22 IOWA STUDIES IN NATURAL HISTORY 
vein running paraliel to margin of corium. Corium more or less narrowed. 
Basal segment of venter very narrow, entirely or almost entirely covered 
by metasternum. Connexivum of abdomen with six visible dorsal seg- 
ments. Tibiae more or less strongly spinose, the spines arranged in rows. 
Tarsi 3-segmented. 
Key to subfamilies 
Scutellum broad, convex, covering most of the abdomen and 
longer than the corium ; apex of corium narrowed THYREOCORINAE 
Scutellum triangular, narrowed at tip, more or less flattened and 
shorter than corium; apex of corium broader........ CYDNINAE 
Subfamily THYREOCORINAE (Van Duzee) 
The insects, sometimes called ‘‘negro bugs,’’ which comprise 
this subfamily although apparently superficially quite unlike 
the members of the subfamily Cydninae, do have important 
structural modifications which entitle them to be placed in the 
same family. But one genus containing seventeen species is re- 
eorded from North America. Four of the species are widely dis- 
tributed over the United States but the others are more partic- 
ularly characteristic of the West and Southwest. Five species 
have been taken in Iowa. All but one of the North American 
species are black. In all, the scutellum is rather deeply convex 
and entirely or almost entirely covers the abdomen. 
Our forms are usually found on vegetation growing in damp 
places although Thyreocoris mtiduloides is often present on the 
dry prairies. The short grasses and weeds about the edges of 
woods and cultivated fields frequently yield numbers of these 
bugs. Thyreocoris pulicarius sometimes attacks cultivated plants 
and under favorable conditions its numbers may so increase that 
the species becomes a real pest. The principal characters of the 
subfamily are as follows: 
Body oval, convex. General color usually deep black or bronzed black. 
Head more or less triangular. Antennae of five segments. Scutellum 
very convex, longer than corium, broadly rounded and entirely or almost 
entirely covering abdomen. Apex of corium narrowed. Non-fossorial. 
Tibiae furnished with spines, usually slender; few long hairs. 
Genus THYREOCORIS Schrank 
1801. THuyreocoris Schrank, Fauna Boiea, II, 46. 
General form more or less ovate, very convex. Head large, anterior 
border straight or slightly sinuate. Antennae longer than head, the sec- 
