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from Wikipedia

Midges
A biting midge feeding on blood through an artificial membrane for insect rearing
A biting midge feeding on blood through an artificial membrane for insect rearing
Scientific classificationEdit this classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Suborder: Nematocera
Families

See text

A midge is any small fly, including species in several families of non-mosquito nematoceran Diptera. Midges are found (seasonally or otherwise) on practically every land area outside permanently arid deserts and the frigid zones. Some midges, such as many Phlebotominae (sand fly) and Simuliidae (black fly), are vectors of various diseases. Many others play useful roles as prey for insectivores, such as various frogs and swallows. Others are important as detritivores, and form part of various nutrient cycles. The habits of midges vary greatly from species to species, though within any given family midges commonly have similar ecological roles.

Examples of families that include species of midges include:[1]

Examples

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The Ceratopogonidae (biting midges) include serious blood-sucking pests, feeding both on humans and other mammals. Some of them spread the livestock diseases known as blue tongue and African horse sickness – other species though, are at least partly nectar feeders, and some even suck insect bodily fluids.[8]

Many midges are known for having symbiotic relationships with many other organisms. These can be commensal, parasitic or mutualistic relationships. Many of the commensal relationships are found within the family Chironomidae.[9]

A midge of the family Ceratopogonidae (lower middle - a branch is its background) sitting on a mantis sucking its hemolymph whilst the mantis feeds on a bee

Other ceratopogonid midges are major pollinators of Theobroma cacao (cocoa tree). Having natural pollinators has beneficial effects in both agricultural and biological products because it increases crop yield and also density of predators of the midges (still beneficial to all parties).[10]

The term "midge" is a vague term that refers to a large and diverse group of organisms. Although many are known as "bloodsuckers," there are many different roles that they play in their respective ecosystems.[9] There is, for example, no objective basis for excluding the Psychodidae from the list, and some of them (or midge-like taxa commonly included in the family, such as Phlebotomus) are blood-sucking pests and disease vectors.

Most midges, apart from the gall midges (Cecidomyiidae), are aquatic during the larval stage. Some Cecidomyiidae (e.g., the Hessian fly) are considered significant pests of some plant species. The larvae of some Chironomidae contain hemoglobin and are sometimes referred to as bloodworms.[11]

Non-biting midge flies are commonly considered a minor nuisance around bodies of water.[12] In May 2025, a large emergence of midges caused mayhem at the World Exposition in Osaka, Japan.[13]

See also

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References

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Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
A midge is a tiny dipteran fly, typically measuring 1–3 mm in length, belonging to various families within the suborder of the order Diptera, such as the non-biting and the biting . Unlike mosquitoes, most midges lack specialized piercing mouthparts for blood-feeding, though certain species in the family, known as biting midges or no-see-ums, can inflict painful bites on humans and animals. These insects are abundant worldwide, often swarming in large numbers near aquatic environments where their larvae develop. Midges exhibit complete , with aquatic larvae that serve as important decomposers in freshwater ecosystems by feeding on organic , , and , thereby nutrients. Adult midges, which live only a few days to weeks, do not bite in the case of chironomids but contribute to food webs as prey for , birds, bats, and predatory like dragonflies. Biting midges, in contrast, are vectors for diseases such as bluetongue in and Oropouche virus in humans, making them significant in veterinary and contexts. Notable examples include the ( impunctatus), a prevalent in that forms dense swarms and causes substantial irritation to humans and during summer months. Gall midges in the family induce plant as larvae, influencing by damaging crops like soybeans and canola. Overall, midges are ecologically vital despite their nuisance status, supporting through their roles in nutrient cycling and as a foundational food source in both aquatic and terrestrial habitats.

