| Braconidae | |
|---|---|
 | |
| Atanycolus sp. | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Superfamily: | Ichneumonoidea |
| Family: | Braconidae Latreille, 1829 |
| Subfamilies | |
47, see text | |
| Synonyms | |
StenophasmidaeBenoit, 1949 | |
TheBraconidae are a family ofparasitoidwasps. After the closely relatedIchneumonidae, braconids make up the second-largest family in the orderHymenoptera, with about 17,000 recognized species and many thousands more undescribed.[1] One analysis estimated a total between 30,000 and 50,000, and another provided a narrower estimate between 42,000 and 43,000 species.[1]
The Braconidae are currently divided into about 47 subfamilies and over 1000 genera,[2] which includeAerophilus,Aleiodes,Apanteles,Asobara,Bracon,Cenocoelius,Chaenusa,Chorebus,Cotesia,Dacnusa,Diachasma,Dimeris,Microgaster,Opius,Parapanteles,Phaenocarpa,Spathius, andSyntretus.
These fall into two major groups, informally called the cyclostomes and noncyclostomes. In cyclostome braconids, thelabrum and the lower part of theclypeus are concave with respect to the upper clypeus and the dorsal margin of the mandibles. These groups may beclades that diverged early in the evolution of braconids.[3] Cyclostomes aremonophyletic whereas noncyclostomes can be divided formally into microgastroids, sigalphoids, helconoids, and euphoroids.[4]
The rare Australian subfamilyTrachypetinae was raised to family rank in 2020 (as "Trachypetidae"), but was reduced back to a subfamily in 2022.[5]
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The morphological variation among braconids is notable. They are often black-brown (sometimes with reddish markings), though some species exhibit striking coloration and patterns, being parts ofMüllerian mimicry complexes. They have one or no recurrent veins, unlike other members of the other family inIchneumonoidea (Ichneumonidae), which usually have two. Wingvenation patterns are otherwise highly variable. Theantennae typically have 16 segments or more; thetrochanters have two segments.
Females often have longovipositors, an organ that largely varies interspecifically. This variation is closely related to the host species upon which the wasp deposits its egg. Species that parasitizemicrolepidopterans, for instance, have longer ovipositors, presumably to reach the caterpillar through layers of plant tissue. Some wasps also have long ovipositors to bypass caterpillar defense mechanisms such as spines or hairs, or to reach deeply-burrowedColeoptera larvae in tree trunks.[6]
The larvae of most braconids are internal or externalprimary parasitoids of otherinsects, especially thelarval stages ofColeoptera,Diptera, andLepidoptera, but also somehemimetabolous insects such asaphids,Heteroptera, orEmbiidina. Most species kill their hosts, though some cause the hosts to becomesterile and less active. Parasitoidy on adult insects (particularly on Hemiptera and Coleoptera) also occurs. Members of two subfamilies, theMesostoinae andDoryctinae are known to formgalls on plants.[7][8] Braconids are often used asbiological pest control agents, especially against aphids.[9]
Thousands of species of insects are used as hosts by braconid wasps. A few notable examples are detailed here.
Some species of braconids are parasitoids ofOstrinia furnacalis (the Asian corn borer, a lepidopteran moth known for being a pest ofmaize in East Asia), theAfrican sugarcane borer (a moth commonly found in sub-Saharan Africa),[10] the butterflyDanaus chrysippus inGhana,[11] andLiriomyza trifolii (the American serpentine leafminer) andManduca quinquemaculata (the tomato hornworm) in North America.[12] Braconids often will prey on fruit fly larvae likeAnastrepha suspensa as well.[13]
Endoparasitoid species often display elaborate physiological adaptations to enhance larval survival within the host, such as the co-option ofendosymbiotic viruses for compromising hostimmune defenses. Thesebracoviruses are often used by the wasps instead of, or in addition to, 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.[14] 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".[15]
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. Sequences of polydnavirus genes show the possibility that venom-like proteins are expressed inside the host caterpillar. Through the evolutionary history of being used by the wasps, these viruses apparently have become so modified, they appear unlike any other known viruses today. Because of this highly modified system of hostimmunosuppression, a high level of parasitoid-host specificity is not surprising.
The family seems to date from earlyCretaceous (provided thatEobracon is properly assigned to this family). It underwent extensive diversification from mid or lateCretaceous to earlyCenozoic, correlating with the radiation of flowering plants and associated insectherbivores, the main hosts of braconids.
73 individual Braconidfossils of theKönigsberg Amber Collection were destroyed duringWorld War II as they were "stored in a salt-mine about 40 km fromGöttingen" with petrol. They were set on fire by theAllies.[16] This has arguably slowed the study of theevolution of the family.[17]
Braconids are distinguished from theirsister groupIchneumonidae by these character combinations. In Braconidae, vein 2m-cu of the forewing is absent except in the Chilean speciesApozyx penyai – 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.[18]
The speciesMicroplitis croceipes possesses an extremely accurate sense of smell and can be trained for use innarcotics andexplosives detection.[19]
At least some braconids appear to be very resistant toionizing radiation. While a dose of 400 to 1000rads can kill an average human, a dose of 180,000 rads was required to kill a braconid of genusHabrobracon in an experiment.[20]
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