APPENDIX. 311 



tennse and extending between the eyes is a transverse 

 black spot; thorax each side above the base of the supe- 

 rior wings with a longitudinal blackish spot, connected be- 

 hind with a transverse, almost indefinite one ; metathorax 

 blackish behind ; wings hyaline, slightly tinged with yel- 

 lowish, nervures brown ; tergum, three basal segments 

 black, remaining segments obsoletely blackish on their 

 posterior margins ; posterior pairs of tibiae six-spined, one 

 on the middle, one beyond the middle, and the other at 

 tip. 



Length to tip of oviduct seven-twentieths of an inch. 



This interesting insect was presented to me by Mr. Tho- 

 mas Nuttall, who obtained it during his expedition to Ar- 

 kansa. The forms of some of the wing cellules differ a 

 little from those of the type of this genus. The first radial 

 cellule receives the first recurrent nervure and is nearly 

 square, slightly oblong, and nearly two-thirds the size of 

 the second cellule, which receives no recurrent nervure 

 and is somewhat smaller than the third cellule. The lat- 

 ter receives two recurrent nervures. The cubital cellules 

 are sub-equal, bounded beneath by an almost rectilinear 

 line, the third nearly attains the tip of the wing, leaving 

 the fourth cellule very small. The maxillary palpi also 

 are much shorter than those of the Swedish species. This 

 disposition of the nervures will authorize the formation of 

 a distinct section in the genus. 



XIPHYDRIA, Latr. 



1. X. abdominalis. Black; abdomen rufous. 

 Inhabits Pennsylvania. 



Head confluently punctured ; antennsa short ; vertex 

 with two distant, longitudinal, yellow spots, and another 



