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Paraneoptera

Paraneoptera is a monophyletic superorder of insects within the infraclass Neoptera, encompassing the orders Psocodea (booklice, barklice, and parasitic lice), Thysanoptera (thrips), and Hemiptera (true bugs, aphids, cicadas, and scale insects), with over 120,000 described species representing more than 10% of all known insect diversity.^[1] These insects are characterized by incomplete metamorphosis, in which nymphs closely resemble adults, and by the absence of cerci, reduced wing venation, and haustellate mouthparts modified into piercing-sucking stylets for feeding on liquids or semi-liquids such as plant sap, blood, or fungal spores.^[2]^[3] Phylogenetically, Paraneoptera originated over 365 million years ago in the Devonian or early Carboniferous period, with diversification driven by adaptations like the evolution of specialized mouthparts and mitochondrial genome reorganizations.^[1] Within the group, Psocodea forms a distinct clade, while Thysanoptera is consistently recovered as the sister group to Hemiptera, together comprising the clade Condylognatha, though the exact position of Psocodea relative to these and other insect lineages remains somewhat unstable in molecular analyses.^[1]^[4] Paraneopterans exhibit diverse ecological roles, from plant pests and disease vectors (e.g., aphids transmitting viruses, lice parasitizing vertebrates) to beneficial predators and pollinators, exerting significant economic and agricultural impacts worldwide.^[2]^[3]

Description

Morphological Features

Paraneoptera are characterized by hemimetabolous development, in which nymphs closely resemble adults and undergo incomplete metamorphosis without a pupal stage.^[2] Paraneopterans exhibit haustellate mouthparts adapted for feeding on liquids or semi-liquids, with piercing-sucking stylets forming a haustellum (beak-like structure) in Thysanoptera and Hemiptera, supported by cibarial muscles and an enlarged postclypeus; in Psocodea, mouthparts are modified for scraping, chewing, or sucking.^[2] Adults typically exhibit a variable number of ocelli (often reduced or absent, 0-3), with compound eyes often reduced in size relative to other insect orders. Antennae are variable, featuring 5-10 segments in many Hemiptera species and filiform structures with 6-9 segments in Thysanoptera.^[2] Distinguishing features among the major groups highlight adaptations in wing structure and mouthpart asymmetry. In Hemiptera, the forewings often develop as hemelytra, with the basal portion hardened (corium) and the apical portion membranous, facilitating protection and flight.^[2] Thysanoptera possess narrow, fringed wings with long marginal setae that aid in flight and dispersal, alongside asymmetrical mouthparts where only the left mandible is developed for piercing.^[2] Psocodea frequently show reduced wings or apterous forms, particularly in parasitic lineages, with beak-like mouthparts modified for chewing or sucking on detritus, fungi, or host tissues.^[2] Sensory structures in certain paraneopterans, such as true bugs and parasitic lice, include trichobothria, hair-like mechanoreceptors distributed on the body and appendages that detect substrate vibrations and air currents, enhancing environmental perception.^[5] Compound eyes are commonly reduced, contributing to a reliance on other sensory modalities in dim or cluttered habitats. Members of Paraneoptera are typically small, ranging from 0.5 to 20 mm in body length, with a cuticle often bearing a waxy coating for protection against desiccation, especially prominent in groups like scale insects within Hemiptera.^[2]

