46 BULLETIN 190, UNITED STATES NATIONAL MUSEUM 



yellow. Thorax black, with purple or blue luster ; patagia with a narrow 

 yellow stripe and a yellow patch beneath at wing base. Abdomen lustrous 

 violaceous or bronzy black ; segment 4 broadly banded and segment 7 nar- 

 rowly banded with yellow above only ; anal tuft short, halberd- or wedge- 

 shaped, entirely black. Posterior tibiae rough throughout, black, mixed 

 with yellow at and between the spurs; tarsi with first joints slightly thick- 

 ened, black; posterior joints sordid yellow. Forewing usually opaque, 

 lustrous violaceous-black, sometimes with a very small vitreous or suffused 

 yellowish area between the veins before, and a very narrow area behind, 

 the discal mark. Fringes broad, sordid black. Hindwing transparent, 

 narrowly margined and broadly fringed with brownish black; vein Ic 

 heavily scaled and thickened toward apex. Beneath, forewing heavily 

 shaded with yellow inwardly and less so outwardly from the discal mark. 



Female. — Very similar to the male but averaging larger in size and with 

 a heavier body. Only the fourth abdominal segment is broadly banded 

 with yellow above, and the black anal tuft is rounded with a short brush 

 projecting on each side. 



Expanse : Male 12 to 18 mm. ; female 13 to 23 mm. 



Distribution. — Eastern and Midwestern States, eastern Canada, 

 Southern States, and Gulf of Mexico coastal regions. 



Remarks. — C. pyralidifonnis is a root borer in Eupatorium, con- 

 fining its attacks, however, to species of the so-called bonesets and 

 thoroughworts — E. pcrfoUatum, sessilifoliuiii, and album. It has not 

 been found in the common joe-pye-weed, E. piirpureum. The larvae 

 tunnel in the upper rootstock and before pupating in July or later work 

 up into the bases of the stems to prepare the pupal chambers and the 

 usual circular apertures for exit. 



Hulst's nigella represents dwarfed forms of this species, which have 

 been traced to impoverished food plants growing in sterile, sandy soil 

 on hillsides. A majority of the several hundred specimens contained in 

 the United States National Museum collection are from Long Island, 

 the vicinity of New York City, New Jersey, and Pennsylvania in long, 

 reared series. Inland, inclusive of the Allegheny Mountains, the species 

 runs true in Virginia, the Carolinas, Ohio, Tennessee, to eastern central 

 Texas. At Myrtle Beach, Horry County, S. C, both typical pyralidi- 

 formis and the color form aurantis were collected September 20, 1937 

 (Engelhardt), indicating a transition zone. In addition to numerous 

 records from Mobile, Ala., September-October (Van AUer and Engel- 

 hardt), the form aurantis has been collected at Merrill, George County, 

 Miss., October 2, 1930 (Henry Dietrich), and there are several very 

 old examples in the United States National Museum labeled merely 

 "Texas." 



Type. — Female in the British Museum. 



