20 
AMERICAN SPECIES OF ARADUS (hEMIPTERa) 
interniccliatc pair are separated by the preeedin»:, and the lateral 
pair, always much abbreviated, occupy the postero-lateral angles 
of the pronotuin. In the figures these carinae are represented 
diagraininatically. The connexivuin is the marginal region of 
the abdomen. The distinct abdominal segments numlier six, 
to which is added in the male one genital segment, convex below 
and hollowed for the reception of the genitalia above, and con- 
tinued in two genital lobes. This is represented in the figures 
as seen from below, usually the apex only (except fig. 25b), but 
in cases of unusual modification (c/. fig. 471)), with the preceding 
segments. In the female tliere are two genital segments in addi- 
tion to the six abdominal, of which the first genital liears the 
female genital lobes and the second is very small (figs, la, Ig, 
2g, gl.). In observing the important specific characters fur- 
nisheil by the female genital structure, the following jioints, not 
referred to in the descriptions, should receive special attention 
(fig. 1): length of V on median line as compared with length of 
its lateral margin; shape of its apical margin at middk' (ap. in.); 
position of the imaginary line (xy) connecting the apical angles 
of VI with reference to the genital segments; length of ^T as 
com]:)ared with that of V on median line; shape of apical margin 
of VI at middle (cf. figs, la, 3a and 47a); shape of the lateral 
liortion of VI; relative lengths of VI, Ig and 2g; shape of the 
genital lobes. Very often important characters are afforded 
by the shape of the dorsal genital segment (fig. 12e, d. g. s.) and 
of the projecting genital lolies. Strongly costate longitudinal 
veins divide the coriuni of the hemielytra into three areas (fig. 
12(1), the cxocoriiim (ex), mesocorium (m), and endocorium (en), 
which may be strongly chitinized or hyaline, provided with nuni- 
ei'ous transverse veinlets or without them. 
It will be noted that in tlie di'scriptions a good deal of em- 
phasis is placed on the proportions of jiarts, often indicated by 
tigur('s in ])arentheses. The student will find it impossible to 
eslimate tlu'se ])ro])ortions with sufficient aciairacy and hence 
must mak(' use of an eyepiece mici’ometei' jilaced in one of the 
('yejiieces of the binocular mici-oscopi'. Th(' examination of ven- 
li’al struct ur('s is gi'eatly facilitat(Ml by the use of “ai't-gum” 
or some such soft substance, into which the head of the pin may 
