52 IOWA STUDIES IN NATURAL HISTORY 
a little behind the midcoxae. It is not prolonged into a single 
groove but a number of crenulated ridges radiate in a fan- 
shaped pattern from the opening and terminate abruptly at the 
outer one-third of the metapleurae, thus forming a series of 
grooves. 
Subfamily PENTATOMINAE (Stal) 
This subfamily is very widely distributed, attaining its great- 
est development in point of size, coloration and numbers in the 
tropical parts of the Old World. It is also the best represented 
subfamily in the New World and in North America it is made 
up of about 150 forms which are placed in thirty-eight genera. 
In the present state of our knowledge the subfamily is repre- 
sented in Iowa by thirty-five forms which are disposed in twenty 
genera. 
Practically all the members of the group are plant feeders 
in both nymphal and imaginal stages and, as a consequence, 
some of the species are of considerable economic importance 
particularly in the South. In lowa, however, no species of the 
subfamily is ordinarily present in sufficient abundance in any 
locality to cause material damage. A few species are, in part, 
predaceous in feeding habits. The differential characters of 
the subfamily include the following: 
Bucculae long, parallel. Basal segment of rostrum usually slender and 
largely embedded between bucculae but extending beyond their apices; ros- 
trum inserted a little behind tip of tylus. Pronotum without teeth or with 
numerous teeth near antero-lateral angles. Scutellum not exceeding corium 
in length and more or less narrowed at apex. Frena usually more than one- 
third the length of the scutellum. 
Key to the tribes 
Body very long, linear: second antennal segment dilated on 
inner side; sides of base of venter with a finely striated stridu- 
latme area... 2s.k 4h oie. OS Pe ee eee MEcIDIINI 
Body more or less ovate, not extremely elongate and linear: 
second antennal segment not dilated on inner side; venter with- 
out striated stridulating spot at sides of base 
Abdomen with a shallow, longitudinal ventral suleus; rostrum 
extending behind posterior coxae; juga with a prominent 
lateral tooth “néar apex: ). 5.22552... 22 eee HALYINI 