Diversity and Distribution

Paraneoptera encompasses over 120,000 described species (as of 2024), representing a significant portion of insect biodiversity. This superorder includes three primary orders: Hemiptera with approximately 100,000 species, Psocodea with around 11,000 species, and Thysanoptera with more than 7,000 species. These figures underscore the dominance of Hemiptera within the group, which accounts for the majority of paraneopteran diversity, while Psocodea and Thysanoptera contribute substantial but smaller shares.^[6]^[7]^[8]^[9]^[10] Members of Paraneoptera exhibit a cosmopolitan distribution, occurring on every continent and in nearly all terrestrial and some aquatic habitats, with the highest species diversity concentrated in tropical regions. Hemiptera are particularly widespread, dominating both freshwater ecosystems—such as rivers and ponds where aquatic bugs thrive—and terrestrial environments ranging from forests to urban areas. Thysanoptera, or thrips, are commonly associated with flowers, foliage, and agricultural crops, showing elevated abundance in warm, humid tropics but extending into temperate zones. Psocodea, including barklice and booklice, favor moist microhabitats like leaf litter, tree bark, and decaying wood, with global presence from rainforests to arid woodlands.^[11]^[12]^[8]^[13] Endemism is notable in certain paraneopteran lineages, particularly within Psocodea, where Australia hosts a high proportion of unique species adapted to its isolated ecosystems, such as those on endemic rodents or in specialized forest habitats. Conversely, some species have achieved near-global ranges through human-mediated dispersal; for instance, the bed bug Cimex lectularius (Hemiptera), originally temperate in distribution, is now cosmopolitan due to international travel and trade. Regarding conservation, paraneopterans generally face few formally endangered species, but habitat loss from deforestation and urbanization poses risks to barklice populations in Psocodea, which rely on undisturbed moist litter and bark environments, leading to likely declines in native habitats.^[14]^[15]^[16]^[17]

Evolutionary History

Phylogenetic Relationships

Paraneoptera constitutes a monophyletic clade within the superorder Neoptera of the class Insecta, positioned as the sister group to Holometabola, the holometabolous insects encompassing orders such as Coleoptera and Lepidoptera.^[1] This placement is supported by extensive phylogenomic analyses utilizing thousands of orthologous genes from transcriptomic data, which recover Paraneoptera with high bootstrap support (often >90%) and posterior probabilities of 1.00 across multiple datasets.^[18] The clade includes the orders Hemiptera (true bugs), Thysanoptera (thrips), and Psocodea (booklice and parasitic lice), with Condylognatha defined as the monophyletic grouping of Thysanoptera and Hemiptera.^[4] Key morphological synapomorphies defining Paraneoptera include the fusion of the postclypeus to the anteclypeus, resulting in an enlarged, elongate clypeus that accommodates musculature for specialized feeding, and the development of elongated mandibular stylets adapted for piercing substrates such as plant tissues or animal hosts.^[19] These head and mouthpart modifications represent an evolutionary shift from ancestral chewing mechanisms toward haustellate (sucking) types, facilitating diverse feeding strategies across the group.^[20] Molecular evidence bolstering Paraneoptera's monophyly derives from early studies using 18S rRNA sequences, which weakly but consistently placed the group as sister to Holometabola, as well as mitogenome analyses of complete mitochondrial genomes from representatives of all paraneopteran orders.^[21]^[4] More robust support emerged from 2020s phylogenomics, including large-scale transcriptomic datasets confirming the clade's radiation over 365 million years ago in the Devonian period, with crown-group diversification within Psocodea initiating by approximately 292–376 million years ago. A 2024 phylogenomic study further affirms this monophyly as sister to Holometabola with strong support.^[1]^[18] These estimates align with fossil-calibrated molecular clocks and highlight Paraneoptera's ancient origins amid early terrestrial arthropod radiations.^[18] Internally, phylogenomic data strongly support the monophyly of each order, with Psocodea positioned as the basal lineage and Condylognatha (Thysanoptera + Hemiptera) as its sister group; within Condylognatha, Thysanoptera branches before Hemiptera in some analyses, though bootstrap values indicate robust sister-group status between Thysanoptera and Hemiptera overall.^[1] Debates on the monophyly of Psocodea, particularly the historical separation of Psocoptera (booklice) and Phthiraptera (parasitic lice) as distinct orders, have been resolved by cladistic and molecular studies demonstrating their unification under Psocodea, with parasitic lice nested within booklice as a derived clade.^[22] This resolution, based on shared morphological traits like trophi structure and reinforced by genomic data, corrects earlier paraphyletic interpretations and affirms Psocodea's integrity within Paraneoptera.^[23]

