Brackish wasps

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Brackish wasps
Allurus lituratus

Allurus lituratus

Systematics
Class : Insects (Insecta)
Order : Hymenoptera (Hymenoptera)
Subordination : Waist Wasps (Apocrita)
Partial order : Legimmen (Terebrantia)
Superfamily : Similar parasitic wasps (Ichneumonoidea)
Family : Brackish wasps
Scientific name
Braconidae
Burmeister , 1829
Veins in the wings

The brackish wasps (Braconidae) are a family within the order of the hymenoptera . You belong to the Legims . Together with the Ichneumonidae , the parasitic wasps in the narrower sense, they form the superfamily of the Ichneumonoidea .

features

Brackish wasps are mostly small to medium-sized wasps with a very diverse body structure, which is varied in many forms in the various subfamilies. On average, they are smaller than the representatives of the Ichneumonidae, but they cannot be recognized because the size overlaps widely and there are some quite large species. As representatives of the superfamily Ichneumonoidea, they are most easily recognizable by the high number of antennae (at least 16, often much more) and the structure of the sternites on the free abdomen (metasoma or gaster). These always consist of a heavily sclerotized basal section and a slightly sclerotized, membranous posterior section; this is particularly characteristic of the first segment. Against the Aculeata they are z. B. also differentiable by the trochanter of the legs divided into two sections , this is what they have in common with most legims. A wing mark ( pterostigma ) is always formed in the wing . In addition, the anterior longitudinal veins in the forewing are all fused. A Costa cell is usually missing, if it is (rarely) present, it is extremely narrow. As a result, only two closed cells can be seen in the basal part of the fore wing. However, wingless species also occur in both families.

The differentiation of the Braconidae from the Ichneumonidae is not always easy. Above all, one feature in the wing veins is characteristic . Only in most Ichneumonidae is the cross vein 2m-cu formed in the distal rear section of the fore wing; in Braconidae it is absent. In the hind wing the cross vein branches off rs-m after the radius artery (Rs) has branched off from the fused longitudinal artery (CR-Rs), whereas in the Ichneumonidae this cross vein is attached to the fused vein before the branch. In numerous Braconidae (much less often in the Ichneumonidae) the wing veins are reduced, especially in the very small species. Wingless Ichneumonidae and Braconidae are not at all easily distinguishable, here the subfamily usually has to be determined.

Way of life

Brackish wasps are parasitoids because they parasitically feed on other insect larvae when they are young. Almost all members of the family develop inside their living and growing host (coinobionte endoparasitoids). Idiobiont parasitoids that paralyze or kill the host and then feed on it (usually as ectoparasitoids) occur, but are rare in the family (essentially: Doryctinae, Rogadinae and Braconinae). In many cases, however, the last larval stage leaves the host and continues to eat from the outside. In contrast to their sister family Ichneumonidae, there are very few hyperparasitoids (parasitoids of other parasitoids) to be found among brackish wasps. In fact, true hyperparasitoids are completely unknown, but there are some species that parasitize adult parasitic wasps (subfamily Euphorinae) or parasitize the hymenoptera larvae that have left their host to pupate (subfamily Meteorideinae). For the coinobiont parasitoids of growing hosts there is the problem of having to deal with the immune defense of their host. Similar to their sister family Ichneumonidae, brackish wasps of the subfamily Microgastrinae and some other (but not all) subfamilies also use symbiotic polydnaviruses that are given by the female when laying eggs. The viruses (known as Bracoviruses, belonging to the Polydnaviridae) only multiply in the wasp, not in the host. Here they form stable proviruses integrated into the genome . In the ovaries of the females, they replicate strongly and form numerous virions . If the host (usually a caterpillar) is bitten, the viruses are also applied. They infect the caterpillar's immune cells and suppress the immune system. Species of the subfamilies Agathidinae and some Aphidiinae pierce the ganglia of the nervous system when laying their eggs . Usually the eggs are laid in the body cavity ( haemocoel ) of the host. The eggs are usually very small, they swell significantly in the host through the absorption of liquid with nutrients. Numerous cells of the egg that do not belong to the embryo are released when the larva hatches and then continue to live and grow. These so-called teratocytes help feed the larvae. Possible other roles of the teratocytes (e.g. in immunosuppression) are suspected but have not been proven with certainty. Like many other parasitoids, many brackish wasps have a specialized first larval stage with enlarged, sickle-shaped mandibles and numerous appendages (e.g. tail threads) that increase mobility. This does not take up any food. Its task is to control other parasitoid larvae of the same or different species that it may encounter in the host.

