20 BULLETIN 805, U. S. DEPARTMENT OF AGRICULTURE. 



The third-brood eggs hatch from July 30 until about September 1, 

 the length of the egg stage of this brood being about 9 to 10 days. 

 Third-brood nymphs are found on the foliage from August 1 until 

 about the third week in September, the average length of the entire 

 nymphal period being 18.7 days or approximately the same as that of 

 the first brood. By the middle of August the nymphs begin to 

 transform to adults and by the end of September all the nymphs 

 have disappeared. The third-brood adults remain on the trees until 

 cold weather sets in when they gradually disperse to the hibernating 

 places. 



NATURAL ENEMIES. 



The apple leafhopper is evidently quite free from the attack of 

 parasites. Only one record of parasitism has appeared in the liter- 

 ature, R. L. Webster in 1913 having noted the pupa of an egg parasite 

 which, however, died before reaching maturity. 



A few cases of parasitism of adults by a dryiuid have been seen at 

 West Chester, Pa., but no adults of this parasite were reared success- 

 fully. However, two dryinid females were captured in the field 

 while in the act of ovipositing in the abdomen of nymphs of Empoasca 

 mail. These specimens were determined by Mr. J. C. Crawford, of 

 the United States National Museum, as Aplielopus albopictus Ashm. 



Probably the most effective enemy of this leafhopper is the preda- 

 cious heteropteron TripTileps insidiosus * Say. This small black 

 insect, which is rather comm'on on the foliage duriug midsummer, 

 feeds on the nymphs by thrusting its beak into their soft bodies. It 

 is actually of little importance, however, in reducing the numbers of 

 leafhopper nymphs. 



Spiders and various species of mites have been noted attacking 

 and devouring nymphs on several occasions. In one instance an 

 adidt of the pear-leaf blister-mite was found preying on a first-stage 

 nymph. Ladybeetle larvae also are predacious on nymphs to a 

 small extent. 



R. L. Webster (18) records larvae of aphis lions and a dipteron of 

 the family Empididae as feeding on the nymphs in Iowa. 



As in the case of other species of leafhoppers, both the nymphs and 

 the adults are often caught in spider webs. 



THE ROSE LEAFHOPPER, Empca rosae (Linn.). 



HISTORY. 



The rose leafhopper was originally described by Linnaeus (21, 

 p. 439) in Europe in 1758 as Cicada rosae. Since that time this insect 

 has been placed in several genera by various writers in Europe and 

 North America. It was first listed by Burmeister in 1835 as Typhlo- 

 cyla rosae Linn., and under this name it has been commonlyknown in 