Fossil Record

The fossil record of Paraneoptera begins in the Late Carboniferous, with the earliest known specimens attributed to the extinct order Permopsocida, representing a stem-group to the clade and exhibiting primitive wing venation patterns such as an angular pterostigma and a Y-vein formed by the distal fusion of the postcuboanal vein with the first anal vein. These fossils, including the species Carbonopsocus mercuryi from the Moscovian stage (~310 million years ago) in Germany, display specialized rostrum-like mouthparts adapted for sucking, bridging the morphological gap between chewing and piercing-sucking feeding mechanisms in hemimetabolous insects. Permopsocida encompasses over 25 species across three families, spanning from the Early Permian to the mid-Cretaceous, with forms characterized by small, glabrous bodies (~2.4 mm long) and strong basal abdominal constrictions, some resembling roach-like morphologies due to their compact, robust builds.^[24] Major diversification milestones within Paraneoptera are evident across geological periods. Hemiptera underwent significant radiation in the Triassic (~250 million years ago), coinciding with the Middle-Late Triassic insect explosion and the emergence of diverse terrestrial ecosystems, as seen in early heteropteran fossils from deposits like the Cow Branch Formation in Virginia.^[25] Thysanoptera experienced a notable radiation in the Cretaceous (~100 million years ago), linked to the angiosperm diversification, with mid-Cretaceous amber inclusions from Spain preserving thrips such as Gymnopollisthrips minor carrying Cycadopites pollen, indicating early pollination roles that transitioned alongside flowering plant dominance.^[26] Psocodea fossils become more prominent in the Paleogene, particularly from Eocene ambers in regions like the Baltic and Oise (France), yielding well-preserved species such as Tapinella eocenica that highlight increased post-Cretaceous diversity in this suborder.^[27] Preservation biases in the Paraneoptera record favor amber deposits, which provide exceptional morphological detail; for instance, Eocene Baltic amber contains numerous thrips inclusions, revealing fine structures like setae and antennal segments otherwise lost in compression fossils.^[28] The record shows gaps, particularly in the Devonian, due to the soft-bodied nature of early paraneopterans, resulting in underrepresentation before the Carboniferous split between Psocodea and Condylognatha (~357 million years ago).^[29] Recent discoveries in the 2020s, including detailed wing analyses of Carboniferous Permopsocida, are filling Mesozoic gaps by clarifying stem-group transitions and evolutionary links within the clade.

Classification

Higher-Level Taxonomy

Paraneoptera is classified as a superorder of insects within the subclass Pterygota and the infraclass Neoptera, encompassing a monophyletic assemblage of hemimetabolous insects characterized by specialized piercing-sucking mouthparts and reduced cerci.^[30]^[31] The name Paraneoptera was proposed by N. P. Kristensen in 1975 as part of a critical review of hexapod ordinal phylogeny, grouping orders based on shared morphological synapomorphies such as the configuration of the forewing base and labial structures.^[32] The superorder currently includes three extant orders—Hemiptera, Thysanoptera, and Psocodea—along with various extinct taxa from Paleozoic to Cenozoic deposits.^[6] Phylogenetic analyses support the internal structure of Paraneoptera as Psocodea sister to the series Condylognatha, which unites Thysanoptera (thrips) and Hemiptera (true bugs) based on molecular and morphological evidence, including mitochondrial genomes and nuclear transcriptomes.^[4]^[33] This arrangement reflects a diversification estimated around 300–400 million years ago, with Hemiptera as the most species-rich clade exceeding 100,000 described species.^[6] A key taxonomic revision in the post-2000s era integrated the former order Phthiraptera (parasitic lice) into Psocodea as a suborder, driven by molecular data from 18S rDNA and phylogenomic datasets that resolved Phthiraptera as nested within free-living psocids, confirming Psocodea monophyly.^[34]^[23] This merger, first robustly supported in analyses from 2004 onward, has been upheld in 2020s consensus phylogenies using expanded mitogenomic and nuclear data, avoiding outdated separations of lice as a distinct order.^[33] Consequently, Psocodea now accounts for approximately 11,000 species, including both barklice and lice.^[23]^[35] Nomenclaturally, Paraneoptera serves as the prevailing name under the International Code of Zoological Nomenclature (ICZN), though it is alternatively termed Acercaria in some classifications, emphasizing the apomorphic absence of cerci across the group.^[36]^[2] For extinct taxa within Paraneoptera, such as permopsocids and archipsyllids, generic and specific names adhere to ICZN rules, ensuring stability in fossil nomenclature despite challenges from fragmentary preservation.^[36]^[37]

