2 E. T. CRESSON. 



be gone over many times before anything approaching perfection can 

 be arrived at ; but this is the case with all families of insects where 

 the species are very numerous and the generic and specific characters 

 so improminent as in this great family. 



When studying and cataloguing the species of the genus Ichneumon, 

 collected north of Mexico, (having at the time very few from south of 

 that line.) I had but little diiBculty in deciding what species properly 

 belonged to that genus, and Hojjlismenus, Joppa and Trocpis seemed 

 to me to possess characters by which they could be readily separated 

 from Ichneumon and from each other ; but since the examination of 

 the collection now under consideration from Mexico — a recent arrival — 

 I find so many intermediate forms, that I actually hesitate to say what 

 is an Ichneumon, an Iloplismenus, a Joppa, or a Trogua. If I confine 

 myself to typical generic forms, I have left a number of species I feel 

 at a loss to say to what genus they properly belong. In this dilem- 

 ma, I have for the present compromised the matter in my own mind 

 by provisionally retaining all the four above named genera, and placing 

 in them such species as seem most natural, and referring the most 

 doubtful species to Ichne.umon. This seems to me the best plan to 

 adopt for the present and until a more elaborate study can be made 

 of their natural afiinities. 



Family ICHNEUMOXID^. 

 Genus ICHNEUMON, Linn. 

 Metathorax without prominent lateral tubercles. 

 Scutellum flat or moderately convex. 



Abdomen red, or red and black Sp. 1 — 2 



" black, banded with white or yellow 3 — 16 



Scutellum more or less elevated. 



Abdomen red 17 — 18 



" yellow, banded with black I'J — 21 



" entirely yellow — 22 



Metathorax with prominent lateral tubercles. 



Scutellum flat or subconvex 23 — 32 



" decidedly convex. 



Abdomen red and black — 33 



" black, banded with yellow 34—36 



Scutellum much elevated 37 — 38 



1. Ichneumon mexicanus, n. sp. 



% 9 . — Black, head and thorax shining; face, mouth, orbits, broad 

 on the cheeks, annulus on antennae, basal joint beneath in S , posterior 

 margin of prothoras, broader before the tegulae which has a spot in 



