|Crop Knowledge Master|
Nysius nemorivagus (White)
|A Lygaeid Bug|
Jayma L. Martin Kessing, Educational Specialist
Ronald F.L. Mau, Extension Entomologist
Department of Entomology
This species has been associated with both endemic and introduced plant species from sea level to over 13,000 feet (Beardsley, 1977). Crops attacked by this bug include: cabbage (all types), Chinese cabbage (Napa cabbage, won bok), cucumber, potato, and all types of squash. Holdaway (1944) considered this bug an occasional pest of Chinese cabbage and potatoes in higher elevations. Other host plants include Chenopodium oahuense (flower heads) (Beardsley, 1977), Clermontia, Dubautia, Lythrum (Zimmerman, 1948), Railliardia menziesii (Beardsley, 1966), Solana nodiflorum, and Sophora (Zimmerman, 1948). Several weeds are reservoir hosts of this bug, particularly those belonging to the Amaranthaceae, Chenopodiaceae, Compositae, Euphorbiaceae, and Portilacaceae families (Beardsley, 1979).
This bug is endemic to Hawaii and has been collected on Hawaii, Kauai, Lanai, Maui, and Molokai. They are most common in the drier portions of the islands (Beardsley, 1977).
Lygaeid bugs are primarily seed feeders, but adults may feed on flowers and foliage of various crops and ornamental plants (Beardsley, 1977).
These bugs can also be a nuisance pest. Large, flying aggregations of this insect have interfered with scientific studies conducted at observatories at the summit of Haleakala (Beardsley, 1966). In one particular incidence, insects flying between the path of a solar koronagraph and the sun caused a scattering of light from the wings and bodies of the insects that contaminated the data being collected. Nysius flight activity reduced the optimum period of use of this instrument by approximately 20% (Beardsley, 1966).
A description of the eggs or the duration of this stage was not found in the literature.
There are five nymphal stages, or instars, of this bug. This insect has a gradual metamorphosis, so the immature stages strongly resemble the adults and differ mainly in size and sexual maturity.
Lygaeid bugs have a narrowly oval or straight-sided body, about three times as long as wide and nearly an equilateral triangle in cross section (Metcalf, 1962). Body color varies from dark brown to black. The black head is moderately broad and short and has a brownish-yellow spot in the middle of the base and several pale stripes (Usinger, 1942). The dark antennae are attached low on the head. Lygaeid bugs, like other Hemipteran insects, have two pairs of wings. The front pair of wings is thickened and quite stiff at the basal half (called either the hemelytra or tegmen), and membranous at the tips (Metcalf, 1962). The hemelytra of this Nysius species is pale and mottled (Perkins, 1911). The second pair of wings are membranous. The membranous wings have four or five long veins that are usually not branched. At rest, the wings lay flat against the abdomen (Metcalf, 1962). The wings nearly cover the full width of the abdomen and exceed its length by one third the total length of the hemelytra (Usinger, 1942). Female Nysius bugs are larger and wider than the males (Beardsley, 1977). Males are about 1/8 inch (3.88 mm) long and 1/20 inch (1.31 mm) wide; Females are approximately 1/5 inch (5.33 mm) long and 1/12 inch (1.93 mm) wide (Usinger, 1942).
The dark antennae, pale mottled hemelytra, and black-spotted femora (upper segment of leg) of this Nysius species are conspicuous characters that distinguish this species from other Nysius species(Perkins, 1911). A detailed taxonomic description is given by Usinger (1942).
This bug, like other Nysius species, builds up unusually high populations on weeds. When overcrowding, lack of food, or drying up or removal of these weed hosts occurs, swarms of this insect may go into nearby crops and orchards where they may cause some damage (Zimmerman, 1948).
This species reproduces at lower elevations, then migrates to higher elevations, such as the summit of Haleakala, during the summer and fall (Beardsley, 1977).
Because this insect can build up large populations on several weed hosts, clean cultivation is very important in preventing damage caused by this insect. Particular attention should be given to removing amaranth, hairy horseweed, small-leaf horseweed and pig weed (Zimmerman, 1948).
Information on present day chemical control of this insect was not found in the literature.
Beardsley, J.W. Jr. 1966. Investigations of Nysius spp. and Other Insects at Haleakala, Maui During 1964 and 1965. Proc. Hawaiian Entomol. Soc. 29(2): 187-200.
Beardsley, J.W. Jr. 1977. The Nysius Seed Bugs of Haleakala National Park, Maui (Hemiptera: Lygaeidae: Orsillinae). Proc. Hawaiian Entomol. Soc. 22(3): 443-450.
Beardsley, J.W. Jr. 1979. Notes on Two Nysius Species Accidentally Introduced into Hawaii (Hemiptera: Lygaeidae: Orsillinae). Proc. Hawaiian Entomol. Soc. 23(1): 51-54.
Hirano, R.T. (Revisions and Additions). 1983. Handbook of Hawaiian Weeds, Second Edition (Eds. E.L. Haselwood and G.G. Motter). For Harold L. Lyon Arboretum by University of Hawaii press, Honolulu. 491 pages.
Holdaway, F.G. 1944. Insects of Vegetable Crops in Hawaii Today.
Proc. Hawaiian Entomol. Soc. 12(1): 59-80.
Metcalf, R.L. (Revised) 1962. Destructive and Useful Insects Their Habits and Control, Fourth Edition. (Earlier editions by C.L. Metcalf and W.P. Flint). McGraw-Hill Book Company; New York, San Francisco, Toronto, London. 1087 pages.
Perkins, R.C.L. 1911. Transactions of the Entomological Society of London. pp. 734.
Usinger, R.L. 1942. The Genus Nysius and It's Allies in the Hawaiian Islands (Hemiptera, Lygaeidae, Orsillini). Bernice P. Bishop Museum Bulletin. 173: 1-167.
Zimmerman, E.C. 1948. Nysius nemorivagus White. pp. 52, 104. In: Insects of Hawaii, Volume 3 Heteroptera. University of Hawaii Press, Honolulu. 255 pages.