Braconidae
Encyclopedia
Braconidae is a family of parasitoid
wasps and one of the richest families of insect
s. Between 50,000 and 150,000 species exist worldwide. The species are grouped into about 45 subfamilies and 1,000 genera, some important ones being: Ademon, Aphanta, Asobara, Bracon hebetor
, Cenocoelius
, Chaenusa, Chorebidea, Chorebidella, Chorebus, Cotesia, Dacnusa, Microgaster, Opius, Parapanteles, Phaenocarpa, Psenobolus.
The morphological variation among braconids is notable. Braconids are often black-brown (sometimes with reddish markings), though some species exhibit striking coloration and pattern, being parts of Müllerian mimicry complexes
. They have one or no recurrent veins, unlike other members of the Ichneumonoidea which usually have two. Wing venation patterns are also divergent to apparent randomness. The antennae
have 16 segments or more; the hind trochanters have 2 segments.
Females often have long ovipositor
s, an organ that largely varies intraspecifically. This variation is closely related to the host species upon which the wasp deposits its egg. Species that parasitize microlepidoptera
, for instance, have longer ovipositors, presumably to reach the caterpillar through layers of plant tissue. Some wasps also have long ovipositors because of caterpillar defense mechanisms such as spines or hairs.
s, especially upon the larval stages of Coleoptera, Diptera
, and Lepidoptera
, but also some hemimetabolous insects like aphid
s, Heteroptera
or Embiidina. Most species kill their hosts, though some cause the hosts to become sterile
and less active. Endoparasitoid species often display elaborate physiological adaptations to enhance larval survival within the host, such as the co-option of endosymbiotic viruses for compromising host immune defenses
. These polydnavirus
es are often used by the wasps instead of a venom cocktail. The DNA of the wasp actually contains portions that are the templates for the components of the viral particles and they are assembled in an organ in the female's abdomen known as the calyx. A 2009 study has traced the origins of these templates to a 100-million-year-old viral infection whose alterations to its host DNA provided the necessary basis for these virus-like "templates".
These viruses suppress the immune system and allow the parasitoid to grow inside the host undetected. The exact function and evolutionary history of these viruses are unknown. It is a little surprising to consider that sequences of polydnavirus genes show the possibility that venom-like proteins are expressed inside the host caterpillar. It appears that through evolutionary history the wasps have so highly modified these viruses that they appear unlike any other known viruses today. Because of this highly modified system of host immunosuppression
it is not surprising that there is a high level of parasitoid-host specificity. It is this specificity that makes Braconids a very powerful and important biological control agent.
Parasitism on adult insects (particularly on Hemiptera and Coleoptera) is also observed. Members of two subfamilies (Mesostoinae
and Doryctinae
) are known to form gall
s on plants.
and holoblastic cleavage are present, even in closely related taxa.
Larvae can be found on hosts as diverse as aphid
s, bark beetle
s, and foliage-feeding caterpillar
s. Many species are parasitoid
s that attack host eggs or larvae; hence they are often utilized as biological pest control
agents, especially against aphid
s.
(provided that Eobracon is properly assigned to this family). It underwent extensive diversification from mid or late Cretaceous
to early Tertiary
, correlating with the radiation of flowering plants and associated herbivore
s, the main hosts of braconids.
and the lower part of the clypeus
are concave with respect to the upper clypeus and the dorsal margin of the mandibles. These groups may be clade
s that diverged early in the evolution of braconids.
Ichneumonidae
by the following character combinations. In Braconidae, vein 2m-cu of the forewing is absent- this vein is present in 95% of Ichneumonidae. Vein 1/Rs+M of the forewing is 85% present in Braconidae but absent in all Ichneumonidae. Vein 1r-m of the hind wing is in 95% of Braconidae basal to the separation of R1 and Rs (it is opposite or apical in Ichneumonidae). In Braconidae Metasomal tergum 2 is fused with tergum 3, (secondarily flexible in Aphidiinae) - 90% of Ichneumonidae have a flexible suture.
possesses an extremely accurate sense of smell and can be trained for use in narcotics and explosives detection.
Braconidae are very resistant to ionizing radiation. While dose of only 4.5 Gy is sufficient to kill a average Human Braconidae can survive an exposure roughly 400x greater requiring ~1800 Gy.
