Trichogrammatidae. -- Trichogrammatids are tiny insects, 0.3-1.1 mm long,. The three-segmented tarsi, and the microscopic hairs of the wings that are usually arranged in rows, distinguish them and the rather short head that is somewhat concave posteriorly. The members of this group are parasitoids attacking eggs of their hosts. Some species have been reared in large numbers to aid in the control of orchard pests.
Trichogrammatidae are tiny parasitic wasps with most species having adults less than 1.2 mm in length. They parasitize the eggs of many orders of insects and have been regarded as important biological control agents, attacking many pest insects particularly Lepidoptera.
These wasps are weak fliers and they may be dispersed by wind action. Their forewings are usually stubby, with a fringe of hinged setae around the outer margin to increase the surface area during the downstroke. The males of some species are apterous, and they may mate with their sisters inside the host egg email@example.comThis, dying without ever leaving the host egg. They are parasitic on the eggs of other insects. In order to complete development their adult size is never larger than a single host egg, and often multiple individuals will develop in a single egg making the emerging adults smaller than the host egg. The size varies from 0.22 – 1.55 mm.
Some such as Trichogramma are known to parasitize eggs of several insect orders, while other genera may be restricted to a single host order. The eggs of Hemiptera are parasitized by the largest number of genera (e.g. Aphelinoidea, Paracentrobia, and Ufens), though Coleoptera and Lepidoptera eggs are also utilized by some genera. Most species parasitize eggs placed in or on plant tissues. Several genera ( e.g. Hydrophylita, Lathromeroidea and Prestwichia) parasitize eggs of aquatic insects and have been reported to swim underwater in search of hosts.
Some genera of Trichogrammatidae have been deployed in biological control. Trichogramma spp. have received the most attention because they are parasitoids of pest Lepidoptera and can be mass propagated and released into the environment. Trichogramma has been widely used in augmentative biological control, and although the effectiveness of this technique has been documented in some European glasshouse experiments, convincing data is lacking as to its practicality for controlling pest insects in the open agroecosystem.
There are ca. 842 species in 84 genera worldwide. Species occur in all vegetated terrestrial habitats. Only two genera, Ittysella and Brachyufens, may be restricted to the Nearctic region. Six genera are found only in America (Brachista, Lathrogramma, Pintoa, Trichogrammatomyia, Xenufens, and Zagella). The family as been poorly sampled throughout the world and collections for comprehensive taxonomic studies are absent.
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