28 BULLETIN 805^ U. S. DEPARTMENT OF AGEICULTURE. 



SUMMARY OF SEASONAL HISTORY. 



There are two generations of the rose leafhopper annually at West 

 Chester, Pa. This insect hibernates in the egg stage, the eggs being 

 deposited under the bark of the host plants. On apple stock in the 

 nursery the winter eggs hatch from May 1 to May 15, and the newly 

 hatched nymphs immediately attack the lower leaves of the trees. 

 The feeding period of the first brood of nymphs covers approximately 

 one month. The first adults of the season appear by the end of May. 

 The latter feed for several weeks before mating and depositing the 

 second brood of eggs in the foliage. The length of the life of the 

 first-brood adults is about two months, most of them having dis- 

 appeared by the first week in August. 



The length of the incubation period of the second-brood eggs is 

 about 25 days, the first eggs hatching about July 20. Due to the 

 higher temperatures, the length of the nymphal period of this brood 

 is comparatively shorter than that of the spring brood of nymphs. 

 Second-brood nymphs, on an average, attain the adult stage in 17 

 days. By the latter part of August, practically all the nymphs 

 have transformed to adults. The adults feed for about a month 

 before mating, which takes place during the latter part of September. 

 Females deposit the winter eggs throughout the month of October, 

 soon after which they die. The last adults of the season were found 

 on the trees on November 25. 



NATURAL ENEMIES. 



The most efficient enemies of the rose leafhopper are two species 

 of hymenopterous egg parasites belonging to the superfamily Proc- 

 totrypoidea, Thesepar asites were determined by Mr. A. A, Girault, 

 of the Bureau of Entomology, as Anagrus epos Girault and Anagrus 

 armatus Ashm. var. nigriventris Girault. (See PL V, E.) These two 

 parasites were reared from the winter eggs only, and they emerged both 

 in the fall and in the spring. In the fall they emerged from October 

 15 to November 1, while in the spring they were reared in abundance 

 about one or two weeks after the hatching of the winter eggs. 



These egg parasites are a valuable factor in reducing the destructive 

 numbers of the leafhopper. At West Chester, Pa., from 65 to 70 per 

 cent of the winter eggs were parasitized during 1916. Both of these 

 species evidently are widely distributed, as they have been reared 

 from the eggs in apple twigs from Hagerstown, Md., Winchester, 

 Va., and Roswell, N. Mex. 



Adults of this leafhopper are parasitized quite heavily by a species 

 of the famUy Dryinidae. A rose leafhopper parasitized by a dryinid 

 (PI. V, D) *is readily recognized by the distorted appearance of one 

 of its wings under which the parasitic larva is noticed protruding 