Overview

Definition

A midge is any small belonging to several families within the non-mosquito nematoceran suborder of Diptera, typically measuring 1–3 mm in length. These are characterized by their delicate bodies and two wings, distinguishing them from other fly groups, and they encompass both and non-biting species found worldwide, including polar regions, but generally absent from permanently arid environments. The term "midge" originates from myċġ or mycge, referring to small gnats or flies, derived from Proto-Germanic roots denoting diminutive flying insects. This etymology reflects its long-standing use to describe tiny, often annoying aerial pests in English-speaking regions. Midges differ from mosquitoes, which are also nematocerans but possess specialized piercing-sucking mouthparts for blood-feeding in females, whereas most midges—especially non-biting forms—lack such proboscises and instead have simpler mouthparts for or consumption. Additionally, midges exhibit distinct wing venation patterns, with shorter wings that do not extend beyond the body, unlike the longer, scaled wings of mosquitoes. Male midges often have hairy, plumose antennae. Common names for midges vary by type and region; for instance, midges are often called "no-see-ums" due to their minuscule size, while non- chironomid midges are known as "lake flies" in areas near water bodies where they swarm.

Distinguishing Features

Midges are distinguished from other small flies, such as , primarily by their wing characteristics; they possess a single pair of membranous wings lacking scales, in contrast to the scaled wings of , with venation patterns that are diagnostic for identification within the group. At rest, these wings are typically held flat or in a roof-like position over the , differing from the angled posture of wings. This structure contributes to their delicate appearance and weak flight capabilities. The body of midges is notably slender, featuring a long, cylindrical and elongated legs that are often disproportionate to their overall small size of 1–3 mm. Antennae exhibit pronounced : males have plumose, feathery antennae adapted for detecting pheromones or the high-pitched sounds produced by female wings during courtship, while females possess filiform, thread-like antennae with fewer sensory structures. Non-biting midges, in particular, have reduced mouthparts incapable of piercing , lacking the elongated seen in biting species or mosquitoes. Midges display unique behavioral traits in flight, acting as weak fliers that form dense, stationary swarms, predominantly of males, especially at to attract females for . These swarms enable coordinated movement through sensory adaptations, including large compound eyes that facilitate detection of motion and light within the group, aiding in maintaining swarm cohesion without direct physical contact.

Taxonomy and Classification

Major Families

Midges belong to several families within the order Diptera, collectively encompassing over 20,000 described species worldwide as of 2025. These families are primarily classified under the suborder , characterized by their small size and diverse ecological roles, though the focus here is on taxonomic distinctions. The , known as non-biting midges, represent the largest family with approximately 10,000 described species. Key diagnostic traits include adults with plumose antennae in males, short palps, and wings lacking scales, distinguishing them from similar flies like mosquitoes. Larvae are predominantly aquatic, often inhabiting freshwater sediments or constructing silken tubes. The , or biting midges, comprise about 6,200 extant . Adults are small (1–3 mm), with females featuring a well-developed for blood-feeding; wings are broader than in , often with distinctive patterns, and typically held flat over the at rest. Larvae are semi-aquatic or terrestrial, frequenting moist soils or decaying . Among other notable families, the (gall midges) include roughly 6,600 described species. Diagnostic features encompass very fragile bodies (often under 2 mm), reduced wing venation, and males with long, beaded antennae; many species induce plant , where larvae develop.

