|Abstract or Summary
- The black grass bug genus Irbisia Reuter was revised. Over 18,000
specimens were examined and information concerning the biology, host
plant and distributional relationships of the species was compiled.
In addition to external characters, the male claspers and vesica, and
the female dorsal libiate plate of the bursa copulatrix and sclerotized
rings were used to distinguish the species. Sixty-nine characters
selected from male and female genitalia, and external morphology
were cladistically analyzed. Thirty-two characters are intracorrelated,
defining four species groups. Twenty-three species are
recognized in the genus. Two keys to the species are presented.
One new species, Irbisia knighti is described. The following
synonymies are proposed: I. brachycera (Uhler) = I. gorgoniensis
Bliven, I. paeta Van Duzee, I. tejonica Bliven, I. vestifera Bliven;
I. californica Van Duzee = I. eurekae Bliven, I. paenulata Bliven;
I. elongata Knight = I. retrusa Bliven; I. setosa Van Duzee = I.
ustricula Bliven; I. solani (Heidemann) = I. lacertosa Bliven.
Irbisia species diversity is greatest in the Coastal, Peninsular,
Sierra and Transverse Ranges of California and decreases northward,
northeastward and eastward. Major centers of endemism are located in
California and the Rocky Mountains northwest of the Wyoming Basin;
a minor center is located in the Siskiyou Mountains of southwestern
Oregon. Faunal similarity analysis suggests that the present Irbisia
fauna is derived from two source areas - one Californian, and one in the
Rocky Mountains. The present distribution of I. sericans (StS1) may
be derived from Beringian refugia. The distribution of the Irbisia
species appears to be delineated by climatic conditions; late winter
and early spring precipitation is required for growth of their cool
season grass hosts.
Over twenty native and introduced species of grasses are
utilized by larval and adult stages of Irbisia in Oregon. Larval
feeding was observed on four species of nongrass monocots, and
species of Lupinus and Lathyrus (Fabaceae). There appears to be no
grass host specificity among the Irbisia species. However, all the
grass species utilized are in the subfamily Pooideae; genera from
the Avenae, Poeae and Triticeae predominate. The Irbisia species
are the earliest mirid to consume the grass resource, completing their
life cycle before grass seed is mature. Many Irbisia species, upon
maturity, leave grasses and congregate on conspicuous nearby shrubs
and trees. Their dispersal is correlated with the blossoming of
these plants; adult feeding on pollen, nectar or honeydew is suspected.