8 
AMERICAN SPECIES OF ARADUS (hEMIPTERA) 
pronotal sides and rather short seiiital lobes in the female. Ro- 
bi(stus has a characteristic pronotal shape, very thick antennae, 
and long, widely distant female genital lobes, hitcctus leads to 
(hizeei, etc , with entire pronotal margins. The species to im- 
planus have a long first genital segment in the female; then fol- 
lows a series with the first genital short and with the antennae 
thinner, leading toward the next group. 
Prohoscideus Group. — Antennae slender and cylindrical, the 
second segment much longer than the third; form of body rather 
elongate; corium strongly dilated at liase. There are two types 
of pronotal structure: the species to co7isors have the dorsal 
surface relatively fiat; in the rest the anterior region is strongly 
elevated, the transverse impression deep. The extreme develop- 
ment in length and slenderness of antennae is reached in dehdis, 
while cincticorms and parvicornis manifest a tendency to re- 
duction. 
Similis Group. — Antennae slenderly clavate, the second seg- 
ment enlarging usually from near base and variable in length, 
but always much longer than the third; general form distinctly 
elongate, the abdomen often narrowed posteriorly in the female; 
corium strongly dilated at base. Opertaneus is intermediate in 
some respects lietween this and the preceding group, especially 
in antennal structure. In the last four species the first genital 
segment of the female is very short, recalling the condition in 
dPtilis and allies. 
Cotnpresms Group. — Pronotum flattened, the lateral margins 
entire; second antennal segment clavate; corium moderately di- 
lated at base; form rather broad. 
Tid^erculifei' Group. — This group is more than usually ill- 
defined, and consists of three species intermediate with respect to 
the degree of expansion of the corium between the iireceding 
and following sections. The pronotum is rather fiat, with entire 
margins, and the antennae are slenderly clavate, almost linear 
in funestui^. 
JAupdrri.H Gi'oup. — Pronotal margins generally sinuate antei'ioi'ly 
and entire or granulati'; foi'in nari'ow; second aidi'imal si'gnu'iit 
narrowed towai’d bas(' or almost liiK'ar; head ])rovid('d with 
oblicpH' ])al(‘ liiu's at b:is('; tlu' ])ost()culai’ IuIhm'cU's slight or 