On the University of Florida
/ Institute of Food and Agricultural Sciences
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Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
wasps and one of the richest families of insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s. Between 50,000 and 150,000 species exist worldwide. The species are grouped into about 45 subfamilies and 1,000 genera, some important ones being: Ademon, Aphanta, Asobara, Bracon hebetor
Bracon hebetor
Bracon hebetor is a minute Braconidae wasp that is an internal parasite to the caterpillar stage of Plodia interpunctella, the Indian meal moth, in the late larval stage of the Mediterranean flour moth and the almond moth....
, Cenocoelius
Cenocoelius
Cenocoelius is a genus of hymenopteran insects belonging to the family Braconidae. Those species whose life history has been studied are all koinobiont parasitoids on wood-boring beetle larvae ....
, Chaenusa, Chorebidea, Chorebidella, Chorebus, Cotesia, Dacnusa, Microgaster, Opius, Parapanteles, Phaenocarpa, Psenobolus.
Morphology
Müllerian mimicry
Müllerian mimicry is a natural phenomenon when two or more harmful species, that may or may not be closely related and share one or more common predators, have come to mimic each other's warning signals...
. They have one or no recurrent veins, unlike other members of the Ichneumonoidea which usually have two. Wing venation patterns are also divergent to apparent randomness. The antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
have 16 segments or more; the hind trochanters have 2 segments.
Females often have long ovipositor
Ovipositor
The ovipositor is an organ used by some animals for oviposition, i.e., the laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly...
s, an organ that largely varies intraspecifically. This variation is closely related to the host species upon which the wasp deposits its egg. Species that parasitize microlepidoptera
Microlepidoptera
Microlepidoptera is an artificial grouping of moth families, commonly known as the 'smaller moths' . These generally have a wingspan of under 20 mm, and are thus harder to identify by external phenotypic markings than macrolepidoptera...
, for instance, have longer ovipositors, presumably to reach the caterpillar through layers of plant tissue. Some wasps also have long ovipositors because of caterpillar defense mechanisms such as spines or hairs.
Parasitism
Most braconids are primary parasitoids (both external and internal) on other insectInsect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, especially upon the larval stages of Coleoptera, Diptera
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
, and Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
, but also some hemimetabolous insects like aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s, Heteroptera
Heteroptera
Heteroptera is a group of about 40,000 species of insects in the Hemiptera. Sometimes called "true bugs", that name more commonly refers to Hemiptera as a whole, and "typical bugs" might be used as a more unequivocal alternative since among the Hemiptera the heteropterans are most consistently and...
or Embiidina. Most species kill their hosts, though some cause the hosts to become sterile
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
and less active. Endoparasitoid species often display elaborate physiological adaptations to enhance larval survival within the host, such as the co-option of endosymbiotic viruses for compromising host immune defenses
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. These polydnavirus
Polydnavirus
The Polydnaviruses , are a family of insect viruses that contain two genera: Ichnoviruses and Bracoviruses . The ichnoviruses occur in ichneumonid wasps species and bracoviruses in braconid wasps. The genome of the virus is composed of multiple segments of double-stranded, superhelical DNA...
es are often used by the wasps instead of a venom cocktail. The DNA of the wasp actually contains portions that are the templates for the components of the viral particles and they are assembled in an organ in the female's abdomen known as the calyx. A 2009 study has traced the origins of these templates to a 100-million-year-old viral infection whose alterations to its host DNA provided the necessary basis for these virus-like "templates".
These viruses suppress the immune system and allow the parasitoid to grow inside the host undetected. The exact function and evolutionary history of these viruses are unknown. It is a little surprising to consider that sequences of polydnavirus genes show the possibility that venom-like proteins are expressed inside the host caterpillar. It appears that through evolutionary history the wasps have so highly modified these viruses that they appear unlike any other known viruses today. Because of this highly modified system of host immunosuppression
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
it is not surprising that there is a high level of parasitoid-host specificity. It is this specificity that makes Braconids a very powerful and important biological control agent.
Parasitism on adult insects (particularly on Hemiptera and Coleoptera) is also observed. Members of two subfamilies (Mesostoinae
Mesostoinae
The Mesostoinae, is a subfamily of wasps endemic to Australia.It contains four genera:* Andesipolis* Hydrangeocola* Mesostoa* Proavga...
and Doryctinae
Doryctinae
The Doryctinae or doryctine wasps are a large subfamily of braconid parasitic wasps with a worldwide distribution . Numerous genera and species formerly unknown to science are being described every year...