Hemiptera

Hemiptera, one of the largest orders within Paraneoptera, encompasses approximately 100,000 described species, representing a significant portion of insect diversity. This order is traditionally divided into three primary suborders: Heteroptera (true bugs), Auchenorrhyncha (including cicadas, leafhoppers, and planthoppers), and Sternorrhyncha (including aphids, scale insects, and whiteflies), with a fourth minor suborder, Coleorrhyncha, comprising woolly bugs found mainly in southern continents.^[33]^[38] These suborders reflect adaptations to diverse feeding strategies, primarily piercing plant tissues or animal hosts to extract fluids, contributing to Hemiptera's ecological and economic roles.^[39] Diagnostic features of Hemiptera include a specialized rostrum formed by elongated mandibles and maxillae for piercing and sucking liquids such as plant sap or blood, a trait shared with other Paraneoptera through modified mouthparts suited for fluid ingestion.^[40] In the suborder Heteroptera, forewings are modified into hemelytra, with a leathery basal portion and a membranous distal area, while tarsi typically consist of two or three segments ending in paired claws; antennae are usually four- or five-segmented.^[41] Auchenorrhyncha and Sternorrhyncha exhibit more uniform wings, often fully membranous, and lack the hemelytra structure, but all suborders share the rostrum as a key synapomorphy.^[42] Key families illustrate Hemiptera's internal diversity. In Auchenorrhyncha, the Cicadidae family includes cicadas, known for their loud calls produced by tymbal organs in males, with over 3,000 species worldwide. Sternorrhyncha features the Aphididae, the largest aphid family with more than 4,000 species, many of which are polyphagous plant feeders capable of rapid reproduction through parthenogenesis. In Heteroptera, the Reduviidae encompass assassin bugs, predatory species numbering around 7,000, which use sticky hairs or camouflage to capture prey. Several Hemiptera groups hold economic significance as pests; for instance, the phylloxera Daktulosphaira vitifoliae (Phylloxeridae, Sternorrhyncha) devastated European vineyards in the 19th century by feeding on grape roots, prompting widespread grafting onto resistant rootstocks.^[43]^[44] Hemiptera represent a basal lineage within Paraneoptera, with their divergence from other paraneopteran orders estimated at around 354 million years ago based on molecular and fossil evidence. The group's fossil record extends to the Permian period, with early representatives like the Archescytinidae from Lower Permian deposits showing primitive hemipteran traits such as short rostra and simple wing venation, indicating an ancient origin predating the diversification of modern suborders.^[45]^[46] This deep-time persistence underscores Hemiptera's evolutionary success, with over 145 extinct families documented, reflecting waves of diversification and extinction across geological eras.^[11]