Evolutionary History

The fossil record of midges, encompassing both non-biting () and biting () forms, extends back to the period. The earliest known chironomid fossil, Aenne triassica, originates from Late deposits in , dating to approximately 205–201 million years ago, marking the oldest definitive record of the family. Chironomid fossils become more diverse and abundant by the period, with numerous specimens preserved in and sedimentary rocks, reflecting increased ecological roles in freshwater systems. In contrast, the Ceratopogonidae fossil record begins later, with the oldest described species, Archiaustroconops besti, from Early Purbeck Limestone deposits in southern , approximately 142 million years old. This disparity highlights an incomplete pre- record for biting midges, with few transitional forms documented, underscoring the need for expanded paleogenomic analyses to recover and clarify early divergences. Phylogenetically, midges occupy basal positions within the paraphyletic suborder of Diptera. Non-biting midges () form the superfamily Chironomoidea, while biting midges () belong to Culicomorpha, a that also includes mosquitoes (Culicidae) and black flies (Simuliidae). Recent phylogenomic studies position Chironomoidea as the to Culicomorpha, supporting a close evolutionary relationship between non-biting midges and the mosquito-inclusive lineage. A hallmark in this lineage is the aquatic larval stage of chironomids, often featuring hemoglobin-rich that facilitates respiration in oxygen-depleted sediments, an innovation likely predating the diversification and enabling exploitation of hypoxic freshwater niches. The major radiation of midges occurred during the era, coinciding with the diversification of angiosperms around 140–100 million years ago in the Early to mid-Cretaceous. This plant radiation expanded riparian and lacustrine habitats, providing novel breeding sites and food resources that drove midge proliferation, particularly for aquatic larvae dependent on organic-rich sediments. Post-2020 genetic research, leveraging of the COI gene, has illuminated ongoing evolutionary dynamics by uncovering cryptic species complexes—undescribed lineages indistinguishable morphologically but genetically distinct—in both families. For instance, studies on biting midges have identified multiple cryptic taxa across regions, enhancing resolution of patterns. These analyses also affirm the of key subfamilies like Chironominae and Ceratopogoninae, reinforcing the stability of higher-level classifications while highlighting gaps in fossil integration for deeper time scales.

Biology

Morphology

Midges, belonging to the families (non-biting midges) and (biting midges), exhibit delicate, slender typical of nematoceran Diptera, with body lengths ranging from 1 to 10 mm depending on the species and family. The adult head features prominent compound eyes and antennae that show marked : males possess bushy, plumose antennae adapted for detecting pheromones, while females have simpler, whorled or filiform antennae. The varies significantly between families; in , it is short and non-piercing, suited for feeding, whereas in female , it is elongated and equipped with piercing stylets for blood-feeding. The is robust relative to the body size, bearing three pairs of long, slender legs each with five segments (coxa, , , , tarsus) terminating in claws, and a pair of —small, club-shaped organs that function in flight balance. The abdomen is segmented and flexible, typically ending in cerci in females, which are paired appendages associated with the used for egg deposition. Larval midges are generally worm-like and aquatic or semi-aquatic, lacking true jointed legs but often featuring for locomotion. They possess a distinct, sclerotized head capsule with mouthparts adapted for filter-feeding or scraping, and the body is elongate with up to 12 segments. In , many larvae are known as bloodworms due to their red coloration from , which enables survival in low-oxygen environments such as profundal lake sediments; these larvae typically have a single fleshy at the anterior and posterior ends. Ceratopogonid larvae share a similar vermiform shape but often have the head capsule more protrusible and are predaceous or detritivorous. The pupal stage is comma-shaped, with the head and thorax fused into a and the abdomen curved ventrally, facilitating emergence from breeding habitats. A key feature is the pair of thoracic respiratory horns, which are tubular structures with apertures allowing at the substrate surface; these horns vary in length and branching but are essential for oxygenation during the brief pupal period. This morphology is conserved across both families, though Ceratopogonid pupae may have more ornate horn structures in some genera. At the microscopic level, midge wings lack scales, distinguishing them from moths (), and instead bear fine setae or hairs, particularly dense in ; wing venation is reduced with few prominent veins, aiding in taxonomic identification.

Life Cycle

Midges undergo complete (holometabolous) , consisting of , larval, pupal, and stages. Female midges lay eggs in gelatinous masses on surfaces or moist , with each mass containing hundreds to thousands of eggs depending on the . These eggs typically hatch within 2-7 days, influenced by and oxygen levels. The larval stage comprises four instars, during which midges are primarily aquatic or in moist environments, feeding on , , and microorganisms; some possess hemoglobin in their hemolymph to aid respiration in low-oxygen conditions. This stage lasts 1-3 weeks under optimal temperatures, though it can extend longer in cooler conditions. The pupal stage is non-feeding and transitional, lasting 1-4 days, after which the pupa moves toward the surface of its breeding substrate, often enclosed in an air bubble for emergence as an in aquatic species, or directly from moist substrates in others. Non-biting midge adults live 3-7 days, primarily focused on and oviposition, with males having shorter lifespans of a few days; biting midge females live up to 1-2 months, allowing multiple blood meals and egg batches, while males live shorter periods. Midge voltinism varies from 1 to 10 generations per year based on and , with temperate populations often entering as final-instar larvae to overwinter.

