THE CANADIAN ENTOMOLOGIST 199 



not enclosed in a capsule), like the pines ; but the vast bulk of them possessed 

 ovaries or seed cases. These were arranged in three divisions (1) those with 

 one or both of the outer rings (corolla and calyx) wanting (Apetalous) ; (2) 

 those whose petals were not united to one another ( Polypetalous) ; (3) those 

 whose petals were united, whether altogether or only at the base (Gamopetalous). 

 In the first few weeks of Spring it was easy to keep pace with the pro- 

 cession of flowers and assimilate the principles of the new science at the same 

 time ; but in June and July the different kinds of habitat became so numerous 

 and so crowded that one could not visit them all often enough to exhaust their 

 denizens. However, in the course of two years, I knew nearly all in the neigh- 

 bourhood, and it was only by going to a distance that I could add to my ac- 

 quaintance ; but by a happy provision of Nature, when novelties ran out, the 

 I)leasure of renewing old acquaintance out-beggared the joys of fresh discovery. 



(To be continued.) 



A REVISION OF THE NEARCTIC SPECIES OF THE TACHINID 

 GENUS ERNESTIA R. D. (DIPTERA). 



BY JOHN D. TOTHILL. 

 In Charge of Natural Control Investigations, Entomological Branch, Ottawa. 



While in Washington, D.C., in March, 1921, Dr. Aldrich suggested that a 

 revision of the nearctic species of the genus Erncstia would be a profitable 

 undertaking. The rich collection in the L^. S. National Museum was placed at 

 my disposal, and I had with me some material belonging to the Entomological 

 Branch of the Dominion Department of Agriculture and some CalifornJa 

 material belonging to Mr. E. P. VanDuzee. It was soon found that the male 

 genitalia aft'orded an excellent series of characters for separating out the species, 

 and the revision was consequently based largelv upon a study of males. When 

 the males had been sorted out into sixteen species, it was found that the females 

 could be sorted out into fourteen species. It was not possible in all cases to 

 assign a male and female to each species, and as the male characters are more 

 readily seen than the female ones, it seemed better to base the descriptions of 

 new species upon males. Descriptions of twelve new species have been drawn 

 up and also of such of the existing species that seemed to require a more ample 

 description than has been published. \\"ell known and easily recognizable species 

 have not been redescribed. 



It is a great pleasure to acknowdedge the cordial assistance given me by 

 Dr. J. M. Aldrich, and also to express my sense of appreciation to Mr. Arthur 

 Gibson, the Dominion Entomologist; Dr. L. O. Howard, the Chief of the U. S. 

 Bureau of Entomology; and to Mr. A. F. Burgess of the U. S. Bureau of 

 Entomology, for making the study in Washington possible. Mr. Charles T. 

 Greene has been kind enough to make the drawings for this paper. 



The genus Ernesti.a R.D. 



Erigonc R.D. Myod. 65, 18^0. 



Mcricia RD. Myod. 64, 1830. 



Platychira Rond. Dipt. Ital. Prod. 1859. 



Varichacta Speiser. Berl. ent. Zeit. 1903. 



Panzcria R.D. Mvod.. 69, 1830. 



