ART. 1. NORTH AMERICAN" SAWFLIES ROHWER. 23 



irregularity of emergence and the overlapping of the generations re- 

 duces the value of such observations to the minimum of first appear- 

 ance. Observations made during the years 1916 to 1919 indicate that 

 in the vicinity of Washington, District of Columbia, the parent adults 

 of the first generation of the bristly rose slug appear coincident with 

 the full blooming of the Snowball {Viburnum opulus and V. plica- 

 tum) and the weigela {Diermlla floHda). 



From observations by Mr. Eohwer, made during two seasons on 

 the roses at the Eastern Field Station, from notes sent by correspond- 

 ents, and from field studies by Mr. Rohwer and the author at Falls 

 Church, Virginia, and many other places throughout the range of 

 this species' distribution, it seems fair to conclude that Cladius 

 isomerus will attack all cultivated varieties (and species) of rose. 

 Varieties with a small midrib or forms with hairy leaves, while not 

 immune, are not favorable food plants. The one essential is, however, 

 a midrib of sufficient size to hold the eggs. Preliminary observations 

 indicated that certain varieties seemed to be preferred but more ex- 

 tended study proved that the condition of the leaves was a more im- 

 portant factor. There are a few authentic records of the species living 

 on the common eastern wild rose {Rosa palutris Marsh), but the evi- 

 dence seems to indicate that where cultivated roses are present they 

 are preferred. 



The following list gives the varieties of cultivated roses on which 

 larvae have most frequently been observed. 



Climbers. — Rasa mMltiflora, Dorothy Perkins, Philadelphia Crim- 

 son Rambler, Climbing Baby Rambler. 



Hybrid perpetuals. — Paul Neyron, Conrad F. Meyer, General 

 Jacqueminot, Clio, Camille de Rohan. 



Tea. — Radiance, La Tosca, Killamey, White Killarney, Frau Karl 

 Druschki, Mrs. A. R. Waddell, Stanley, Hadley, Mrs. Aaron Ward, 

 Kaiserin Augusta Victoria, Marquise de Querhoent, Gruss an Teplitz, 

 Laurent Carl. 



PARASITES. 



Two parasites are recorded in literature as having been reared from 

 Cladius isom£ru^. They are : 



Frontina tenthredinidarum Townsend.^^ 



Coelopisthoidea cladiae Gahan.^^ 



Neither of these parasites are, however, sufficiently abundant to be 

 considered as a successful means of control. 



"TotMll, Can. Ent., vol. 45, 1913, p. 73. 

 "Gahan, Can. Ent., vol. 45, 1913, p. 103. 



