Whiteflies
| Whiteflies | ||||||||||||
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Greenhouse whitefly |
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| Systematics | ||||||||||||
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| Scientific name of the superfamily | ||||||||||||
| Aleyrodoidea | ||||||||||||
| Westwood, 1840 | ||||||||||||
| Scientific name of the family | ||||||||||||
| Aleyrodidae | ||||||||||||
| Westwood , 1840 |
The whale lice (Aleyrodoidea) are a superfamily of the plant lice (Sternorrhyncha) with the only family Aleyrodidae . Of the approximately 1500 species, 56 live in Europe and 17 in Central Europe. The body length of the animals is usually between 1 and 2 mm, the largest species (from tropical America) reach a body length of slightly more than 10 millimeters. All whiteflies feed on sap, and for this reason many species are considered pests in agriculture and horticulture.
Several species of whitefly are known as whitefly , including the greenhouse whitefly ( Trialeurodes vaporariorum ) and the ash whitefly ( Siphoninus phillyreae ).
features
The whiteflies are small, relatively soft-skinned, slightly sclerotized insects. They are separate sexes, females and males are of similar shape, mostly the males are somewhat smaller. The animals are yellowish, brownish or red in color. The body and wings of whiteflies are always covered with flour-like wax dust, which is excreted by the ventral abdominal glands, and appears white as a result. All species are winged, with fore and hind wings, the wings are crystal clear, with some species with dark spots or bands. The veining of the wings is greatly reduced. In the forewing, in addition to the marginal vein (costa) in the middle of the wing, there is only one conspicuous longitudinal vein that is straight in the subfamily Aleyrodinae and forked in the subfamily Aleyrodicinae. In the rear wing section, further veins (branches of the cubitus) can be present in some species.
The head is orthognathic, which means that the mouth opening is directed downwards. He wears large complex eyes, which in almost all species are either divided into an upper and a lower section or at least strongly constricted in the middle, the upper and lower eye sections have different spectral sensitivity at least in some species; they are used for orientation either in the illuminated sky (in the case of migrating individuals) or in the green vegetation (in the search for host plants). In addition, there are two single eyes ( ocelles ) close together . The mostly quite short, simply built antennas consist of seven segments in almost all species. The mouthparts are piercing and sucking and of the typical structure of the sternorrhyncha . The labium is four-segmented in whiteflies and can be extended and retracted telescopically by means of strong muscles; Extending the labium helps pull the piercing bristles out of the host plant.
On the trunk section, the front segment is short, while the middle and rear segments are roughly the same length. The legs are rod-shaped with elongated hips , the tarsi are two-segmented. At the end between the claws they have an unpaired, pillow-like structure called a paronychium, a transformed arolium that is used when holding onto smooth surfaces. The rear legs are reinforced and give the animals a certain jumping ability. Their rails have conspicuous bristle combs, which serve to distribute the wax deposited on the abdomen over the body. The abdomen is constricted at its base and therefore highly mobile. Its segments have glandular plates on the ventral side, from which the wax surrounding the body is deposited. In the Aleyrodinae there are four plates in the males, in the females two plates, in the Aleyrodicinae there are three or four plates. At the rear end of the abdomen, the females carry an ovipositor . The males have a copulation apparatus with an aedeagus and two grasping organs, which, however, can be strongly regressed in the Aleyrodinae.
In contrast to most insects, the species of whiteflies are not differentiated according to the imagines, which have not been well researched. The basis for the determination is the fourth larval stage called the pupa or puparium.