Ecology and Behavior

Habitats and Distribution

Midges, encompassing families such as and , primarily inhabit aquatic and semi-aquatic environments worldwide. in the family , commonly known as non-biting midges, thrive in freshwater systems including lakes, ponds, rivers, streams, bogs, and marshes, where their larvae develop in the underlying sediments and organic-rich substrates. In contrast, , or biting midges, favor coastal and marshy habitats such as swamps, mangroves, shallow ponds, and floodplains, with larvae often occupying moist soils, decaying vegetation, mud, or sand along shorelines. The global distribution of midges is cosmopolitan, spanning nearly all continents and biomes except the most extreme polar interiors, with present across all major landmasses including . Diversity is particularly high in tropical regions, where warm, humid conditions support hyperdiverse communities, as observed in swamp forests of and island ecosystems like , . Polar species, such as the Antarctic midge Belgica antarctica (), exemplify adaptations to cold extremes, inhabiting coastal terrestrial and freshwater niches along the , though rapid winter warming as of 2022 poses survival threats to its larvae. Midges occupy a broad altitudinal range, from to elevations exceeding 5,000 meters. In the , cold-tolerant species like Diamesa () have been documented in glacial habitats at altitudes of 5,100–5,600 meters, where they endure subzero temperatures and low oxygen levels. At the microhabitat scale, midge larvae predominantly reside in benthic sediments of their aquatic breeding sites, burrowing into soft mud or among to feed and develop, while adults remain in close proximity to these areas for mating and oviposition. This distribution ties into their aquatic larval stages, which require stable, nutrient-rich substrates for survival. In the , warming has driven poleward distributional shifts in midge populations, with increased abundances and outbreak frequencies reported in and due to extended warm seasons and altered patterns. For instance, species in have shown prolonged seasonal activity, expanding their range northward and heightening risks of vector-borne transmission. As of 2025, models predict further global range expansions for , amplifying risks. These trends underscore midges' sensitivity to rises, potentially reshaping their ecological roles in higher latitudes.

Feeding and Reproduction

Adult midges in the family , commonly known as non-biting midges, primarily feed on , , honeydew, and other sugar-rich substances to sustain their short adult lives. In contrast, females of the biting midge family require blood meals from vertebrates to obtain proteins necessary for egg development, while both sexes consume ; their specialized mouthparts include serrated mandibles and maxillae that lacerate to facilitate feeding. Larvae of most midge species, particularly , are detritivores that consume decaying , , and microorganisms in aquatic or semi-aquatic environments. However, larvae in certain gall midge species of the family are predatory, actively hunting small arthropods such as , spider mites, and mealybugs. in midges often occurs in lekking swarms formed by males near visual landmarks like hilltops or surfaces, where females select mates based on display behaviors. In some species, acoustic signals produced by wing beats during swarming serve as cues to attract females and deter rivals. Antennae in both sexes aid in detecting pheromones released during these aggregations. Reproduction in midges is predominantly sexual, though occurs rarely in isolated populations of certain . Females typically lay batches of 50 to 300 , depending on and environmental conditions, with egg strings or masses deposited in moist substrates suitable for larval development. Dispersal in adult midges is generally limited, with flight distances rarely exceeding 1 to 2 kilometers under normal conditions, which constrains between populations and promotes local genetic differentiation. Wind-assisted movement can occasionally enable longer-range transport, but self-powered flight remains the primary mode influencing .