Thysanoptera

Thysanoptera, commonly known as thrips, is an order of small insects comprising over 6,400 described species worldwide, divided into two suborders: Terebrantia, with a saw-like ovipositor in females, and Tubulifera, characterized by a tubular tenth abdominal segment.^[47]^[48] The name Thysanoptera derives from the Greek words thysanos (fringe) and pteron (wing), reflecting the distinctive fringed margins of their narrow wings, which are present in most adults but absent in some brachypterous or apterous forms.^[49] As members of the Condylognatha clade, thrips exhibit incomplete metamorphosis and are distinguished from related orders by their minute size, typically 0.5–5 mm in length, and specialized adaptations for plant-associated lifestyles.^[50] Key diagnostic traits of Thysanoptera include an asymmetrical mouth cone formed by the labrum, labium, and maxillae, with the right mandible vestigial or entirely absent, allowing only the left mandible to function in rasping plant tissues.^[48]^[51] This mouthpart configuration enables a rasping-sucking feeding mechanism, where thrips puncture epidermal cells to extract fluids, pollen, or fungal spores, often leaving silvery scars on plant surfaces. The abdomen is invariably 10-segmented, lacking cerci, and features 6–10-segmented antennae that are short and filiform.^[52]^[48] The order encompasses nine families, with Thripidae (suborder Terebrantia) as the largest and most economically significant, including over 2,800 species of common thrips, many of which are pests such as the Western flower thrips (Frankliniella occidentalis), a global vector of tospoviruses affecting crops like tomatoes and ornamentals.^[53]^[54] Phlaeothripidae (suborder Tubulifera) represents the other dominant family, with around 3,500 species featuring a tube-like postabdominal structure in females for oviposition, and encompassing a wide range of habits from predatory to gall-inducing forms.^[55]^[56] Unique aspects of thysanopteran biology include social behaviors in certain species, particularly within Phlaeothripidae, where gall-forming thrips like those in the genus Kladothrips exhibit eusociality with sterile soldier castes that defend colonies using enlarged forelegs and modified mouthparts.^[57]^[58] Many thrips species act as vectors for plant viruses in agriculture, transmitting over 20 tospoviruses through persistent propagative transmission during feeding, leading to significant crop losses in vegetables, fruits, and ornamentals.^[54] The fossil record of Thysanoptera extends to the Late Triassic, approximately 220 million years ago, with early representatives like Triassothrips indicating an ancient origin tied to gymnosperm pollination.^[47]^[59]

Psocodea

Psocodea is an order of insects within the superorder Paraneoptera, encompassing both free-living forms traditionally classified as Psocoptera (such as barklice and booklice) and obligate parasitic forms known as Phthiraptera (true lice). This group comprises approximately 11,000 described species, distributed across diverse habitats from forest litter and bark to the feathers and fur of vertebrate hosts.^[60] The order is characterized by a single origin of parasitism, with Phthiraptera evolving from within the free-living psocopterans, rendering the traditional Psocoptera paraphyletic.^[23] The suborders of Psocodea include Psocomorpha (the largest, with over 3,600 species of barklice in 25 families), Troctomorpha (around 500 species of booklice and related forms in 9 families), Trogiomorpha (about 400 species in 5 families), and Phthiraptera (roughly 5,000 species of lice in 16 families).^[61] Psocomorpha and the other free-living suborders are primarily detritivores or fungivores inhabiting moist, organic substrates, while Phthiraptera are ectoparasites specialized for life on birds and mammals. Monophyly of Psocodea has been robustly confirmed by phylogenomic analyses using thousands of orthologous genes, resolving earlier uncertainties from smaller datasets and establishing its position as sister to Condylognatha (Thysanoptera + Hemiptera) within Paraneoptera.^[1]^[23] Diagnostic morphological traits of Psocodea include a swollen postclypeus, reduced number of tarsomeres (typically 2 or 3), and modified chewing mouthparts adapted for grinding or piercing organic material.^[61] Many species exhibit reduced or absent compound eyes and ocelli, short filiform antennae, and a tendency toward wing reduction or complete aptery, particularly in parasitic forms and some free-living booklice.^[8] Free-living members resemble delicate, soft-bodied barklice with nymphoid adults in apterous morphs, whereas Phthiraptera are dorsoventrally flattened, apterous ectoparasites with beak-like mouthparts for feeding on blood, skin, or feathers.^[62] Major groups within Psocodea highlight its ecological duality. In free-living lineages, the family Psocidae represents common barklice (e.g., genera like Psocus), which scavenge fungi and algae on tree bark, while Liposcelididae includes cosmopolitan booklice (e.g., Liposcelis) that infest stored products and homes.^[61] Among parasitic lice, the family Pediculidae encompasses human-specific species like the head louse (Pediculus humanus), and Philopteridae comprises over 3,000 species of bird lice exhibiting extreme host specificity, with many genera restricted to single bird families or even species.^[23] This host fidelity in Phthiraptera, often cospeciating with avian or mammalian hosts, underscores adaptations like camouflage on feathers and specialized claws for gripping.^[63] The taxonomic unification of Psocoptera and Phthiraptera into Psocodea addresses historical splits based on lifestyle, with molecular phylogenetics from the 2010s providing definitive evidence through multi-gene and transcriptomic data. Studies such as those analyzing 18S rDNA and mitogenomes initially suggested nesting of lice within psocopterans, but comprehensive phylogenomics in 2018 and 2021 solidified the monophyletic framework, influencing modern classifications like those in Lienhard and Smithers' catalogs.^[1]^[23] This integration emphasizes shared apomorphies, such as hypopharyngeal sclerites in mouthparts, over ecological divergence.^[62]

