| Cecidomyiidae | |
|---|---|
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Suborder: | Nematocera |
| Infraorder: | Bibionomorpha |
| Superfamily: | Sciaroidea |
| Family: | Cecidomyiidae Newman, 1835 |
| Subfamilies | |
| Synonyms | |
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Cecidomyiidae is a family offlies known asgall midges orgall gnats. As the name implies, thelarvae of most gall midges feed withinplant tissue, creating abnormal plant growths calledgalls. Cecidomyiidae are very fragile small insects usually only 2–3 mm (0.079–0.118 in) in length; many are less than 1 mm (0.039 in) long. They are characterised by hairy wings, unusual in theorderDiptera, and have longantennae. Some Cecidomyiids are also known for the strange phenomenon ofpaedogenesis in which the larval stage reproduces without maturing first.[4][5] In some species, the daughter larvae consume the mother, while in others, reproduction occurs later on in the egg or pupa.[5]
More than 6,650species and 830genera are described worldwide, though this is certainly an underestimate of the actual diversity of this family.[6] ADNA metabarcoding study published in 2016 estimated the fauna ofCanada alone to be in excess of 16,000 species, hinting at a staggering global count of over 1 million cecidomyiid species that have yet to be described, which would make it the most speciose single family in the entire animal kingdom.[7] A second similar metabarcoding study performed in Costa Rica also found Cecidomyiidae to be the most diverse family of flies, supporting this assertion.[8] A third metabarcoding study in 2023 concluded that Cecidomyiidae are the single most diverse family collected frommalaise traps all around the world and are a dominant component of insect diversity, comprising about 20% of all species collected.[9]
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Cecidomyiidae are minute to small (0.5–3.0 mm), rarely larger (up to 8 mm, wing length 15 mm) flies with a delicate appearance. Except for a few genera with reduced wings, the eyes areholoptic. The mouthparts are reduced. Cecidomyiidantennae are notably long, with 12–14 segments, (sometimes fewer and up to 40 in some genera). The antennal segments either consist of a basal thickening andpetiole or they are binodal, with a proximal node, an intermediate petiole and a distal node. Basal, medial, and apical whorls of hairs occur on the antennal segments. In some species, whorls of loop-shaped sensory filaments are also found, the basal or medial one sometimes being reduced. Some gall flies have only one (basal) whorl of hairs on the antennal segments, and the sensoria (transparent sensory appendages) differ in size and shape. The filaments are thread-like in thePorricondylinae and in all the Cecidomyiinae and take the form of long loops in the supertribe Cecidomyiidi).Ocelli are present only in theLestremiinae. The wings are usually clear, rarely patterned. The wing bearsmicrotrichia, often as scales, and some species have macrotrichia. The number of longitudinal veins is reduced. Onlyveins R1, R4+5, M3+4 and Cu1 are well developed in most species. The medial veins M1 and M2 are developed only in primitive groups, and the costa usually has a break just beyond vein R5. The legs are long and slender, without apical bristles. Gall midge larvae, and many adults, are orange or yellow in color due tocarotenoids.[10] Cecidomyiidae are among the very few animals which can synthesize carotenoids, but its unknown to what degreede novo biosynthesis of carotenoids accounts for their characteristic color as opposed to dietary sequestration or endosymbionts.[11] The genes responsible for carotenoid synthesis likely originate fromhorizontal gene transfer from a fungal donor.[11]
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The genitalia of males consist of gonocoxites, gonostyles, aedeagus, and tergites 9 and 10. Lower (in the evolutionary sense) gall flies often have sclerotized parameres and a more or less transparent plate (the tegmen) located above theaedeagus-the tegmen. In higher gall flies, the parameres and tegmen are not developed. In these, instead, close to the aedeagus, is a triangular basal outgrowth of the gonocoxites called the gonosterna. Supporting structures called apodema are located near the base of the genitalia in males; these are often equipped with two outgrowths. The ovipositor is short, lamelliform, or long, mobile, and in some species, acicular.
The larva is peripneustic. The head is tiny, cone-shaped, and has two posterolateral extensions. The mouthparts are reduced, with minute styliform mandibles. The relatively prominent antennae are two-segmented. Integumental setae or papillae are important in taxonomy since they are constant in number within groups. The prothorax has sclerotized sternal spatula (most). The anus is terminal in the Lestremiinae and paedogenetic in the Porricondylinae and ventral in other groups. The pupa is exarate (in a few species it is enclosed within the last instar larval integument). The anterior spiracle and anterior angle of antennal bases is prominent (most).[12][13]
Many species are economically significant, especially theHessian fly, a wheat pest, as the galls cause severe damage. Other important pests of this family are the wheat blossom midgeSitodiplosis mosellana, theAsian rice gall midge (Orseolia oryzae) and theAfrican rice gall midgeO. oryzivora. The millet grain midge (Geromyia penniseti), sorghum midge (Contarinia sorghicola), and African rice gall midge (Orseolia oryzivora) attack grain crops such aspearl millet inMali and other countries of theSahel in West Africa.[14]
Other pests are thecoffee flower midge (Dasyneura coffeae),Soybean pod gall midge, (Asphondylia yushimai)pine needle gall midge (Thecodiplosis japonensis), thelentil flower midge (Contarinia lentis), thelucerne flower midge (C. medicaginis), and thealfalfa sprout midge (Dasineura ignorata) on the Leguminosae; theblack locust tree gall midge (Obolodiplosis robiniae), theswede midge (Contarinia nasturtii), and the brassica pod midge (Dasineura brassicae) on theCruciferae; thepear midge (Contarinia pyrivora) and theraspberry cane midge (Resseliella theobaldi) on fruit crops;Horidiplosis ficifolii on ornamental figs, and the rosette gall midge (Rhopalomyia solidaginis) ongoldenrod stalks, Porricondylini spp. onCitrus,Lestremia spp. on sweet potato, yam, ginger, garlic, onions, taro tubers, and potato,Lestodiplosis spp.,Acaroletes spp., andAphidoletes spp. on oranges, andArthrocnodax spp. on limes.[15][16][17]
In South Africa,Dasineura rubiformis has been deployed against the invasive AustralianAcacia mearnsii; it oviposits eggs into the flowers which develop into galls, thus reducing seed production.[18]
Parasitoids hosted by Cecidomyiidae includeBraconidae (Opiinae, Euphorinae),Eurytomidae,Eulophidae,Torymidae,Pteromalidae,Eupelmidae,Trichogrammatidae, andAphelinidae. All contain species which are actual or potential biological agents.
A large number of gall midge species are natural enemies of other crop pests. Their larvae arepredatory, and some are reported asparasitic. The most common prey areaphids andspider mites, followed byscale insects, then other small prey such aswhiteflies andthrips, which eat the eggs of other insects or mites. As thelarvae are incapable of moving considerable distances, a substantial population of prey must be present before the adults lay eggs, and the Cecidiomyiidae are most frequently seen during pest outbreaks. One species,Aphidoletes aphidimyza, is an important component ofbiological control programs for greenhouse crops and is widely sold in theUnited States.
