Plagiognathus politus, Uhler, 1895

SCHUH, RANDALL T., 2001, Revision Of New World Plagiognathus Fieber, With Comments On The Palearctic Fauna And The Description Of A New Genus (Heteroptera: Miridae: Phylinae), Bulletin of the American Museum of Natural History 2001 (266), pp. 1-267 : 17-19

thus politus Uhler —are the ones most fre­

quently encountered by general collectors sweeping herbaceous vegetation, and they are therefore very common in collections. Hosts are not well documented for many North American Plagiognathus spp. , irrespective of their feeding habits, which makes determining species limits within the group more difficult than might otherwise be the case.

Although many species, such as obscurus and politus , are extremely common in collections, documenting the hosts and life histories of these and other Plagiognathus species will require a tremendous amount of additional fieldwork. One only has to examine the works of Knight (1923, 1941) on the faunas of Connecticut and Illinois to realize that the habits of many species were (and still remain) poorly understood. The fieldwork of A. G. Wheeler, Jr. and T. J. Henry, primarily in Pennsylvania, and that of L. A. Kelton in eastern Canada has added a tremendous amount of new information to what was available 60 years ago, as can be seen from examination of the species treatments in the present paper; nonetheless, the habits of some species still remain obscure. I had presumed that a modern treatment of the group, including the examination of material and host records ranging from the Hemiptera of Connecticut (Knight, 1923) to the present, would clarify the nature of host associations for most, if not all, species. Such has not been the case. Regardless, the following issues have been clarified.

It is now apparent that a significant number of Plagiognathus species feed on conifers. Previously, several of the conifer­feeding species from eastern North America had been placed in other genera, notably Microphylellus ; virtually no species with such habits were known from the West. Now at least 8 species are known to feed exclusively on the Pinaceae . One would expect to see the discovery of additional conifer­feeders in the West with further collecting. Many of the species recorded here, as well as those described in Plagiognathus , but treated by Schwartz and Schuh ( 2000) as belonging to other genera, are seldom encountered, even by the specialist collector. Conifer­feeding in Plagiognathus appears to have arisen several times because species with such habits belong to several of the species groups delimited above. This can be easily seen by comparing species such as concoloris , fenderi , laricicola , and tsugae , all of which have well­documented hosts, but which certainly do not show close phylogenetic relationships to one another within Plagiognathus . Host information as recorded in the present publication is what I found on the specimen labels. I have made only a very limited number of decisions concerning the admissibility of host label data. The picture that emerges—either as a consequence or as a matter of fact—is that for many species the breeding hosts are not obvious. What is clear, however, is that Plagiognathus spp. feed on a broad range of plant groups; they do not show the restrictions seen in recently revised groups such as Oligotylus Van Duzee (Schuh, 1999) and Megalopsallus Knight (Schuh, 2000) .

The plant families and the numbers of Plagiognathus species feeding on them can be summarized as follows. Some Plagiognathus species feed on members of more than one plant family. Single specimen records are excluded.

Plant Number of

family Plagiognathus species Aceraceae 2

Anacardiaceae 8

Apiaceae 5

Asclepiadaceae 1 (single host record) Asteraceae 13

Berberidaceae 1

Betulaceae 9

Boraginaceae 1

Brassicaceae 2 (both as alternate hosts)

Caprifoliaceae 7

Cornaceae 3

Eleagnaceae 3

Ericaceae 5

Fabaceae 15

Fagaceae 7

Geraniaceae 1

Gesneriaceae 1 (single host record; males only) Grossulariaceae 4

Hamamelidaceae 1 (single host record) Hydrophyllaceae 3 (1 species from single host record) Hydrangeaceae 1 (single host record) Juglandaceae 2

Lamiaceae 7

Liliaceae 1 (single host record) Malvaceae 2 (both as alternate hosts)

Myricaceae 2

Nyssaceae 2

Oleaceae 4 (1 species as alternate host)

Pinaceae 8 (other nonbreeding records not noted)

Platanaceae 1

Ranunculaceae 2

Rhamnaceae 1 (probably alternate host)

Rosaceae 16 (approximately)

Salicaceae 11

Scrophulariaceae 3

Ulmaceae 3 (approximately)

Urticaceae 2

Verbenaceae 1

Vitaceae 1 Of the 39 plant families listed, probably

eight represent nonbreeding records or plant

groups that are rarely used as hosts.

DISTRIBUTION

In the Nearctic, Plagiognathus is one of the most diverse groups of Miridae at latitudes above about 40 degrees north. This can be easily seen by examining Kelton’s (1980) work on the Miridae of the Prairie provinces in which Plagiognathus spp. dominate the phyline fauna. My own fieldwork corroborates this general pattern, where much of the Plagiognathus material was collected at higher latitudes, and to a limited degree at higher altitudes (at lower latitudes). This pattern of latitudinal distribution is not quite so obvious in the Palearctic, but then the numbers of species there are much smaller.

What is apparent, in contrast to some other groups of Phylinae —such as Chlamydatus Curtis and Europiella Reuter —which are also most diverse at higher latitudes, is that there are no truly Holarctic species of Plagiognathus . Probably three species of Chlamydatus (pulicarius (Fallen), pullus (Reuter), wilkinsoni (Douglas and Scott)) (see Kelton, 1965) and at least two of Europiella ( artemisiae (Becker) , decolor (Uhler)) (see Schuh et al., 1995) are Holarctic. The three species of Plagiognathus that occur in both the Palearctic and Nearctic— arbustorum (Fabricius) , chrysanthemi (Wolff) , and vitellinus (Scholtz) —all appear to be introduction into North America (Wheeler and Henry, 1992). In the case of arbustorum this conclusion is supported by the very narrow distribution of the taxon in the Pacific Northwest, which is not continuous with the distribution of the species in the Palearctic. The situation with chrysanthemi may not be quite so clear­cut, but its introduced status is suggested by its breeding on introduced ruderals and its being limited to the Northeast and the Northwest. Plagiognathus vitellinus has achieved a relatively broad distribution in the Northeast and is known to breed on Picea and some other conifer species native to North America. It does not, however, belong to any of the species groups of Plagiognathus that occur only in North America, suggesting that it is not an indigenous species, an argument that can also be made for chrysanthemi (see also discussion of these taxa in Wheeler and Henry, 1992).

Furthermore, up to the time of completion of the present paper, Plagiognathus appeared to be largely restricted to eastern North America and, as noted above, to higher latitudes; however, such a characterization is clearly not accurate.

First, it is now clear that there is a substantial component of species restricted to the southern United States. The biologies of the species newly described from this area are not known, most of the available specimens having been taken at lights or without host data. With additional specialized collecting, we might expect to see even more species from this area, whereas diversity at higher latitudes in eastern North America appears to be quite well sampled.

Second, some taxa that would formerly have been characterized as being restricted to eastern North America are now known to have much wider distributions. These include Plagionathus alboradialis Knight , P. brunneus (Provancher) , P. fuscosus (Provancher) , P. obscurus Uhler , and P. parshleyi Knight. In all cases the distributional extensions are primarily at higher latitudes and in some cases also at higher altitudes at lower latitudes.

Third, the fauna of the western United States is now shown to be diverse and broad ranging in the region. Some species, such as those belonging to the concoloris , lattini , and ribesi species groups, are restricted to the West. Other western taxa, such as P. fenderi , new species and P. notodysmicos , new species, appear to have their closest relatives in Eastern North America.

Finally, examination of locality data in the present paper might suggest that Plagiogna­