Schistocerca
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| Stål , 1873 |
Schistocerca is a genus of field locusts. The genus includes about 50 species. Some species belong to the group of migratory locusts and are feared agricultural pests. All species, with one exception, live in North and South America. The only species of the Old World, the desert locust , is the grasshopper that causes the most significant economic damage in the world.
features
They are medium-sized to large, usually relatively slim-built field locusts with a body length between 25 and 68 millimeters. The deck wings ( Tegmina ) are always long and almost parallel, they protrude far beyond the body and the hind knees in most species; all species are good fliers (hence bird grasshoppers). The coloring is extremely variable both between the species and within the species with red or yellow-brown, gray, yellow-green to green basic color with variable light and dark drawing elements, often a yellow stripe on the back that continues on the closed wings, and scattered dark spots the fore wings. Often different individuals, sometimes also different local populations of the same species, are colored very differently, so that coloring features should not be used for the determination. The head is rounded in profile and when viewed from above with a clear central keel. Some species have relatively long antennae for short-antenna terrors that are longer than the head and pronotum combined. Like all related groups, the animals have a distinctive, cone-shaped protrusion on their front breast (prosternum). The shape of the middle breast (mesosternum) is characteristic of the genus. This is drawn out laterally to the rear in a flap-like projection, which is always longer than wide in the species of the genus, and the inner edge of which is straight (not curved) delimited. In this way, the species can be distinguished, for example, from otherwise very similar, long-winged specimens of the genus Melanoplus .
The genital morphology, especially of the males, is important for determining the species and for differentiating from related genera. The shape of the subgenital plate is characteristic, it is drawn out at the end in two triangular shaped tips, the genus got its name from this feature (Greek schistos: "split" and kerkos "tail"). However, the shape of the Aedeagus is less species-specific than in many related genera and alone is not sufficient to determine the species.
The species can be identified using the online identification key from Hojun Song from the University of Central Florida.
Distribution and Biogeography
The species of the genus live, with one exception, in America. Nine species are known from Mexico, five from Florida and two from California. The exception is the desert locust Schistocerca gregaria with a large distribution area in Africa and South Asia.
The distribution pattern of the species, with one species in the Old World, has long been of interest to biogeographers. Here the hypothesis suggested that the African desert locusts descended from representatives from the American main distribution area, which crossed the Atlantic. The entomologist Vitaly Michailovitsh Dirsh, who conducts research in England, even synonymized the African species with the North American Schistocerca americana (a view that has not caught on). In October 1988 a swarm of desert locust locusts was actually registered that had crossed the Atlantic in flight - a flight distance of at least 5,000 kilometers non-stop. These animals flew in the opposite direction, from Africa to the Caribbean. A later study of the relationships with the methods of molecular phylogeny , based on homologous sections of the mtDNA , now showed that the desert locust of the Old World is the sister species of all American species taken together. It is thus almost certain that the American species must be traced back to one (or more) swarms of this species that had drifted in earlier times. This also makes it probable that the swarming behavior of the species has lost its original state and that it has been lost secondarily in the solitary species. A supporting indicator for this is that even solitary species, if kept in abnormally high density in the laboratory, develop characteristics of locusts, such as a striking red and black markings instead of green in the nymphs.
Migratory locusts
Within the genus, several species are known as migratory locusts , in addition to the desert locust Schistocerca gregaria , these are Schistocerca picifrons , Schistocerca cancellata and Schistocerca interrita (some authors also include Schistocerca americana among the migratory locusts, although the facts are not clear here). In these species, imagines and nymphs appear in two distinctly different forms in terms of coloration and various other morphological features and behavior. The nymphs of the solitary or solitary form are inconspicuous, mostly green, colored, those of the wandering or gregarious form have striking coloring and drawing patterns, often red or orange tones, combined with black; According to studies on the desert locust, this is a real warning : the nymphs of the migratory form eat more poisonous plants and are thus better protected against predators by secondary plant substances ingested with their food .
All migratory locust species are agricultural pests. Occasionally, however, solitary species of the genus are also harmful if they occur in particularly high densities, for example in citrus crops in Florida.
