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Megachile
Megachile
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Megachile
Megachile lagopoda
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Megachilidae
Genus: Megachile
Latreille, 1802
Subgenera

Over 50 subgenera and 1520 spp., see list

Synonyms
  • Anthophora Fabricius, 1804 (Preocc.)
  • Eumegachile Friese, 1898
  • Anthemois Robertson, 1903
  • Cyphopyga Robertson, 1903
  • Megalochila Schulz, 1906
  • Grosapis Mitchell, 1980
Male Megachile

The genus Megachile is a cosmopolitan group of solitary bees, often called leafcutter bees or leafcutting bees; it also includes the resin bees and mortar bees. While other genera within the family Megachilidae may chew leaves or petals into fragments to build their nests, certain species within Megachile neatly cut pieces of leaves or petals, hence their common name. This is one of the largest genera of bees, with more than 1500 species[1] in over 50 subgenera.[2] The alfalfa leafcutter bee (Megachile rotundata) is managed on a commercial scale for crop pollination, and has been introduced by humans to various regions around the world.

Female leafcutter bee nectaring on Great Valley gumplant. The three scenes repeated at one tenth speed.

Ecology

[edit]

Nests are sometimes constructed within hollow twigs or other similarly constricted natural cavities, but often are in burrows in the ground. Nests are typically composed of single long columns of cells, the cells being sequentially constructed from the deepest portion of the tunnel outwards. The female places an egg in each cell with a supply of food, generally pollen, sometimes mixed with nectar. She builds a cap and walls off the cell. The larva hatches from the egg and consumes the food supply. After moulting a few times, it spins a cocoon and pupates, often after several months of hibernation as a prepupa. It emerges from the nest as an adult. Males, which are typically smaller and emerge in advance of females, die shortly after mating, but females survive for another few weeks, during which time they build new nests. Numerous families of wasps and bees parasitize Megachile nests, including Gasteruptiidae, Leucospidae, Sapygidae, and various kleptoparasitic megachilids, such as the closely related genus Coelioxys. M. rotundata and M. campanulae are among of the first insects documented in scientific literature to use synthetic materials for making nests.[3]

Many Megachile species use cut leaves to line the cells of their nests. It is thought that the leaf discs help prevent the desiccation of the larva's food supply.[1] Various species in the genus, especially those in the subgenus Chalicodoma and related groups, do not use cut leaves to line the cells, but instead use fairly dry plant resin, which they carry in their mandibles. The subgenus Chalicodoma includes the world's largest bee, Megachile pluto, as well as one of the largest megachilids in the United States, the recently introduced Asian species, Megachile sculpturalis.

Some Megachile species have no lobe (arolia) between their claws, thus are unable to climb smooth walls or glass.[4]

Diversity

[edit]

The genus Megachile contains 56 subgenera with 1520 recognized species.[1] See also the list of Megachile species.

Notable subgenera:

Notable species:

[edit]
  • Megachile fortis
    Megachile fortis
  • Megachile ericetorum
    Megachile ericetorum
  • Male Megachile Subgenus Xanthosarus with modified front legs
    Male Megachile Subgenus Xanthosarus with modified front legs
  • Shelter built for Megachile
    Shelter built for Megachile
  • Leafcutter bee life cycle
    Leafcutter bee life cycle
  • Comparison between a modern pupa and a fossil pupa from the La Brea Tar Pits
    Comparison between a modern pupa and a fossil pupa from the La Brea Tar Pits
  • Megachile inimica female
    Megachile inimica female
  • Megachile pugnata pugnata female
    Megachile pugnata pugnata female

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Megachile

View on Grokipedia
from Grokipedia
Megachile is a cosmopolitan of solitary bees belonging to the family and subfamily Megachilinae, encompassing over 1,400 species worldwide, commonly referred to as leafcutter bees but also including bees and mason (dauber) bees that utilize materials like or for nesting. These medium- to large-sized bees (7–17 mm) exhibit a stocky build with a robust head and black often adorned with white bands of setae on the ; females possess a dense (pollen-collecting brush) on the ventral side of the metasoma, while males typically have enlarged forelegs with fringes of hairs used in mating. As solitary nesters, Megachile species construct brood cells in pre-existing cavities such as wood, stems, , or rocks, or sometimes excavate their own burrows; females meticulously cut circular pieces from leaves, petals, or use and to line and partition cells, which are then provisioned with a mixture of and before laying an egg in each. The life cycle involves eggs hatching into legless larvae that feed on the provisions, spin cocoons, and overwinter as prepupae, emerging as adults in spring; multiple generations (up to three or more annually in temperate regions) are common, with males emerging first from nests. behaviors vary from polylectic (visiting many plant families) to oligolectic (specializing on few), and females often exhibit distinctive buzzing and abdomen-lifting during ; these bees are vital pollinators for crops like , apples, and , with species such as M. rotundata commercially managed for alfalfa seed production. The genus's diversity spans numerous subgenera (around 56 globally), reflecting adaptations to varied habitats from arid regions to forests across all continents except and extreme polar areas; in alone, 76 species are recorded, while hosts about 140. Ecologically, Megachile bees support by pollinating wildflowers and are subject to by coelioxys cuckoo bees, underscoring their role in maintaining balance amid threats like habitat loss and pesticides.

