September, 1941 
lettia amoena (Uhler) from an area which 
abounded with the ant, Formica (Neofor- 
mica) pallide-fulva var. incerta Emory. The 
wingless females so resemble this ant in 
form and color that one must look rather 
closely to separate them. Miridae of the 
above species of Sericophanes and Coquil- 
lettia are extremely agile and very rapid of 
movement, especially when they happen to 
meet face to face with ants. While they 
seem not to fear the ants, they appear to 
avoid close contact with them. 
Systematic Characters 
The most important character for sepa- 
ration of subfamilies is found in the struc- 
ture of the arolia, situated between and at 
the base of claws, fig. 17. In the subfamilies 
Phylinae and Deraeocorinae the arolia are 
represented by a pair of erect bristles that 
are difficult to see in the smaller species. 
The arolia are erect and well developed in 
the Orthotylinae, Mirinae and Capsinae; 
arolia converging at tips in Orthotylinae and 
diverging apically in the Mirinae and Cap- 
sinae. Pseudarolia are clear to white in 
color and occur on inner curvature of claw 
near base. The pseudarolia are found in 
the Phylinae but are larger and more prom- 
inent in the Dicyphinae and Bryocorinae. 
The form of the male genital segment is 
rather distinctive in the subfamily Phylinae; 
the genital claspers are relatively small, with 
tip of right clasper resting in a notch across 
the middle of the V-shaped left clasper; both 
oedagus and claspers are twisted somewhat 
to the left side. The author believes this 
particular form of genital segment is a fun- 
damental character of this subfamily. In 
other subfamilies the male genital segment 
often presents good characters for the sepa- 
ration of genera as well as species. Specific 
differences are more likely to be found in 
the male claspers, which are asymmetrical 
in form and differ among the species in many 
genera. It is fortunate that in several of the 
largest genera the numerous species may be 
identified by the form of the genital claspers, 
as in Phytocoris, Neolygus, Lopidea, Ortho- 
tylus, Ceratocapsus and Deraeocoris. On 
the other hand, in several sizable genera 
such as Paracalocoris, Neurocolpus and 
Neoborus the male genital claspers appear 
to be of little value for distinguishing species. 
Fortunately, in Paracalocoris and Neurocol- 
pus the length of antennal segments and 
KNIGHT: PLANT Bucs, or MIrIDAE, OF ILLINOIS 17 
form of pubescence offer very good charac- 
ters for separating species. Thus it appears 
that a particular set of characters may not 
have equal value throughout the family. 
Among the Miridae, pubescence often pro- 
vides useful characters; it varies from sim- 
ple, fine hairs, erect or recumbent, to silky, 
slightly curled pubescence, or even flattened, 
scalelike hairs. The scalelike pubescence 
found on several species of Phytocoris and 
in the genus Halticus is easily shed or lost; 
hence specimens should be collected and 
preserved with great care. 
The shape of the head and thorax is much 
used for generic characters; minor differ- 
ences may indicate species. The length of 
the rostrum may be of generic value but 
more frequently it differs among the species 
and may form good distinctions, as in Po- 
lymerus and Lygus. The antennae are gen- 
erally linear in form with the last two seg- 
ments very slender. However, some genera 
may be separated by the exceptional form 
of the different segments; the second seg- 
ment is strongly thickened in Capsus, Atrac- 
totomus and Teleorhinus; the third and 
fourth segments are usually slender, but in 
some genera, as Ceratocapsus, they are dis- 
tinctly thickened. 
Phylogeny 
Nine subfamilies of Miridae are recog- 
nized from North America and all of them 
are found in the state of Illinois. The 
DIC VY PHINAE 
BRYOCORINAE 
CYLAPINAE 
CLIVINEM/NAE 
DERAEOCORINAE 
ORTHOTYLINAE 
PHYLINAE 
Fig. 18.—Genealogical tree showing relation- 
ship of mirid subfamilies. 
phylogeny of these subfamilies does not pre- 
sent a linear series of development, but more 
of a progression upward in several direc- 
tions, which perhaps may best be represent- 
ed by a genealogical tree, fig. 18, to express 
the relationships within the family. These 
relationships are based on the following 
characters, which are listed in the order of 
their relative importance: (1) arolia, (2) 