) are known to form gall
Gall
Galls or cecidia are outgrowths on the surface of lifeforms caused by invasion by other lifeforms, such as parasites or bacterial infection. Plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites...
s on plants.
Larval development
Surprisingly, both syncitialSyncytium
In biology, a syncytium is a large cell-like structure; filled with cytoplasm and containing many nuclei. Most cells in eukaryotic organisms have a single nucleus; syncytia are specialized forms used by various organisms.The term may also refer to cells that are connected by specialized membrane...
and holoblastic cleavage are present, even in closely related taxa.
Larvae can be found on hosts as diverse as aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s, bark beetle
Bark beetle
A bark beetle is one of approximately 220 genera with 6,000 species of beetles in the subfamily Scolytinae. Traditionally, this was considered a distinct family Scolytidae, but now it is understood that bark beetles are in fact very specialized members of the "true weevil" family...
s, and foliage-feeding caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s. Many species are parasitoid
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
s that attack host eggs or larvae; hence they are often utilized as biological pest control
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
agents, especially against aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s.
Natural history
The family seems to date from early CretaceousCretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
(provided that Eobracon is properly assigned to this family). It underwent extensive diversification from mid or late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
to early Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
, correlating with the radiation of flowering plants and associated herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s, the main hosts of braconids.
Classification
Braconidae is traditionally divided into more than 40 subfamilies. These fall to two major groups, informally called the cyclostomes and non-cyclostomes. In cyclostome braconids, the labrumLabrum (arthropod mouthpart)
The labrum is a flap-like structure that lies immediately in front of the mouth in almost all extant euarthropods, the general exception being provided by the probable chelicerate-relatives the pycnogonids. It has proved to be by far the most controversial of all arthropod head structures. It is...
and the lower part of the clypeus
Clypeus
The clypeus is one of the sclerites that makes up the "face" of an arthropod.In insects, the clypeus delimits the lower margin of the face, with the labrum articulated along the ventral margin of the clypeus. The mandibles bracket the labrum, but do not touch the clypeus. The dorsal margin of the...
are concave with respect to the upper clypeus and the dorsal margin of the mandibles. These groups may be clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s that diverged early in the evolution of braconids.
Differentiation from Ichneumonidae
Braconidae is distiguished from its sister groupCladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
Ichneumonidae
Ichneumonidae
Ichneumonidae is a family within the insect order Hymenoptera. Insects in this family are commonly called ichneumon wasps. Less exact terms are ichneumon flies , or scorpion wasps due to the extreme lengthening and curving of the abdomen...
by the following character combinations. In Braconidae, vein 2m-cu of the forewing is absent- this vein is present in 95% of Ichneumonidae. Vein 1/Rs+M of the forewing is 85% present in Braconidae but absent in all Ichneumonidae. Vein 1r-m of the hind wing is in 95% of Braconidae basal to the separation of R1 and Rs (it is opposite or apical in Ichneumonidae). In Braconidae Metasomal tergum 2 is fused with tergum 3, (secondarily flexible in Aphidiinae) - 90% of Ichneumonidae have a flexible suture.
Other characteristics
The species Microplitis croceipesMicroplitis croceipes
Microplitis croceipes is a braconid wasp native to Georgia. It is an important parasitoid of the caterpillars of Helicoverpa zea and of Heliothis virescens....
possesses an extremely accurate sense of smell and can be trained for use in narcotics and explosives detection.
Braconidae are very resistant to ionizing radiation. While dose of only 4.5 Gy is sufficient to kill a average Human Braconidae can survive an exposure roughly 400x greater requiring ~1800 Gy.
External links
- Tree of Life Braconidae
- University of Kentucky Key to subfamilies Johansen pdf
- EOL
- Agathidinae Synopsis Sharkey
- NNM Technical Bulletin Bibliography of Braconidae 1964-2003
- Checklist of British and Irish Braconidae pdf
- Achterberg C. van, C. O'Toole (1993) Annotated catalogue of the types of Braconidae (Hymenoptera) in the Oxford University Museum Zoologische VerhandelingenZoologische VerhandelingenZoologische Verhandelingen is a Dutch biology journal. It is published by the Rijksmuseum van Natuurlijke Historie in Leiden....
, Vol. 287 P. 1-43 PDF
On the University of Florida
University of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/ Institute of Food and Agricultural Sciences
Institute of Food and Agricultural Sciences
The University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
Featured Creatures website: