Locusta migratoria (Linnaeus)
Common name: Migratory locust.
Geographical distribution: Locusta migratoria occurs in all temperate and tropical parts of the Eastern Hemisphere, from the Canaries and the Azores in the West to Japan and New Zealand in the East. Commonwealth Institute of Entomology Map.
Host plants: This locust prefers gramineous plants, but may feed on a large variety of rangeland flora in its primary breeding sites, or on economic crops when present in the environment. Leguminous plants are less compatible nutritionally.
Morphology: The female is up to 90 mm in length, the male measures up to 65 mm. The mottled tegmina project beyond the end of the abdomen. Adults are grey-brown in color. The hindwings are transparent with a purplish cast, and a curved band of darker aspect runs diagonally across them. A dull yellow line runs dorsally along the crest of the pronotum.
Within this species in its broad distribution, solitariform adults are characterized by a concave pronotum. Their background coloration is cryptic, being green or brown, dependent on levels of ambient humidity. Gregariform adults are much darker. Isolated males are substantially larger than females whereas crowded males are similar to the females.
Life cycle: Within their vast geographic range the populations of the migratory locust show morphological and biological diversity, and the existence of nine subspecies is nowadays accepted; some are economic pests. Populations of L. migratoria that are endemic to temperate climates (some classified as subspecies), undergo embryonic diapause, establishing 1-2 annual generations. However, this does not occur in the subtropical Middle East. A non-swarming subspecies, L. m. cinerascens (Fabricius), exists in some of the other countries surrounding the Mediterranean.
As a rule, the migration of L. migratoria is more limited than that of the desert locust, Schistocerca gregaria (Forskal). Isolated migratory locusts fly at night, whereas crowded adults fly mainly by day. Isolated locusts have 1-2 more larval instars than individuals in crowded populations, but this does not prolong their development, which is more rapid than when crowded. In consequence locusts in crowded populations raise fewer generations.
The Israeli migratory locust population is similar to another population that is established in irrigated localities in central Arabia. Solitariform L. migratoria may occur in low numbers on field crops and grasses during summer and autumn in Israel, disappearing in winter.
Economic importance: At low population densities, the migratory locust is a minor pest. Although permanently Solitariform in the eastern Mediterranean, the behavior of occasional crowded populations is reminiscent of its gregariform subspecies, the African migratory locust, Locusta migratoria migratorioides (Reiche and Fairmaire), with which it can hybridize.
Management: Except on the rare occasions when the pest populations greatly increase, it does not require control measures. In its areas of abundance, environmentally compatible control agents, such as the entomopathogenic fungus Metarhizium flavoviride Gams & Rozsypal, applied in an oil-based formulation, have been tested. Insect growth regulators (IGRs) prevent normal molting.
A stamp depicting Locusta migratoria was produced in quatar (http://www.asahi-net.or.jp/~CH2M-NITU/qatare.htm).
Heifetz, Y., Applebaum, S.W., and Popov, G.B. 1994. Phase characteristics of the Israeli population of the migratory locust, Locusta migratoria (L.) (Orthoptera: Acrididae). Journal of Orthoptera Research 2: 15-20.
El-Minshawy, A.M., El-Hinnawy, N.H. et al. 1975. Population fluctuations of grasshoppers and locusts in Alexandria area (Egypt). Bulletin of the Entomological Society of Egypt 59: 83-98.
Sanyang, S. and van Emden, H.F. 1996. The combined effects of the fungus Metarhizium flavoviride Gams & Rozsypal and the insecticide cypermethrin on Locusta migratoria migratorioides (Reiche & Fairmaire) in the laboratory. International Journal of Pest Management 42: 183-187.
A stamp showing Locusta migratoria was issued in Qatar in 1998 (http://www.asahi-net.or.jp/~CH2M-NITU/qatare.htm).