H. F. BASSETT. 325 



Wood's Holl from Potentilla canadense, by Miss Cora H. Clarke. 

 They differ greatly in form and size, but I did not think the varia- 

 tions were specific and placed them together in the breeding box. 

 The smallest are round or oval, not larger than the smallest pepper- 

 corn, and contains not more than one or two larval cells ; while the 

 largest are an inch long and one-fourth of an inch in diameter, and 

 involve the whole stem and contain a dozen or more larval cells. 

 Were the insects identical the form of the galls would not suggest 

 any specific difference. When the large galls include a joint of the 

 plant the joint is enlarged with the rest, but auxiliary buds are not 

 affected. In this it differs from D. potentilloe Bass., which affects 

 the buds only and whose galls are monothalamous. 



Cynipideous galls resembling the larger form are occasionally 

 seen on the petioles of strawberry leaves, but I have never been 

 able to rear any flies from them. From these I have bred both 

 sexes, and after many attempts to settle the question of species I am 

 always forced to the conclusion that there are really two species, 

 though I can offer no very strong facts to support it. The large 

 females, which I name D. niger Bass., are: 



Body entirely black and shining. The head is short and broad and finely 

 punctate. The antennae thirteen jointed, the first and second reddish brown, the 

 second very short, the others, including the first, all of moderate and uniform 

 length. Thorax smooth, shining. Parapsidal grooves very deep and distinct. 

 No other lines on the thorax. The mesothorax bounded posteriorly by a sharp 

 transverse ridge. Scutellum medium size, rugose, hardly bi-foveate, though 

 there is a scarcely discernible line dividing the large shining basal pit. Abdo- 

 men shining black, and of moderate size. The sheath of the ovipositor clear, 

 translucent brown. Legs dark brown. Wings hyaline : veins dark, the first 

 and second transverse heavy. Radial area short, broad and open, and with a 

 dark cloud at its base. Areolet wanting. Cubitus heavy and thickest at its 

 union with the first transverse. Body .08, antennas .06, wings .10. 



Seven specimens. 



Diastroplms minimum n. sp. 



Galls small, globular or oval blisters rising abruptly between the 

 nodes of the potentillae stems. They are not often more than .06 

 inch in diameter and contain one or two larval cells. They are 

 dark and smooth. 



Gall-flies. Females: — Black, except the legs which are a pale reddish brown. 

 Thirteen joints, first and second ovate, third straight, remaining joints short and 

 of uniform length. Thorax smooth and shining. Parapsides closely convergent 

 posteriorly. Scutellum medium size. Fovse large, shining and rather shallow. 

 Surface of the scutellum finely and regularly rugose. Abdomen smooth and 



TRANS. AM. ENT. SOC, XXVI. JULY 1900. 



