JOIMAL OF AGRIQllTDRAL RESEARCH 



Vol. XVI Washington, D. C, March 3, 191 9 No. 9 



TWO SPECIES OF PEGOMYIA MINING THE LEAVES OF 



DOCK ^- 



By S. W. Frost - 

 Instructor in Entomology, The Pennsylvania State College 



INTRODUCTION 



The life history and habits of two leaf-mining Anthomyids {Pegomyia 

 spp.) are presented in this paper for the first time. The docks Rumex 

 crispus h. and R. obtusifolius L. are extensively mined by several species 

 of Pegomyia. Among these are two ^, P. calyptrata Zett. and P. affinis 

 Stein., which occur commonly throughout the United States. P. calyp- 

 trata Zett., is by far thie more common of the two species. The adult 

 is readily distinguished by a bluish-gray thorax and a reddish-yellow 

 abdomen. P. affinis Stein., on the other hand, is less common. It 

 occurs about Ithaca, N. Y., abundantly in early summer, but later in 

 the season no eggs, larvae, or adults have been found. This species is 

 distinguished by its inconspicuous gray color. 



THE MORE COMMON SPECIES, PEOQMYI A CALYPTRATA 



HISTORICAL REVIEW 



P. calyptrata Zett. was first described by Zetterstedt (1846).^ since 

 that time there have been but few references to it. Stein (1897),^ (1907),^ 

 and Pandelle (1901)'' refer to this species, but mention nothing regarding 

 its habits. This species has undoubtedly been noticed by many, but its 

 identity has been unknown. In looking over some unidentified material 

 in the collection at Cornell University the writer found specimens reared 

 by Prof. Comstock as early as 1882. Dr. A. O. Johannsen, also of Cor- 

 nell, noticed the same species in 191 3 mining dock, but did not publish 

 his observations. 



' Contribution from the Entomological Department of the Cornell University Agricultural Experiment 

 Station. 



2 The writer wishes to acknowledge his indebtedness to Dr. Robert Matheson, of the Department of 

 Entomology, Cornell University, for many helpful suggestions and the criticism of this paper. 



' There are at least two other species of Pegomyia occurring in this country, Pegomyia bicolor Wied. 

 and Pegomyia winthem.i Meig., which mine Rumex spp. These occur in the northern United States and 

 Canada, but do not appear to be common at Ithaca, N. Y. 



* Zetterstedt, J. W. diptera scandinavl/E. v. 5, p. 159 Limdae. 1846. 



5 Stein, P. nordauerikanische anthomyiden ... In Berlin. Ent. Ztschr., Bd. 42 (1897), Heft 3/4 

 p. 239-241, 286. 1898. 



5 Becker, Th., BEza, M., KERTi:sz, K., Stein, P. katalog der palaarktischen dipteren. v. 3, 

 p. 701. Budapest. 1907. 



' PANDB1.1.E, L. ETTJDEs SUR LES MtJSCiDES DE FRANCE. In Rev. Ent. France, t, 20, no. i, p. 294, 

 1901. 



Journal of Agricultural Research, Vol. XVI, No. 9 



Washington, D. C. Mar. 3, 1919 



rl Key No. N. Y. (Cornell^ 



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