38 Journal of Agricultural Research voi. xiii. No. i 



In 1 91 5 the stoneflies appeared early in March, becoming common by 

 the middle of the month. They were observed flying about on warm days, 

 and examinations of the various fruit trees showed that the flies were 

 resting on the twdgs and branches in some numbers. In 1916 the flies 

 did not appear until March 22, as the season was late, but on this date, 

 which was the first warm spring day, they were very numerous. At this 

 time most of the fruit buds were beginning to swell. The flies were 

 abundant during both seasons for three or four weeks, after which they 

 disappeared. The distribution of the species is not well known. The 

 type specimens came from Pullman, Wash., which is 160 miles southeast 

 of Wenatchee, and it is probable that this insect occurs throughout the 

 arid region of the Northwest, wherever there are streams of sufficient size 

 for the nymphs. 



HABITS 



The economic importance of this stonefly lies in its habit of eating the 

 foliage and of biting into the buds of fruit trees. When the flies first 

 appear the fruit buds are beginning to push out, and the flies eat large 

 holes in them, frequently destroying them entirely (Pi. 2, B). Even 

 where the injury is not so severe the blossoms and leaves developing from 

 these buds are deformed and ragged (PI. 2, A). The ovary of the blossom 

 is very often injured, resulting in deformed fruit. Later the insects feed 

 on the calyces and corollas of the blossoms, on the young fruit (PI. 3, B), 

 and on the tender foliage (PI. 3, A,). Apricots, peaches, and plums are 

 most seriously injured. Their buds are soft and tender, and the stoneflies 

 have no difficulty in feeding on them. Cherries are not so noticeably 

 injured, the buds being harder and the young foliage being sticky. The 

 damage to apples and pears is negligible, as their buds are tougher 

 and they blossom later. 



The insects may be found commonly lying lengthwise along the twigs 

 (PI. 2, C), and sometimes on the larger branches. Frequently, by 

 jarring the branches, hundreds of them will be dislodged, and they 

 will drop to the ground or fly awkwardly to other trees. They do not 

 appear to feed when the weat her is cold or cloudy, but during the warmer 

 parts of sunny spring days they are quite actively moving about and 

 feeding on the buds or young foliage. Often they will be found with 

 their heads half buried in the holes they have eaten in the buds, their 

 long, filamentous antennae waving continually. If slightly disturbed, 

 they will stop feeding and remain motionless, or slide around to the other 

 side of the twig. Both sexes have been found in the trees, and mating 

 has been observed to take place here. It is evident that this habit of 

 feeding in fruit trees is an acquired one, since the early stages of the 

 insect are passed in the natural streams, and it was undoubtedly abun- 

 dant before fruit trees were ever planted in the valley. The native 

 vegetation, especially that along the streams, was carefully examined, 