Extinct Taxa

The extinct order Permopsocida represents the most prominent fossil-only group within Paraneoptera, encompassing over 20 genera across three families (Archipsyllidae, Permopsocidae, and Psocidiidae) and spanning from the Permian to the mid-Cretaceous (approximately 299–100 million years ago).^[24] These insects are characterized by a flattened head with divided genae, four-segmented tarsi, and wing venation featuring a pterostigma and two anal veins, including an elongated pronotum in some species and reduced venation patterns that suggest transitional forms between primitive chewing mouthparts and the piercing-sucking structures of modern paraneopterans.^[24] Taxonomically, Permopsocida is positioned as a stem group to Condylognatha (Thysanoptera + Hemiptera) within Paraneoptera, outside the crown groups of extant orders, with key genera such as Permopsocus (from Permian deposits) and Psocorrhyncha (from Triassic amber) exemplifying this placement.^[24] Their significance lies in providing the earliest evidence of suction-feeding adaptations in hemimetabolous insects, documenting a 185-million-year evolutionary bridge toward the diverse mouthpart morphologies seen in living Paraneoptera.^[24] Other extinct lineages include the orders Miomoptera and Hypoperlida, both redefined as stem-group Paraneoptera (specifically stem Acercaria) based on shared wing venation features like a common stem of R + M + CuA and pterostigmal structures.^[64] Miomoptera, known from the Late Carboniferous to Middle Permian (about 300–260 million years ago), includes genera such as Mazonopsocus with long, possibly two-segmented cerci and small body sizes, contributing to calibrating the early diversification of the clade.^[64] Hypoperlida, restricted to the Permian (approximately 299–252 million years ago), features short, one-segmented cerci and is represented by limited genera like those in Hypoperlidae, highlighting early neopteran transitions within the group.^[64] These taxa are not nested within modern orders, underscoring their role as basal paraneopterans. Recent amber discoveries from the Late Triassic of Queensland (e.g., Dinmopsylla semota in Archipsyllidae) and Cretaceous Burmese deposits (e.g., Bittacopsocus with bizarre elongated mouthparts) have expanded the known diversity of Permopsocida, adding Triassic species and reinforcing their evolutionary persistence until the mid-Cretaceous extinction.^[65]^[66]

Biological Significance

Ecological Roles

Paraneoptera occupy diverse trophic levels within ecosystems, serving as herbivores, predators, and detritivores that influence energy flow and nutrient dynamics. In Hemiptera, herbivorous groups such as aphids (Sternorrhyncha) feed on plant sap, acting as primary consumers that can alter plant physiology and community structure by inducing defensive responses or facilitating nutrient transfer through excretion. Predatory Hemiptera, exemplified by assassin bugs (Reduviidae), regulate populations of other arthropods by ambushing and injecting enzymatic saliva into prey, thereby contributing to biological control in terrestrial and aquatic food webs. Psocodea, particularly barklice, function as detritivores by consuming fungi, algae, and decaying organic matter in leaf litter and under bark, accelerating decomposition and nutrient recycling in forest ecosystems. Certain paraneopterans engage in symbiotic relationships that enhance ecosystem stability. Thysanoptera, or thrips, serve as minor pollinators in specialized floral systems like thripophily, transferring pollen via body adhesion while feeding on floral tissues, which supports reproduction in plants such as those in the Ericaceae family. Within Hemiptera, aphids form mutualistic associations with ants, where ants protect aphids from predators in exchange for honeydew, a sugar-rich exudate that influences ant foraging behavior and indirectly boosts aphid population dynamics in herbivore communities. Paraneoptera play keystone roles in biodiversity and food web interactions, often as prey that sustains higher trophic levels. Cicadas (Hemiptera: Cicadidae), during mass emergences, provide a pulsed resource boom for birds and other predators, temporarily rewiring forest food webs by reducing predation on alternative prey like caterpillars and enhancing avian reproductive success. Barklice in Psocodea further support biodiversity by hastening the breakdown of woody debris, promoting fungal growth and soil fertility that benefits decomposer communities. Recent studies highlight the role of thrips microbiomes in facilitating plant pathogen transmission; gut bacteria in species like onion thrips (Thrips tabaci) aid in viral acquisition and vectoring by modulating host immunity and pathogen persistence, underscoring paraneopterans' influence on disease dynamics in plant ecosystems.

