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HYMENOPTERA, Braconidae (Kirby 1837) -
(Ichneumonoidea). <Images-1> & <Images-2>
& <Images-3> & <Juveniles> Description & Statistics Braconidae. -- All species
of the braconids are parasitic on other insects. They sting the host and thereby paralyze it. There are more than 1850 North
American species most of which are beneficial. The adults are all fairly
small rarely exceeding 16 mm in long. Many are stout-bodied than the ichneumons, and the abdomen is
about as long as the head and the thorax combined. They are similar to ichneumonids by lacking a costal cell, but
they differ by not having more than one recurrent vein. Many species are valued as natural
controls of pest insects. Braconids and ichneumonids have
similar habits, but unlike the ichneumonids many pupate in silken cocoons on
the outside of the body of their hosts, while others spin silken cocoons
entirely apart from the host.
Polyembryony occurs in a few species, primarily in the genus Macrocentrus,
each egg of M. grandis Goidanich, a parasitoid of the European
corn borer, develops into from 16 to 24 larvae. This is a family of parasitoid
wasps and one of the richest families of insects. 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
ovipositors, 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. Most species are primary
parasitoids (both external and internal) on other insects, especially upon
the larval stages of Coleoptera, Diptera, and Lepidoptera, but also some
hemimetabolous insects like aphids, 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 host, such as the co-option of
endosymbiotic viruses for compromising host immune defenses. These
polydnaviruses 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.[1] 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 galls on
plants. Both syncitial and
holoblastic cleavage are present, even in closely related taxa. Larvae can be found on hosts as
diverse as aphids, bark beetles, and foliage-feeding caterpillars. Many
species are egg-larval parasitoids; hence they are often utilized as
biological pest control agents, especially against aphids. Natural History The family dates from early
Cretaceous (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 herbivores, the 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 labrum 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 clades that diverged
early in the evolution of braconids. The species Microplitis
croceipes possesses an extremely accurate sense of smell and can be
trained for use in narcotics and explosives detection. -------------------------------------------- References: Please refer to <biology.ref.htm>, [Additional references may be found
at: MELVYL Library] Basinger, G. 1938. The orange tortrix. Hilgardia 11: 661-63. Brown. 1946. Canad. Ent. 78:
121-29. Chiri, A. A. & E. F. Legner. 1982. Host-searching kairomones alter behavior
of Chelonus sp. nr. curvimaculatus, a hymenopterous parasite
of the pink bollworm, Pectinophora gossypiella (Saunders). Environ. Ent. 11: 452-55. Chiri, A. A. & E. F. Legner.
1983. Field applications of
host-searching kairomones to enhance parasitization of the pink bollworm
(Lepidoptera: Gelechiidae). J. Econ. Ent. 76: 254-255. Chiri, A. A. & E. F. Legner. 1986. Response of three Chelonus (Hymenoptera: Braconidae) species to kairomones in
scales of six Lepidoptera. Canad.
Ent. 118: 329-33. Crossman. 1922. USDA Bull 1028: 1-25. Davis. 1944. USDA Tech. Bull. 871: 1-19. Fallis. 1942. Canad. J. Res. Sect. D., Zool. Sci.
20: 13-19. Faure.
1926. Contrib. a l'étude de la
Piéride du Chon. Univ Lyon. p. 41-52. Fulton. 1940. Ann. Ent. Soc. Amer. 33: 240. Gilmore. 1938. J. Econ. Ent. 31: 712-15. Hamilton. 1935. Ent. Mon. Mag. 71: 262-70 Khandage, V. S., K. P. Pokhadkar & L. M. Nair. 1980.
Studies on the efficacy of Trichogramma
brasiliensis A. egg parasite and Apanteles angaleti M.
larval parasite in controlling cotton bollworms. Andhra Agr. J. 27:
41-2. Legner, E. F. & S. N. Thompson. 1977. Effects of the
parental host on host selection, reproductive potential, survival and
fecundity of the egg-larval parasitoid, Chelonus
sp. near curvimaculatus Cameron,
reared on Pectinophora gossypiella (Saunders) and Phthorimaea operculella (Zeller). Entomophaga 22: 75-84. Leius, G. 1960. Canad. Ent. 92: 371-75. Marsh, P. 1971.
Ann. Ent. Soc. Amer. 119:
33-78. Michelbacher & Smith. 1943. Factors limiting the alfalfa
butterfly. Hilgarida 15(4): 369-91. Muesebeck & Dohanian. 1917.
USDA Agr. Bull 1487: 1-34. Muesebeck. 1918. J. Agr. Res.
17: 191-206. Narayanan, E. S., B. R. Subha Rao &
G. A. Gangrade. 1956. beitr. Ent. 261-70. Narayanan, E. S., B. R. Subba Rao &
T. S. Thontadarya. 1962. Effect of
temperature and humidity on the rate of development of the immature stages of
Apanteles angaleti Muesebeck (Br., Hym.).
Proc. Nanth. Inst. Sci. India B-28: 156-63. Telenga, N. A. 1952. Origin and Evolution of Parasitism in
Hymenoptera Parasitica and Development of their Fauna in U.S.S.R. St. Publ.
109 p. Tothill. 1927. Canad. Dept. Agr. Tech. Bull.
(n.s.)3: 76-88. van Achterberg, C. 1976. Tijdschr. Ent. 119: 33-78. Worth, C. B. 1939. Obseervations on parasitism and
superparasitism (Lepid.: Sphingidae; Hymen.:Braconidae, Chalcididae). Ent. News 50: 137-41. Zwölfer, H. 1964. Notes on the parasites of Swammerdamia lutarea Hw. and S. caessella. Hb. (Lep. Hyponomentidae)
in Central Europe. Tech. Bull.
Commonw. Inst. Biol. Contr. 4:
121-46. |