The speed of development of most brackish wasp larvae of almost all subfamilies in the host can be exceptionally fast, so that all larval stages are passed through in a few days. The number of larval stages has only been determined in a few species and is often uncertain; three, four or five larval stages have been reported. The last (or penultimate) larval stage leaves for pupation usually the host. Like the intestines of all Apocrita, that of brackish wasp larvae is closed in front of the rectum until immediately before pupation, only now is the entire feces released as so-called meconium (it is rarely even held back until the imago hatches). Pupation takes place in a self-made web (exception: Opiinae, here without web). The Opiinae and some others do not pupate freely, but within the host. Groups in which numerous parasitoid larvae live in the same host (Gregärparasitoide) sometimes develop large joint pupation webs. In regions with winter cold, such as in Central Europe, most brackish wasps overwinter as adult larvae (or "prepupa") in the pupation web.

Hymenoptera as hosts are generally very rare in the family, they occur in the Ichneutinae and a few Doryctinae, Rogadinae and Braconinae. The species-rich subfamilies Opiinae and Alysiinae are parasitoids of fly maggots (suborder Cyclorrhapha ). Other common hosts are mainly beetle larvae and butterfly caterpillars, more rarely other orders such as reticulated winged (Neuroptera), grasshoppers, termites, beaked flies (Mecoptera). Locust larvae as hosts are extremely rare (so far only two species are known, one from Australia, the other from Malaysia), but so far only known among the Braconidae among the Hymenoptera. The subfamily Aphidiinae specializes in aphids, they are important antagonists of this group, which is often feared as pests in agriculture, and are therefore considered beneficial insects.

In some subgroups (for example the subfamily Cheloninae) the female lays her egg in the egg of its host, the hatching brackish wasp larva then eats in the hatched host larva. However, there are no real egg parasitoids (which already hatch from the host egg) in brackish wasps. The species of the subfamilies Neoneurinae, Euphorinae and numerous Aphidiinae are parasitoids of adult (imaginal) insects, the Aphidiinae of aphids, the Euphorinae in a large number of orders, but particularly often of beetles (Curculionidae, Chrysomelidae), the Neoneurinae in the abdomen of ants. Most of the other Braconidae parasitize their hosts' larvae, which they leave immediately, usually shortly before they pupate. Parasitoids that only hatch in the pupa stage of the host or direct parasitoids from pupae are rare among brackish wasps (few hatch from fly puparia).

Subfamilies with species (selection)

In the meantime over 12,000 species in approx. 1,000 genera and 45 subfamilies have been described, so it is estimated that there are between 40,000 and 50,000 species in total. This makes the brackish wasps one of the most species-rich insect families. In Europe the brackish wasps are represented with 33 subfamilies and over 3,300 species.

Web links

Commons : Braconidae  - collection of images, videos and audio files

Individual evidence

  1. ↑ Bruce A. Webb, Michael R. Strand, Stephanie E. Dickey, Markus H. Beck, Roland S. Hilgarth, Walter E. Barney, Kristy Kadash, Jeremy A. Kroemer, Karl G. Lindstrom, Walaikorn Rattanadechakul, Kent S. Shelby, Honglada Thoetkiattikul, Matthew W. Turnbull, R. Andrews Witherell (2006): Polydnavirus genomes reflect their dual roles as mutualists and pathogens. Virology 347 (1): 160-74.
  2. ↑ SRShaw (2004): Essay on the evolution of adult-parasitism in the subfamily Euphorinae (Hymenoptera, Braconidae). Proceedings of the Russian Entomological Society St. Petersburg 75 (1): 82-95.
  3. ↑ Braconidae. Fauna Europaea, accessed June 3, 2007 .