Types of Midges

Non-Biting Midges

Non-biting midges, primarily from the family , constitute the most diverse and abundant group of non-hematophagous midges, with over 10,000 described species worldwide. These small flies, often resembling mosquitoes but lacking biting mouthparts, play crucial roles in freshwater ecosystems, where their aquatic larvae dominate benthic communities. Chironomid larvae, commonly known as bloodworms due to their hemoglobin-rich bodies, exhibit varying tolerances to environmental stressors, making them valuable bioindicators of . The larvae of many species demonstrate high tolerance to , particularly organic enrichment from and , allowing them to thrive in degraded habitats where other macroinvertebrates decline. This resilience positions them as key indicators for assessing organic levels in streams and lakes, with community composition shifts signaling deteriorating conditions. For instance, tolerant genera like Chironomus often dominate in polluted waters, providing early warnings for ecosystem health. Ecologically, Chironomidae serve as a primary food source for a wide array of predators, including fish, birds, amphibians, and aquatic invertebrates, thereby supporting higher trophic levels in food webs. Their larvae also function as efficient decomposers, processing and in sediments, which facilitates and maintains . This dual role enhances and stability in freshwater environments, underscoring their overlooked positive contributions. Despite their benefits, mass emergences of adult Chironomidae can create nuisance conditions, particularly in the Great Lakes region, where synchronized swarms—sometimes referred to as "midge storms"—overwhelm shorelines during warmer months. These events, driven by favorable water temperatures around 15–20°C, involve billions of individuals mating and laying eggs, leading to temporary accumulations on beaches and structures. In areas like Lake Erie and Lake Michigan, such emergences peak in spring and fall, affecting recreation but posing no health risks. Specific examples include lake flies of the Chironomus, which are widely used in programs to evaluate and integrity. Chironomus larvae, with their tube-dwelling habits in sediments, respond predictably to contaminants, enabling scientists to quantify through abundance and diversity metrics. These highlight the family's utility in environmental assessments, from urban streams to large lakes. Conservation efforts for face threats from habitat loss due to , dam construction, and drainage, which fragment aquatic environments and reduce larval refugia. However, many species exhibit resilience to , with eutrophication-tolerant taxa proliferating in nutrient-enriched waters, aiding recovery in impacted systems. This adaptability, combined with their role in , supports targeted protection of freshwater habitats to preserve their ecological functions.

Biting Midges

Biting midges belong to the family , a diverse group of small hematophagous flies primarily recognized for their role as vectors of diseases in vertebrates. The family encompasses over 6,000 species across more than 100 genera, but only a few are significant biters of vertebrates. Key hematophagous genera include , which comprises the majority of vector species and affects and humans worldwide, and Leptoconops, known for biting humans and domestic animals in arid and coastal regions. Female biting midges require meals for development and employ specialized mouthparts to feed. The consists of elongated stylets, including serrated mandibles and laciniae from the maxillae, which females use to pierce host and lacerate capillaries, creating a pool. During feeding, they inject containing anticoagulants and vasodilators to prevent clotting and facilitate flow, a process that can last several minutes. These midges transmit several arboviruses of veterinary and medical importance. Culicoides species are primary vectors of bluetongue virus (BTV), an orbivirus causing severe disease in ruminants like sheep and , with outbreaks linked to species such as C. sonorensis and C. imicola. In humans, Culicoides paraensis has emerged as a vector for Oropouche virus (OROV), an orthobunyavirus responsible for fever outbreaks in the ; by the end of 2024, over 16,000 confirmed cases were reported, including expansions to new regions such as (first cases in June 2024) and (first case in November 2024), with two deaths. Outbreaks continued into 2025, with over 12,000 additional cases reported in the by late July, and the first travel-related case in the noted in August 2025. Biting midges exhibit preferences for mammalian and avian hosts, with species-specific variations; for instance, many Culicoides target large mammals like or birds in wetlands. Their activity is predominantly crepuscular, peaking at dawn and dusk when hosts are most accessible, which enhances transmission efficiency. Bites often provoke strong allergic responses due to salivary proteins, resulting in intense localized itching and swelling; in sensitive individuals, including humans and equines, repeated exposure can lead to reactions characterized by chronic .

