ArticLte VII.—The Pentatomoidea of Illinois, with Keys to the 
Nearctic Genera.* By CHarLtes ARTHUR Harr. 
° 
INTRODUCTORY 
In 1898 Prof. H. E. Summers prepared the first key in English to 
the American pentatomid genera * *, using the collection of the Illinois 
State Laboratory of Natural History (now Division of Natural History 
Survey). The key was based on Stal’s keys, but, as Van Duzee says, 
“contains much original work.” It seems appropriate that this collection, 
greatly increased since 1898, and that of the University of Illinois should 
now serve for a revision of the subject. In identifying species and con- 
structing keys to them, Van Duzee’s “Annotated List” + has been of the 
greatest value. In the general grouping I have agreed closely with 
Kirkaldy’s views.t 
The commoner species form homogeneous groups and are easily dis- 
posed of in keys, but there are a number of rare and little-known species, 
scattered representatives of important exotic groups, to which I wish to 
direct especial attention—although their inclusion complicates the classi- 
fication—in order that further knowledge of them and their distribution, 
either in Illinois or elsewhere in the United States, may be particularly 
searched for. : 
In the arrangement of my keys I have tried to show the natural 
grouping and succession, because I believe that an artificial grouping, 
although apparently simpler, often obscures or suppresses the more diff- 
cult yet essential points of difference, and is of little value in the ex- 
tension of knowledge. In characterizing groups, I have not necessarily 
taken into account extralimital forms. The term “segment” is often to 
be understood after such combinations as second antennal, rostral, tarsal, 
etc. ; and the words dorsal and ventral, similarly used, refer to the abdom- 
inal segments. The term “elytra” is used as a convenient term for thick- 
ened opaque fore wings generally. 
* The manuscript of this paper was only partially complete at the time of Mr. 
Hart’s death. Its final preparation was undertaken by J. R. Malloch, and where addi- 
tions to the original are made, whether in the form of records of species, or notes, or 
amplifications, these are indicated by brackets, either in the regular text or in foot- 
notes. 
* * Proc. Iowa Acad. Sci., Vol. 6, p. 40. 
+ Trans. Am. Ent. Soc., Vol. 30, No. 1. [Van Duzee’s Catalogue of Hemiptera 
(Univ. Cal. Pub., Tech. Bul. Coll. Agr., Agr. Exper. Sta., Vol. 2, 1917) appeared but a 
short time before Mr. Hart’s death, and synonyms therefrom have in some cases been 
added to the paper by the editor. The citations to original descriptions are also addi- 
tions by the editor, nearly all of them being made direct from the publications in which 
the descriptions occur, the above-named catalogue serving admirably, however, as an 
aid in locating them.] 
= Cat. Hemip. (Heter.), with Biol. and Anatom. References, p. 363. 
