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The Tachinidae are a large and variable family of true
flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
within the
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
order
Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
alone. Insects in this family commonly are called tachinid flies or simply tachinids. As far as is known, they all are
protelean Protelean organisms are widely regarded as a special class of parasites, often referred to as parasitoids. Protelean parasites refer to insects that begin the juvenile phase of their lives as parasites and ultimately destroy or consume their host t ...
parasitoids, or occasionally parasites, of
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
s, usually other insects. The family is known from many habitats in all zoogeographical regions and is especially diverse in South America.


Life cycle

Reproductive strategies vary greatly between Tachinid species, largely, but not always clearly, according to their respective life cycles. This means that they tend to be generalists rather than specialists. Comparatively few are restricted to a single host species, so there is little tendency towards the close co-evolution one finds in the adaptations of many specialist species to their hosts, such as are typical of protelean parasitoids among the
Hymenoptera Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
.
Larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...
e (
maggot A maggot is the larva of a fly (order Diptera); it is applied in particular to the larvae of Brachycera flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and crane flies. ...
s) of most members of this family are
parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
s (developing inside a living host, ultimately killing it). In contrast a few are
parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...
(not generally killing the host). Tachinid larvae feed on the host tissues, either after having been injected into the host by the parent, or penetrating the host from outside. Various species have different modes of
oviposition The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
and of host invasion. Typically, Tachinid larvae are
endoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s (internal parasites) of
caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...
s of butterflies and moths, or the
eruciform Eruciform (literally: "caterpillar-shaped") is the entomological term describing a certain class of shapes of insect larvae. Origin and application The word ''eruciform'' literally means "caterpillar-shaped" (from Latin "eruca", a caterpilla ...
larvae of
sawflies Sawflies are the insects of the suborder Symphyta within the order Hymenoptera, alongside ants, bees, and wasps. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay ...
. For example, they have been found to lay eggs in African sugarcane borer larva, a species of moth common in sub-Saharan Africa, as well as the more northerly Arctic woolly bear moth. However, some species attack adult
beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s and some attack beetle larvae. Others attack various types of
true bug Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to around ...
s, and others attack
grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...
s; a few even attack
centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
s. Also parasitised are bees, wasps and sawflies.


Oviposition and ovoviviparity

Probably the majority of female Tachinids lay white, ovoid eggs with flat undersides onto the skin of the host insect. Imms mentions the genera ''
Gymnosoma ''Gymnosoma'' is a genus of flies in the family Tachinidae. The name ''"Gymnosoma"'' literally translates as "naked body", and presumably refers to the fact that some species in the genus are less conspicuously bristly than most species of flies ...
'', ''Thrixion'', ''Winthemia'', and ''Eutachina'' as examples. In a closely related strategy some genera are effectively
ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...
(some authorities prefer the term ''ovolarviparous''Wood, D. M. 1987. Chapter 110. Tachinidae. Pp. 1193-1269 in McAlpine, J.F., Peterson, B.V., Shewell, G.E., Teskey, H.J., Vockeroth, J.R. and D.M. Wood (eds.), Manual of Nearctic Diptera. Volume 2. Agriculture Canada Monograph 28: i-vi, 675-1332.) and deposit a hatching larva onto the host. For example, this occurs in Tachinidae species which parasitize the butterfly ''
Danaus chrysippus ''Danaus chrysippus'', also known as the plain tiger, African queen, or African monarch, is a medium-sized butterfly widespread in Asia, Australia and Africa. It belongs to the Danainae subfamily of the brush-footed butterfly family Nymphalidae. ...
'' in Ghana. The free larvae immediately bore into the host's body. Illustrative genera include ''
Exorista ''Exorista '' is a genus of flies in the family Tachinidae. Subgenera & species *Subgenus ''Adenia'' Robineau-Desvoidy, 1863 **'' E. cuneata'' Herting, 1971 **'' E. mimula'' ( Meigen, 1824) **'' E. pseudorustica'' Chao, 1964 **'' E. rustica'' ...
'' and ''
Voria ''Voria'' is a genus of flies in the family Tachinidae. Species *'' Voria aurescens'' (Townsend, 1931) *'' Voria aurifrons'' (Townsend, 1892) *'' Voria capensis'' Villeneuve, 1935 *'' Voria ciliata'' d'Aguilar, 1957 *'' Voria erasmocoronadoi'' ...
''. Many Tachinid eggs hatch quickly, having partly developed inside the mother's uterus, which is long and often coiled for retaining developing eggs. However, it is suggested that the primitive state probably is to stick unembryonated eggs to the surface of the host. Many other species inject eggs into the host's body, using the extensible, penetrating part of their
ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
, sometimes called the oviscapt, which roughly translates to "egg digger". Species in the genera ''Ocyptera'', '' Alophora'', and ''
Compsilura ''Compsilura'' is a genus of tachinid flies in the family Tachinidae from Mozambique, Malawi and South Africa. Species *'' C. concinnata'' ( Meigen, 1824) *'' C. samoaensis'' Malloch, 1935 *'' C. solitaria'' ( Curran, 1940) *'' C. sumatrensis' ...
'' are examples. In many species only one egg is laid on or in any individual host, and accordingly such an egg tends to be large, as is typical for eggs laid in small numbers. They are large enough to be clearly visible if stuck onto the outside of the host, and they generally are so firmly stuck that eggs cannot be removed from the skin of the host without killing them. Furthermore, scientists have observed in studies with the host
cabbage looper The cabbage looper (''Trichoplusia ni'') is a medium-sized moth in the family Noctuidae, a family commonly referred to as owlet moths. Its common name comes from its preferred host plants and distinctive crawling behavior. Cruciferous vegetable ...
that being glued to the host insect helps maggots burrow into the larva, where they remain until fully developed. Yet another strategy of oviposition among some Tachinidae is to lay large numbers of small, darkly coloured eggs on the food plants of the host species. ''Sturmia'', ''Zenillia'', and ''
Gonia Gonia (Greek: ''Γωνιά'') is a village in the Rethymno regional unit in Crete, Greece, lying at an altitude of ca 222 m amsl, about 10 km southwest of the town of Rethymno Rethymno ( el, Ρέθυμνο, , also ''Rethimno'', ''Rethymnon ...
'' are such genera. Many Tachinids are important natural enemies of major insect pests, and some species actually are used in
biological pest control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
; for example, some species of Tachinid flies have been introduced into North America from their native lands as
biocontrol Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
s to suppress populations of alien pests. Conversely, certain tachinid flies that prey on useful insects are themselves considered as pests; they can present troublesome problems in the
sericulture Sericulture, or silk farming, is the cultivation of silkworms to produce silk. Although there are several commercial species of silkworms, ''Bombyx mori'' (the caterpillar of the domestic silkmoth) is the most widely used and intensively studie ...
industry by attacking
silkworm The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...
larvae. One particularly notorious silkworm pest is the Uzi fly ('' Exorista bombycis''). Another reproductive strategy is to leave the eggs in the host's environment; for example, the female might lay on leaves, where the host is likely to ingest them. Some tachinids that are parasitoids of stem-boring caterpillars deposit eggs outside the host's burrow, letting the first
instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...
larvae do the work of finding the host for themselves. In other species, the maggots use an ambush technique, waiting for the host to pass and then attacking it and burrowing into its body. Adult Tachinids are not parasitic, but either do not feed at all or visit flowers, decaying matter, or similar sources of energy to sustain themselves until they have concluded their procreative activities. Their non-parasitic behaviour after eclosion from the pupa is what justifies the application of the term "protelean".