Taxonomy and Phylogeny

Etymology and History

The genus name Megachile derives from the Ancient Greek words mégas (μέγας), meaning "large" or "great," and kheîlos (χεῖλος), meaning "lip" or "jaw," in reference to the prominent, enlarged mandibles of females used for cutting leaves to construct nests. This etymological emphasis highlights a defining morphological trait that distinguishes the genus within the bee family Megachilidae. The genus Megachile was formally established by Pierre André Latreille in 1802, building on earlier species descriptions by Johan Christian Fabricius, who named several taxa in the late 18th century, such as Megachile argentata in 1793. In the 19th century, British entomologist William Kirby contributed significantly through works like his 1837 Fauna Boreali-Americana, where he described North American species and refined early classifications of leafcutter bees. These foundational efforts laid the groundwork for understanding Megachile as a diverse group of solitary bees. Throughout the 20th century, taxonomic revisions expanded recognition of the genus's scope, incorporating molecular and morphological data to delineate subgenera and resolve synonyms, culminating in the acknowledgment of over 1,500 species by the early . This evolution reflects ongoing systematic inquiries that have clarified Megachile's position within , from initial Linnaean groupings to modern phylogenetic frameworks.

Classification and Subdivisions

Megachile belongs to the family , within the superfamily of the order , and is classified in the Megachilinae and Megachilini. This placement reflects its shared characteristics with other megachiline bees, such as the possession of scopae on the underside of the for transport. The genus is recognized as the largest within , encompassing approximately 1,520–1,570 described distributed worldwide as of 2025 (including 71 newly described species in the Austrochile). These species exhibit diverse nesting and provisioning behaviors, but the genus is unified taxonomically by features like the robust body form and specialized mouthparts adapted for cutting or gathering materials. Internally, Megachile is subdivided into approximately 56 subgenera, based primarily on morphological traits such as mandibular structure, clypeal punctation, and metasomal features. For instance, the nominotypical subgenus Megachile s.str. includes species with strongly toothed mandibles suited for cutting leaves, while subgenera like Chelostomoides feature mandibles adapted for resin collection and lack the acute cutting edges. Dasymegachile, another prominent subgenus, is characterized by dense, long pilosity covering the body and mandibles with fewer teeth, distinguishing it from more glabrous groups. These criteria facilitate identification and reflect adaptations to specific nesting materials. Phylogenetic analyses have highlighted complex relationships within Megachile, with molecular studies using multi-locus nuclear data confirming its relative to closely related genera like Hoplitis and Osmia, while underscoring close ties to other leafcutter and dauber bee lineages in Megachilini. However, debates persist regarding potential , as cleptoparasitic genera such as Coelioxys appear nested within or sister to Megachile in some reconstructions, prompting calls for further revisionary work to stabilize subgeneric boundaries.

Description

Physical Characteristics

Megachile bees, commonly known as leafcutter bees, are medium to large solitary bees typically ranging in body length from 7 to 17 mm, exhibiting a robust, stocky build with a predominantly black that may appear metallic or include pale integumental areas in certain species. Their overall form is adapted for efficient movement in diverse environments, with a broad head that supports powerful musculature. A distinctive morphological feature of the genus is the large, stout mandibles in females, which are broadened at the apices and equipped with 2 to 7 teeth, enabling precise cutting of leaf material; these mandibles are proportionally large relative to the head, often spanning nearly the full head width. The head itself features a convex clypeus and parallel compound eyes that are typically bare, lacking dense pubescence, which aids in visual navigation. The is parallel-sided and robust, with terga bearing distinct apical fasciae of pale hairs; females possess a dense ventral of white or light-colored hairs on the for collection, a trait unique among many genera as it shifts transport from the legs to the . Leg morphology includes simple claws in females, potential spines on the anterior coxae, and structures that facilitate handling nesting materials, though not primarily for storage. Wing venation is characteristic, with forewings displaying two equally sized submarginal cells and a second recurrent positioned prefurcally. Sensory structures include antennae segmented into 10 flagellar segments in females (11 in males), which house odor-perceiving organs essential for foraging cues. influences these traits, with females generally larger and more robust than males, who often exhibit modified forelegs.