Human Interactions

Economic and Ecological Impact

Midges play a vital role in aquatic ecosystems as a foundational prey base for various fish species, particularly salmonids. For instance, non-biting midge larvae and adults constitute a significant portion of the diet for subyearling in the Lower Estuary, where comprise the majority of consumed dipterans. Similarly, fry extensively feed on small midges, supporting their growth and overall fishery productivity. Adult midges also contribute to services; non-biting species are among the primary pollinators in environments, facilitating plant reproduction in nutrient-poor soils. Beyond their ecological contributions, midges offer practical benefits in and . Chironomid larvae, rich in proteins and essential fatty acids, serve as a high-quality feed for larval in aquaculture systems, promoting efficient growth and reducing reliance on traditional feeds. Additionally, chironomid communities act as effective bioindicators of and , aiding by signaling levels and degradation in freshwater assessments. However, midges impose substantial economic costs, particularly through tourism disruptions and livestock health impacts. In the Scottish Highlands, swarms of biting midges deter visitors during peak seasons, resulting in estimated annual losses of approximately £286 million to the industry. Biting midges further burden by vectoring diseases like bluetongue virus, which caused outbreaks costing Tunisian livestock farms around €561 million in 2020 alone, including animal losses and treatment expenses. In 2025, biting midges have been implicated in ongoing Oropouche virus outbreaks in , posing emerging risks. exacerbates these issues by expanding the geographic range of biting midges, enhancing their potential as vectors for arboviruses such as bluetongue and potentially increasing outbreak risks in new regions. Culturally, midges feature prominently in as symbols of nuisance or supernatural omens. In traditions, the is depicted in tales as a persistent pest unleashed to torment invaders, reflecting its real-world in rural life. Similarly, Māori narratives incorporate midges among in stories of environmental balance and conflict, portraying them as elements of nature's trials.

Pest Management

Pest management for midges, particularly biting species in the family and non-biting , emphasizes (IPM) approaches that combine multiple strategies to reduce populations while minimizing environmental impact. These methods target both larval and adult stages, focusing on breeding sites in aquatic habitats such as wetlands and standing water. Recent advances prioritize biological and habitat-based controls over broad-spectrum chemicals due to growing concerns over resistance and non-target effects. Biological controls leverage natural predators and microbial agents to suppress midge populations. and larvae are effective predators of midge larvae in aquatic environments, consuming large numbers and helping regulate densities in ponds and wetlands. Similarly, var. israelensis (Bti) is a widely used bacterial that produces toxins lethal to midge and larvae upon ingestion, while sparing beneficial insects, fish, and humans. Bti is applied as pellets or granules to breeding sites and has been effective in significantly reducing larval abundances in treated waters without disrupting wetland ecosystems. Chemical methods, including pyrethroid insecticides like and , are applied via ultra-low-volume (ULV) sprays to control adult midges around or human areas. These synthetic act as neurotoxins, causing rapid knockdown and mortality in exposed adults. Physical barriers provide non-toxic against adult midges entering structures or outdoor spaces. Fine-mesh screens with 20x20 weave or tighter, such as no-see-um netting, effectively block midges while allowing ventilation. UV traps, including plug-in devices and outdoor zappers, attract and capture adults using wavelengths around 350-365 nm, reducing local populations by trapping thousands per unit over extended periods. These traps are particularly useful in IPM as they avoid chemical residues and can be combined with fans for enhanced suction. Habitat modification targets larval development by altering breeding conditions. Wetland drainage or winter drawdowns expose and desiccate overwintering larvae, significantly lowering emergence rates in subsequent seasons. Vegetation management, such as removing decaying organic matter and controlling nutrient runoff from fertilizers, reduces food sources for Chironomidae larvae in eutrophic waters. These practices, when implemented in managed wetlands, can significantly decrease midge densities without harming biodiversity. Emerging technologies offer promising long-term solutions for control. Genetic methods, including drives, have been proposed to suppress populations by biasing of sterility or pathogen-refractory traits. These innovations integrate with traditional IPM to address resistance and habitat constraints effectively.

References

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