Taxonomy
The genus Schistocerca belongs to the subfamily Cyrtacanthacridinae of the family Acrididae (some taxonomists alternatively place it in a separate family Catantopidae with some related subfamilies). With one exception (the short-winged, flightless genus Halmenus , endemic to the Galapagos Islands ), this subfamily is only distributed in the Old World. The DNA investigation showed, however, that Schistocerca is paraphyletic compared to Halmenus , closely related to the Schistocerca species of the Galapagos Islands themselves. The species of this genus should therefore be included in the genus Schistocerca . According to the morphology and the results of molecular phylogeny, the genera Valanga , Nomadacris , Bryophyma and Rhadinacris are closely related .
use
In Mexico, species of the genus are prepared as food under the name Chapulines .
Individual evidence
- ↑ Hojun Song (2004): Revision of the Alutacea Group of Genus Schistocerca (Orthoptera: Acrididae: Cyrtacanthacridinae). Annals of the Entomological Society of America Vol.97, no.3: 420-436.
- ^ Theodore H. Hubbell (1960): The Sibling Species of the Alutacea Group of the Bird-Locust Genus Schistocerca (Orthoptera, Acrididae, Cyrtacanthacridinae). Miscellaneous Publications Museum of Zoology University of Michigan No.116. 91 pp. + plates.
- ↑ cf. Kathryn Kirk & Charles R. Bomar: Guide to the Grasshoppers of Wisconsin. Published by: Bureau of Integrated Science Services, Wisconsin Department of Natural Resources, 2005.
- ^ A b Schistocerca Information site, accessed by Hojun Song on July 14, 2014.
- ↑ Hojun Song (2009): Species-specificity of male genitalia is characterized by shape, size, and complexity. Insect Systematics & Evolution 40: 159-170.
- ↑ Hojun Song (2006): Description of Schistocerca cohni n. Sp. and redescription of S. socorro (Dirsh) (Orthoptera: Acrididae: Cyrtacanthacridinae) from Mexico. Zootaxa 1150: 43-52.
- ↑ John L. Capinera, Clay W. Scherer, Jason M. Sqitier: Grasshoppers of Florida. University of Florida, Institute of Agricultural Science, 1999 online
- ^ HF Strohecker, Woodrow W. Middlekauf, David C. Rent (1968): The Grasshoppers of California. Bulletin of the California Insect Survey Vol.10. 176 pp.
- ↑ Hojun Song (2004): On the origin of the desert locust Schistocerca gregaria (Forskal) (Orthoptera: Acrididae: Cyrtacanthacridinae). Proceedings of the Royal Society London Series B 271: 1641-1648 doi : 10.1098 / rspb.2004.2758
- ↑ a b N. R. Lovejoy, SP Mullen, GA Sword, RF Chapman, RG Harrison (2006): Ancient trans-Atlantic flight explains locust biogeography: molecular phylogenetics of Schistocerca. Proceedings of the Royal Society London Series B 273: 767-774 doi : 10.1098 / rspb.2005.3381
- ↑ Steven Gotham & Hojun Song (2013): Non-swarming grasshoppers exhibit density-dependent phenotypic plasticity reminiscent of swarming locusts. Journal of Insect Physiology 59: 1151-1159. doi : 10.1016 / j.jinsphys.2013.08.017
- ↑ Hojun Song (2011): Density-Dependent Phase Polyphenism in Nonmodel Locusts: A Minireview. Psyche Volume 2011, Article ID 741769, 16 pages. doi : 10.1155 / 2011/741769 (open access).
- ↑ Meir Paul Pener & Stephen J. Simpson (2009): Locust phase polyphenism: update on. Advances in Insect Physiology Vol. 39. Academic Press. ISBN 0123814286 Preview on Google Books
- ^ Gregory A Sword, Stephen J Simpson, Ould Taleb M El Hadi, Hans Wilps (2000): Density-dependent aposematism in the desert locust. Proceedings of the Royal Society London Series B vol. 267 no.1438: 63-68. doi : 10.1098 / rspb.2000.0967
- ^ MC Thomas (1991). The American grasshopper Schistocerca americana (Drury) (Orthoptera, Acrididae). Entomology Circular No.342. etited by. Florida Department of Agriculture and Consumer Services.
- ↑ Baoping Li, Zhiwei Liu, Zhe-Min Zheng (2011): Phylogeny and classification of the Catantopidae at the tribal level (Orthoptera, Acridoidea). ZooKeys 148: 209-255 doi : 10.3897 / zookeys.148.2081
