AMERICAN HYMENOrTERA. 129 



Notes on the species belonging to the snbl'uniily 

 ICHNEUIVIONIDES, found in America north of Mexico. 



BY E. T. CRESSON. 



In the first volume of these Transactious Cp. 289), I began the 

 publication of a list of the Ichneuuionidfe of North America, intend- 

 ing to continue it from time to time until completed ; but after the 

 printing of the second part (vol. ii, p. 89), the acquisation of new 

 and more abundant material made it necessary that the work should 

 be gone over again, and suggested many important changes, which 

 render the lists given in the two parts of but little value. I have not 

 since attempted a revision of the subject, prefering to wait for larger 

 collections, and further knowledge of the economy and habits of the 

 species. The great dissimilarity in color between the sexes in many 

 cases — as shown in the European species — renders it extremely diffi- 

 cult and unsafe to corelate them; this, however, can only be deter- 

 mined upon by actual observation and by breeding, and will require 

 years of patient labor, chiefly in the field. 



In the present paper, which is intended merely to assist the student 

 in separating the species, I have included only those known to me as 

 having been found north of Mexico, which are of themselves very 

 numerous, prefering to make at some future time a separate list of the 

 subtropical species, which exhibit a still greater variation in form. 

 A list of the Mexican species has already been given in the Proceed- 

 ings of the Academy of Natural Sciences, 1873, p. 104, etc. 



In lieu of a more satisfactory division of the subfamily, I have for 

 the present adopted that given by Holmgren in his Ichncumonologia 

 Suecica, which is as follows : — 



Metathoracic spiracles linear or oval. 



Petiole of abdomen not depressed, not broader than high. 



Abdoii.en 9 acute at tip, last ventral segment retracted ; % ventral seg- 

 ments 2— 4 with longitudinal fold Ichneumonides oxypygi. 



Abdomen 9 obtuse at tip, last ventral segment slightly or not at all re- 

 tracted ; % ventral segments 3 — 8 or 4 — 8 flat, smuoih, witliout longitudi- 

 nal fold Ichneumonides amblypygi. 



Petiole of abdomen depressed, broader than high. ...Ichneumonides platyuri. 

 Metathoracic spiracles circular Ichneumonides pneustici. 



TRANS. AMER. ENT, SOC. VI. (18) JILY, 1877. 



