IOS TRANS. ST. LOUIS ACAD. SCIENCE. 



Genus RHYSSA, Grav. 



In this genus the bulla A is absent, B is located at the lower 

 end of its cross-vein, C and D are wide apart, and E is nearer than 

 usual to the angle of the first recurrent vein. Judging from the 

 only species — Rh. huiator, Fabr. — of which I possess numerous 

 specimens, the amount of colorational variation is small, but the 

 variation in size is very great, some <$ specimens being \ longer 

 than others, and the ovipositor in one of my specimens being only 

 \ longer than the body ; while in others, according to Brulle, it is 

 nearly twice as long as the body. 



Rhyssa atrata, Fabr., and Rhyssa lunator, Fabr. — This last 

 does not occur near Rock Island, 111. ; but I took numerous spe- 

 cimens in South Illinois, in the beginning of July, flying round a 

 hickory log, and I have also seen specimens in Mr. Bolter's col- 

 lection at Chicago. 



Rhyssa [(pimfila) humida, Say, Bost. Jour. ii. p. 224]. — $. — Black. 

 Head with broad, white orbits, which are widely interrupted on the ver- 

 tex and narrowly at the insertion of the antennae, where the white color 

 is replaced by a shallow, square depression with a glassy, semipellucid, 

 lead-colored lustre. Palpi white. Antennae brown-black, § as long as 

 the body. Thorax with the transverse rugae coarse; the tegulae, a large 

 oblong spot under the front wing, and a very large triangular spot before 

 it prolonged at the tip in a line as long as the triangle itself and the whole 

 adjoining the humeral suture below, a line above the anterior coxa', a pair 

 of parallel lines arranged side by side longitudinally on the disk of the 

 mesothorax and half as long as the mesothorax itself, the lateral and hind 

 margin of the scutel, and two round subconfluent spots transversely ar- 

 ranged on the postscutel, all white. Metathorax very finely rugose, pol- 

 ished, with a longitudinal acute stria deeply impressed in front and fading 

 out behind. Meso- and meta-sternum and their entire pleura glabrous 

 and polished, pale rufous, except that on the terminal £ of the metathora- 

 cic pleura there is an elongate white spot separating the black color from, 

 the rufous. Abdo?nen polished, with very fine transverse rugae ; joint 1 

 with a shallow, wide dorsal stria extending nearly to its tip, and basally 

 wider and deeper; joints 2-7 each with a lateral, subterminal, roundish, 

 white spot, which in 2 is a mere white dot, and becomes larger in each 

 successive joint, till in 6 and 7 it not only covers nearly the whole length 

 of the joint, but extends upwards so as to be respectively 2 and 3 times as 

 wide as long; joint 8 highly polished and tapered to a conical point be- 

 hind, the cone about as long as joint 7 and flattened below. Ovipositor 

 piceo-rufous, a little longer than the body, its sheaths black both inter- 

 nally and externally. Venter, with the tip of the joints, whitish. Legs 

 pale rufous, the anterior trochanters whitish; the knees, tibiae, and tarsi. 



