NORTH AMERICAN HYMKNOPTERA. 



197 



The sti<inm\>{ its forewiiig is a semi- 

 circular, black, shining spot with a small 

 appendage on the inner side of its hind 

 end and its base slightly separated from 

 the robust subvein, which vein is of a 

 dark or black color. 

 ^ipalau^ia «lorsalis Fitch. 

 Specimens freqviently occur so very 

 different in their colors that they might 

 l)e deemed a distinct species. They may 

 be termed the line-backed variety dor- 

 .srt/is of the oak wool parasite. In them 

 the thorax is pale greenish-yellow with 

 a black stripe along its middle, and the 

 abdomen is yellow, with the back black, 

 and commonly with black bands upon 

 its sides. 



Wings hyaline; veins brown ; stujma 

 blaclc. No vestige, whatever, of any 

 stigniatic cloud or patch. 



Decatoina siniplicisligma 



Walsh.- '& 9. Pale ochre yellow. 

 Head subopaque, confluently and vei-y 

 coarsely punctate ; disk of the occiput, 

 ocelli and which is rarely H % 1 9 ) 

 confluent by a narrow tongue with the 

 occipital spot, all black. Antennne with 

 the flagellum slightly obfuscated above. 

 Thorax sculptured as the head, but 

 still more coarsely. Collar rarely (1 9 ) 

 with a narrow dorsal black line ; meso- 

 notum with a more or less slender 

 dorsal black triangle, the base of the 

 triangle usually starting from the su- 

 ture behind the collar, sometimes from 

 the hind part of the collar, and the 

 apex of the triangle approaching more 

 or less nearly, but never quite attaining 

 the scutel. Occasionally on each side 

 of this black triangle two or three 

 black dots are placed in the suture 

 behind the collar. On the scutel a 

 more or less wide dorsal black line not 

 i quite attaining its tip. Very rarely 

 i (19) the entire mesonotus is immacu- 

 1 late, mesothorax always with a more 

 or less wide dorsal black line, wliich is 

 almost always proloned in a curve 

 i behind the mesothoracic scutel to the 

 origin of the front wing. Abdomen 

 I highly polished, with the peduncle 

 -^"9 as in varians. the yellow color 

 often merging more or less into rufous. 

 Peduncle above and below, a dorsal, a 

 dorsal line not attaining the tip. which 

 generally ex])ands upon each suture 

 into a lateral tooth, and is sometimes 

 dilated into one large dorsal patch, all 

 black. Legs immaculate, but the su- 

 ture at the origin of the hiud coxa; is 

 black. Wings hyaline; veing brown : 

 stiguui black ; no vestige of any stig- 

 mrtic cloud or patch. Length % .06- 

 .11 inch. 9 '^^ -^1 '"*'^^- 