Life cycle
Reproduction is usually sexual, but sex determination is via arrhenotocia . Females are always formed from fertilized eggs, and males from unfertilized eggs ( haplodiploidy ). In most species, the sex ratio of females and males is about 1 to 1. The eggs of the animals are stalked, they are deposited by the female, often in rings, on the underside of leaves and are often covered with wax. The stem serves to absorb water. From them a first, freely moving larval stage hatches (also called nymph in the hemimetabolic insects ), which serves as the spreading stage ("crawler"). The following three larval stages are immobile and are stuck on the underside of the leaf. In many species they form a thick layer of wax reminiscent of that of scale insects , but some species also have nude nymphs. The nymphs have a pit on the upper side of the abdomen into which the anus opens, this has a lid (operculum) and a tongue-shaped projection called a ligula, which is used to throw away the separated honeydew so that the animal does not become stuck to it. The shape of these structures is very important in determining the species. The fourth larval stage forms so-called pupae towards the end of its development , in which the transformation into adult animals takes place. This pupal stage is not homologous to the pupa of the holometabolic insects .
Systematics of whiteflies
Two subfamilies are distinguished for the recent species:
- Subfamily Aleyrodinae Westwood
- Subfamily Aleyrodicinae Quaintance & Baker
Until recently, a third subfamily Udamoselinae Enderlein was listed for an aberrant genus Udamoselis ; this is not justified according to recent studies, the species is now assigned to the Aleyrodicinae.
Almost all whiteflies occurring in Central Europe belong to the subfamily Aleyrodinae, of the Aleyrodicinae only Paraleyrodes minei Iaccarino , 1990 from South America to Europe, the introduction of some other species is feared.
- Ash whitefly ( Siphoninus phillyreae )
- Greenhouse whitefly ( Trialeurodes vaporariorum )
- Tobacco whitefly (or tobacco whitefly) ( Bemisia tabaci )
- Kohlmottenschildlaus (or whitefly on carbon) ( Aleyrodes proletella )
- Citrus whitefly (or citrus whitefly) ( Dialeurodes citri )
- Woolly citrus moth scale ( Aleurothrixus floccosus )
other types:
Fossil whiteflies have been preserved as inclusions in amber, the group has been documented since the Cretaceous . Even the oldest fossil species are very similar in physique to the more recent ones. The group is particularly rich in individuals and species in Lebanon amber , but also occurs in Burmese amber from the Cretaceous period. Most fossil species have been assigned to an additional subfamily, Bernaeinae.
literature
- Bernhard Klausnitzer : Aleyrodina, whiteflies. In: Wilfried Westheide , Gunde Rieger (Ed.): Special Zoology. Part 1: Protozoa and invertebrates. Gustav Fischer, Stuttgart a. a. 1996, ISBN 3-437-20515-3 , pp. 655-656.
- Penny J. Gullan & Jon H. Martin: Sternorrhyncha (Jumping Plant-Lice, Whiteflies, Aphids, and Scale Insects). In: Vincent H. Resh, Ring T. Cardé: Encyclopedia of Insects. Academic Press, 2nd edition, 2009. ISBN 978-0-08-092090-0 . Page 957-967.
- Rolf G. Beutel, Frank Friedrich, Xing-Ke Yang, Si-Qin Ge: Insect Morphology and Phylogeny: A Textbook for Students of Entomology. Walter de Gruyter, Berlin 2014. ISBN 978-3-11-026404-3 . therein Chapter 6.22.2 Aleyrodina, Aleyrodoidea.
Individual evidence
- ^ A b Jon H. Martin & Laurence A. Mound (2007): An annotated check list of the world's whiteflies (Insecta: Hemiptera: Aleyrodidae). Zootaxa 1492: 1-84.
- ↑ a b Jon H. Martin (2007): Giant whiteflies (Sternorrhyncha, Aleyrodidae): a discussion of their taxonomic and evolutionary significance, with the description of a new species of Udamoselis Enderlein from Ecuador. Tijdschrift voor Entomologie 150: 13-29.
- ↑ Dimitry E. Shcherbakov (2000): The most primitive whiteflies (Hemiptera; Aleyrodidae; Bernaeinae subfam. Nov.) From the Mesozoic of Asia and Burmese amber, with an overview of Burmese amber hemipterans. Bulletin of the Natural History Museum London Geology 56 (1): 29-37.
