This insect of the week posting, Metcalfa pruinosa (the citrus flatid planthopper), celebrates the 1 May birthdate of Zeno Metcalf, affectionately known as “Zippy” by a few modern workers. The name Zeno Payne Metcalf (1 May 1885 to 5 January 1956) is forever linked to the study of planthoppers, cicadas, spittlebugs, leafhoppers and treehoppers (Hemiptera: Auchenorrhyncha) and to North Carolina State University. Thus, the genus Metcalfa is but one of several insect taxa named for Metcalf, who also has a website and an NC State dormitory named in his honor. Metcalf amassed a worldwide collection of his beloved insects, which formed the heart of the NCSU Insect Museum, and the world’s most comprehensive collection of literature on these plant-feeding insects, now a key component of the NCSU Libraries’ Special Collections. Metcalf headed NC State’s Department of Entomology and Zoology for nearly 40 years. He is internationally known for his 42-volume “General Catalogue of the Homoptera of the World” and its associated bibliographies (Metcalf 1944-1968). During his distinguished career, Dr Metcalf also served as President of the Entomological Society of America, the Ecological Society of America, and the American Microscopical Society, and as the Director of NC State’s Graduate Studies (3 years) and Associate Dean of the Graduate School (7 years).

Thomas Say (1830) described our featured insect as Flata pruinosa. Subsequently the species was variously referred to the genera Poeciloptera , Melormenis, Ormenis, and most recently Metcalfa, a genus described in honor of Z.P. Metcalf in 1951 by Caldwell and Martorell (with F. pruniosa as its type species). Metcalf’s flatid catalog (1957) listed nearly seven pages of references on this insect covering the literature through 1955. An account of planthoppers in general, including selected links and recent references, is found on the NCSU DrMetcalf Website.

Specimens of Metcalfa pruinosa vary from 5.5 to 8 mm in length and 2 to 3 mm across at the widest point. At rest, the broadly triangular forewings are held vertically against the body, giving the insects a wedge-shaped, laterally compressed appearance. In the forewing, the costal cell has numerous crossveins and the clavus is granulate. The hind tibiae have two lateral spines in addition to apical spines. Like many other flatid planthoppers, these insects resemble acanaloniid planthoppers, which lack the numerous costal crossveins, the granulate clavus, and the lateral spines of the hind tibiae.

Adults of M. pruinosa vary in color from brown to gray, owing in large part to the thickness of their covering of waxy secretions (see photos below). Individuals may have more or less the bluish white waxy powder and this waxy pruinosity is the likely source of the specific name “pruinosa.” Eyes are typically red. A pair of dark spots on the basal half of the forewing is another key feature of the species. Nymphs of many Fulgoroids produce wax from special glands on the abdominal terga and other parts of the body. Such waxy secretions are hydrophobic and may serve as a means of camouflage.

Mature nymphs are nearly 4 mm in length, excluding their fragile waxy filaments. Earlier stages are smaller, depending on the instar, but are generally less than twice as long as wide.

Dead specimen from the NCSU Insect Museum Collection

Living Specimen with color change due to waxy covering.
Copyright © 2008 Scott Justis

Dean and Bailey (1961) studied the natural history of M. pruinosa in the Lower Rio Grande Valley, and summarized the findings of earlier works. In the area of Weslaco, Texas, this planthopper overwinters in the egg stage under bark and hatching begins in early March. Single eggs were scattered in the bark of dead citrus twigs. The first adults were found in the field about 69 days after the hatching date, and the were most abundant in June. There is one generation per year and adults may live several weeks. Nymphs feed on sap by piercing the bark or leaves with needle-like mouthparts and produce a sweet fluid called “honeydew”. A dryinid wasp parasite, Psilodryinus typhlocybae (Ashmead), commonly attacks nymphs of the citrus flatid planthopper and its relatives. P. typhlocybae is often cited as a potential biocontrol agent for M. pruinosa.

According to the University of Florida Institute of Food and Agricultural Sciences M. pruinosa occurs on some 40 kinds of plants, including citrus, orchard, and forest trees, grape and other vines, various shrubs, and some herbs (Wilson 1980). Economically important host plants include azaleas, basswood, black walnut, camellias, cherry laurel, corn, gooseberry, grape, grapefruit, hollies, magnolias, orange, pawpaw, peach, sassafras, seagrape, viburnum, and various species of ash, elm, maple, and oak. In general flatids do not cause real damage to the health of ornamental plants because they are typically not very abundant. In the rare chance that they do occur in high numbers they may cause damage by depositing large numbers of eggs under the bark. Also the waxy secretions and honeydew produced by the insects can benefit the growth of sooty molds, which disfigures plants and makes them unpleasant to touch. Fortunately, flatids are thought to transmit virus diseases only rarely (Wilson 1980).

M. pruinosa is found throughout North America, ranging from from Canada to Florida and Cuba and west to California. It is common in the Eastern United States, including North Carolina. Metcalf (1957) also listed reports from Cuba, Jamaica, Puerto Rico, and Bermuda. In 2003 the species was inadvertently introduced to Europe where it causes economic damage in some south European countries (Gudrun 2010).

• University of Florida Institute of Food and Agricultural Sciences

• North Carolina State University, North Carolina Cooperative Extension Service

• bug guide

• Dean HA, Bailey JC. 1961. A flatid planthopper, Metcalfa pruinosa. Journal of Economic Entomology 54: 1104-1106.

• Dozier HL. 1928. The Fulgoridae or plant-hoppers of Mississippi, including those of possible occurrence; a taxonomic, biological, ecological, and economic study. Technical Bulletin of the Mississippi Agricultural Experiment Station 14: 112-114.

• Metcalf ZP. 1923. J. Elisha Mitchell Science Society 38: 152.

• Metcalf ZP. 1957. General Catalog Homoptera, Fasc. 4, Part 13, Flatidae and Hypochthonellidae, 342-350.

• Metcalf ZP, Bruner SC. 1948. Cuban Flatidae with new species from adjacent regions. Annals of the Entomological Society of America 41: 96.

• Osborn, H. 1938. The Fulgoridae of Ohio. Bulletin of the Ohio Biological Survey 6: 318.

• Wene GP. 1950. The citrus fulgorid. Annual Proceedings of the Lower Rio Grande Valley Citrus and Vegetable Institute 4: 90-93.

• Wene GP, Riherd PT. 1954. Control of puss caterpillar and fulgorids attacking ornamentals during 1953. Texas Avocado Society Year Book for 1953: 45-46.

• C. H. Dietrich in Resh, V. H. & Carde, R. T. (eds.) 2003. Encyclopedia of Insects. Academic Press.