opening was a 

 scant .5 mm. long. The bark was slightly raised in the neighborhood, 

 and of a darker shade as if diseased. The whole thing was barely 

 visible to the naked eye. The enlargement was very slight, and in 

 most of those seen, was on the side of the petiole, neither above nor 

 below, and usually on the half nearest the blade of the leaf. I found 

 a single one which was very small and seemingly imperfect, about 

 half way out the blade on the under side of the midrib. Upon dis- 

 section I was not able to make out anything definitely, but thought I 

 saw traces of some foreign body in the plant tissue. I examined sev- 

 eral buckwheat plants rather thoroughly, and found a couple of similar 

 looking places on the petioles." 



Number of Broods: There are surely two broods of Empoasca 

 mail during the season in Minnesota, and almost certainly three. It 

 is easy to define the first two broods, which are fairly well separated. 

 Allowing forty days for each cycle, which seems a fair estimate from 

 the data we have at hand, and bearing in mind that they first appear 

 about May 25th (1907), or soon after the leaves open, we would 

 have, in round numbers, one hundred and twenty days, to September 

 25th (at about which time adults grew appreciably less in numbers), 

 permitting of three such cycles. 



Field Observations in 1907 : The first appearance of the young 

 leaf hoppers was on May 25th, when Webster found newly hatchea 

 nymphs on leaves of three-year-old apple stock in a nursery at Albert 

 Lea. A thorough search May 20th at this place failed to reveal any 

 of the nymphs, but they were found fairly numerous at this latter 

 date. The leaves of apple stock were less than two inches long at 

 this time, the average length being one inch. It would be safe to 

 say that the young hatch about two weeks after the buds burst. Only 

 one specimen was then found on the two-year-old stock, the majority 

 appearing on the older stock. 



First brood of adult hoppers were first seen outside at Owatonna 

 on June 19th, on apple, elm, maple and boxelder. At this date young 

 hoppers were also found, but only on the apple. Specimens of adults 

 were taken on European birch, cut-leaf birch and plum on June 20th 

 at Owatonna, but no nymphs were found on these trees. On July 

 1st, young (of the second brood possibly) were very common at Owa- 

 tonna, the majority of nymphs being in the second nymphal stage. On 

 July 14th, at Albert Lea, Webster found hoppers very numerous, those 

 in the last nymphal stage by far the most common. All stages were 



