The Canadian Entomologist. 
MOL ive LONDON, ONT., FEBRUARY, 1872. No. 2 
DESCRIPTIONS OF NORTH AMERICAN HYMENOPTERA. 
NOTE: 
BY E. T. CRESSON, PHILADELPHIA, PA. 
Family ICHNEUMONIDÆ. 
Genus MESOCHORUS, Grav. 
Tuls genus belongs to the sub-family ‘‘ Ophionides,” of Holmgren, and is 
distinguished from all the other genera by the large, rhnomboidal areolet, 
or second submarginal cell, of the anterior wing. The abdomen is oblong- 
fusiform, slender at base, and more or less compressed at tip, that of the 
gf generally furnished with two slender setæ. 
The species are quite small in size, not exceeding three tenths of an 
inch in length, and are few in number. Those known to me may be 
tabulated as follows :— : 
Adomenventinely black. oi.) .6 i020). scence Rein rene ATRIVENTRIS, 
Abdomen black; with apical margin of second segment and the 
third entirely luteous : 
Large ; face and posterior coxe blackish....................04 AGILIS. 
Small; face dusky, with pale orbits ; posterior coxæ luteous..LUTEIPES. 
Abdomen black, with most of second and third segments lu- 
UC ONUS Peres SAR DEN IN SRE nate anid cre” st abatiotat Pen tray De, pt re Gueke a SCITULUS. 
_ Abdomen black, with apical half of second, and the remaining 
segments, except apical margins, luteous ................ AMERICANUS. 
Abdomen luteous or honey-yellow, with first and part of second 
segments black : 
Thorax above and occiput black ; second abdominal segment 
black, except narrow apical margin...................... BASALIS. 
Thorax and head entirely honey-yellow ; apical half of second 
abdominal segment honey-yellow........................ TOTONACUS. 
Abdomen luteous, with sides of first, and two oblique marks 
on base of second segment, black................,....... OBLIQUUS. 
Abdomen, thorax and head entirely honey-yellow............. MELLEUS. 
I. Mesochorus atriventris. N. sp.— §. Head yellowish-white ; anterior 
orbits, lower half of cheeks, mandibles and palpi, paler ; the front behind 
antennæ, vertex, occiput, upper half of cheeks and tips of mandibles 
piceous black ; antennæ nearly as long as the body, slender, blackish, 