Interactions with Humans

Paraneoptera species have significant negative impacts on human agriculture, primarily through Hemiptera and Thysanoptera acting as pests that cause substantial economic losses. Aphids and scale insects within Hemiptera, such as Aphis glycines and various Coccoidea, feed on plant sap, leading to reduced crop yields, transmission of plant viruses, and annual global damages estimated in the billions of dollars; for instance, soybean aphids alone inflict losses ranging from $1 billion to $4.7 billion yearly in the United States (estimates from the 2010s) due to direct feeding and sooty mold contamination.^[67] Thysanoptera, particularly species like Frankliniella occidentalis, damage a wide array of crops including fruits, vegetables, and ornamentals through rasping feeding and as vectors for tospoviruses, resulting in severe yield reductions; tomato spotted wilt virus, transmitted by these thrips, causes economic losses exceeding $1 billion annually worldwide.^[68] In medical and veterinary contexts, certain Paraneoptera pose direct health risks as disease vectors or biting pests. Phthiraptera, including body lice (Pediculus humanus corporis), transmit epidemic typhus caused by Rickettsia prowazekii, as well as trench fever (Bartonella quintana) and relapsing fever (Borrelia recurrentis), with historical outbreaks linked to overcrowding and poor sanitation leading to high mortality rates.^[69] Bed bugs (Cimex lectularius, Hemiptera) have resurged globally since the early 2000s, partly due to widespread insecticide resistance, particularly to pyrethroids like deltamethrin, complicating control efforts and causing increased infestations in urban environments with associated allergic reactions and psychological distress.^[70]^[71] Some Paraneoptera offer beneficial applications in human industries. Scale insects such as Dactylopius coccus (Hemiptera) are cultivated for cochineal dye, a carminic acid-based pigment extracted from their bodies, historically vital for textiles, cosmetics, and food coloring in Mesoamerican and European cultures, and still used today for its vibrant reds and stability.^[72] Certain Psocodea, like predatory forms of Liposcelis species, contribute to biocontrol by preying on eggs and small stages of stored-product pests, though their use remains limited compared to other agents.^[73] Culturally, Paraneoptera feature prominently in human folklore and traditions, often symbolizing transformation and renewal. Cicadas (Hemiptera: Cicadidae), with their periodical emergences every 13 or 17 years, hold symbolic importance in various societies; in ancient Chinese and Greek lore, they represent immortality and resurrection due to their life cycle of prolonged nymph stages followed by dramatic adult appearances, influencing art, literature, and rituals.^[74] Management of Paraneoptera pests emphasizes integrated pest management (IPM) strategies to minimize chemical use and economic impacts. IPM for aphids, thrips, and scale insects integrates monitoring, cultural practices like crop rotation, biological controls such as introducing natural enemies, and targeted insecticides, reducing reliance on broad-spectrum treatments and sustaining agricultural productivity. As of 2025, ongoing challenges include insecticide resistance in key vectors like thrips.^[75] For lice and bed bugs, IPM incorporates sanitation, heat treatments, and resistance-monitoring to address vector-borne diseases and infestations effectively.^[76]

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