Description

Tachinid flies are extremely varied in appearance. Some adult flies may be brilliantly colored and resemble blow-flies (family
Calliphoridae The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ba ...
). Most however are rather drab, some resembling house flies. However, Tachinid flies commonly are more bristly and more robust. Also, they usually have a characteristic appearance. They have three-segmented antennae, a diagnostically prominent postscutellum bulging beneath the scutellum (a segment of the
mesonotum The mesothorax is the middle of the three segments of the thorax of hexapods, and bears the second pair of legs. Its principal sclerites (exoskeletal plates) are the mesonotum (dorsal), the mesosternum (ventral), and the mesopleuron (lateral) on ...
). They are aristate flies, and the arista usually is bare, though sometimes plumose. The
calypter A calypter is either of two posterior lobes of the posterior margin of the forewing of flies between the extreme posterior wing base and the alula, which covers the halteres. The lower calypter is the proximal calypter (synonyms: squama (of som ...
s (small flaps above the
halteres ''Halteres'' (; singular ''halter'' or ''haltere'') (from grc, ἁλτῆρες, weights held in the hands to give an impetus in leaping) are a pair of small club-shaped organs on the body of two orders of flying insects that provide infor ...
) are usually very large. Their fourth long vein bends away sharply. Adult flies feed on
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s and
nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...
from
aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s and
scale insect Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...
s. As many species typically feed on
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
, they can be important
pollinator A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains. Insects are the maj ...
s of some plants, especially at higher elevations in mountains where bees are relatively few. The
taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
of this family presents many difficulties. It is largely based on morphological characters of the adult flies, but also on reproductive habits and on the immature stage.


As biological pest control

Some tachinid flies parasitize pest species. This has allowed them to be used as
biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
agents by farmers. Some Tachinidae are generalists; for instance, ''
Compsilura concinnata ''Compsilura concinnata'' ( tachinid fly; order Diptera) is a parasitoid native to Europe that was introduced to North America in 1906 to control the population of an exotic forest, univoltine, spongy moth named ''Lymantria dispar''. It is an e ...
'' uses, at least, 200 different hosts, and they are not safe to be used as biological controls. Others are more specialized and are safer; for instance, '' Istocheta aldrichi'', which only attacks the
Japanese beetle The Japanese beetle (''Popillia japonica'') is a species of scarab beetle. The adult measures in length and in width, has iridescent copper-colored elytra and a green thorax and head. It is not very destructive in Japan (where it is control ...
.


Evolution

This clade appears to have originated in the middle
Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
. The oldest known putatively tachinid fossil ('' Lithexorista'') dates from the Eocene
Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...
in
Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...
.C. H. T. Townsend. 1921. Some new muscoid genera ancient and recent. ''Insectur Inscitiae Menstruus'' 9:132-134


See also

* List of Tachinidae genera *
Parasitoid wasp Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causin ...


References


External links


Australasian/Oceanian Diptera Catalog



Bugguide.net: North American Tachinidae

Diptera.info



''Handbooks for the Identification of British Insects, Vol. X. Part 4(a): Diptera CyclorrhaphaCalyptrata (I) Section (a). Tachinidae and Calliphoridae'' (1st portion)(2nd portion)
by F.I. van Emden (1954), Royal Entomological Society of London




''Rhinophorids - when a tachinid isn't a tachinid!''




diagnostic photographs of 8 species by Cirrus Digital Imaging

J. E. O'Hara, North American Dipterists Society
''The Siphonini (Diptera: Tachinidae) of Europe'' (preview)
by Stig Andersen (1996)
UK Tachinid Recording Scheme

Stireman, J. TACHINIDAE: Evolution, Behavior, and Ecology
{{Taxonbar, from=Q235715 Insects used as insect pest control agents Diptera used as pest control agents Brachycera families