J. H. MERRILL 109 



ON SOME GENERA OF THE PIMPLINE 

 ICHNEUMONIDAE 



by j. h. merrill, ph.d. ^ 



Introduction 



This paper is the result of three years' work done at the Massa- 

 chusetts Agricultural College as a partial requirement for the 

 degree of Doctor of Philosophy. 



I wish to acknowledge my obligations to Dr. H. T. Fernald, 

 under whose direction this work was carried on, to C. H. Fernald 

 for his kindly suggestions, to Dr. G. C. Crampton for valuable 

 advice and criticism, to W. S. Regan for the valuable assistance 

 rendered me l)y securing specimens for study from the museums 

 at Philadelphia, Washington, and New York, and making notes 

 on the comparisons of these insects with their types, and to Dr. 

 C. Gordon Hewitt for the loan of a large number of specimens. 



Mr. F. A. Johnston began work on this group and had brought 

 together copies of the descriptions of nearly all the insects treated 

 here, when he accepted a position with the Bureau of Entomology, 

 and the subject was given to me to continue. 



Fourteen species and four genera are treated here. Of these, 

 one genus and one species are described for the first time. Most 

 of the other North American species are redescribed, wherever it 

 was possible to obtain specimens from which to make the descrip- 

 tions. The genus Epirhyssa has been abandoned, as it did not 

 seem to have enough distinctive generic characteristics to sepa- 

 rate it from Rhyssa. A new genus Pseudorhyssa has been estab- 

 lished. Its transversely wrinkled mesonotum places it within 

 the scope of the genera treated here; the entire sternal plates 

 of its abdomen, however, separate it from the other genera. 

 The type of this genus, Pseurhrhyssa sternata is here described. 

 The description of Thalessa histrio, an unlocated species, is also 

 included. 



Probably the largest and most valuable collection in this 

 country of the insects treated here is at the Academy of Natural 



' Contribution from the Entomological Laboratorj' of the Massachusetts 

 Agricultural College, Amherst, Mass. 



TRANS. AM. ENT. SOC, XLI. 