Sexual Dimorphism and Variation

Sexual dimorphism in the genus Megachile is pronounced, with females generally larger than males. This size disparity supports the females' roles in nest provisioning, where they possess more robust mandibles with sharpened, tridentate cutting edges adapted for slicing leaves. Females also feature a dense ventral —a of specialized hairs on the —for efficient collection and transport, which is fuller and more developed compared to any rudimentary structures in males. In contrast, males are typically smaller with narrower abdomens and lack a functional , reflecting their non-provisioning lifestyle. Many male Megachile display facial hair tufts on the clypeus and gena, often pale or golden, which may aid in mate recognition during . Additionally, males frequently have modified forelegs, including elongated basitarsi or spines, as seen in species like M. rotundata, potentially for grasping females during mating. Intraspecific variation within Megachile includes size differences among individuals of the same , linked to resource availability during larval development; for instance, in M. rotundata, limited pollen provisions result in smaller adults, affecting overall fitness. Extreme morphological variations occur in certain subgenera, such as Pseudomegachile, where females exhibit elongated mandibles with extended cutting edges specialized for harvesting tougher plant materials, as in M. ericetorum. These adaptations highlight the genus's diversity in response to ecological niches.

Distribution and Habitat

Global Range

The genus Megachile has a cosmopolitan distribution, present on all continents except , where it inhabits a wide array of environments from temperate to tropical zones. This broad range reflects the adaptability of the genus, with approximately 1,500 described worldwide as of , though diversity gradients show peaks in tropical areas, and over 70 additional species were described in 2025. Highest occurs in tropical regions such as within the Oriental realm and the , contrasting with lower diversity in higher latitudes. In native ranges, Megachile is particularly prominent in the Palearctic and Neotropical realms, the latter supporting more than 400 species across 28 subgenera from to . The , encompassing , hosts approximately 140 in the United States and , while records about 76 , many concentrated in the Mediterranean and central regions. These patterns underscore the genus's dominance in both Holarctic and tropical biogeographic provinces. Human-mediated dispersal has expanded Megachile ranges beyond native distributions; for instance, was introduced to from in the 1930s to enhance seed , leading to its establishment and widespread use in agriculture. Biogeographic patterns also feature notable on isolated landmasses, such as , where high levels of bee species endemicity—around 90% for the island's bee —include several Megachile taxa restricted to this hotspot. Such insular highlights evolutionary divergence driven by geographic isolation in the genus's global spread.

Environmental Preferences

Megachile species, commonly known as leafcutter bees, exhibit a strong preference for open, sunny habitats such as meadows, gardens, prairies, shrublands, and forest edges, where abundant flowering plants and soft-leaved trees or shrubs provide both foraging opportunities and nesting materials. These bees thrive in environments with ample reaching the ground, favoring areas with reduced canopy cover that allow for warmer microclimates conducive to their activity. They generally avoid dense s, where shaded understories limit floral diversity and suitable nesting sites. These bees demonstrate tolerance for a wide range of climates, from arid —where resin-using in subgenera like Callomegachile adapt to dry conditions by incorporating resins into nests—to temperate woodlands and coastal dunes. Their distribution spans from arctic regions to southern and elevations up to 5,000 meters, with richness often peaking in areas of high and low . However, prolonged droughts in habitats can pose risks, though many endure temperatures up to 46–47.5°C. Microhabitat requirements emphasize proximity to nesting substrates, including soil banks, hollow plant stems, decaying wood cavities, beetle borrows, or earthen banks, often within short distances of floral resources. Nesting aggregations may form in these sites, particularly in riverbanks or niches between stones, to optimize protection and resource access. Cavity sizes typically range from 4–10 mm in diameter, influencing based on species-specific needs. Several Megachile species have adapted well to urban environments, thriving in parks, residential gardens, and agricultural fields where artificial nest boxes or natural cracks in buildings serve as substrates near ornamental plantings. This flexibility allows them to persist in human-modified landscapes, provided sunny exposures and diverse vegetation are maintained.

Behavior

Nesting Habits

Megachile bees are solitary nesters that typically utilize pre-existing cavities for brood rearing, such as hollow reeds, bored wood tunnels, abandoned burrows, or ground excavations, which they partition into linear series of individual cells. These cavities vary in diameter, with many species preferring 4–7 mm openings, though preferences can shift seasonally or by species, as observed in trap nest studies where 4 mm tubes were most utilized early in the season. Nesting materials differ across subgenera: leafcutter bees (e.g., ) line cells with precisely cut pieces of leaves or petals, transported using specialized mandibles, while resin bees (e.g., ) employ plant s to construct and seal brood cells, often adding a vestibular cell near the entrance for added protection. Mortar bees, in contrast, mix or with masticated leaves to form partitions and caps. The number of cells per nest varies by species, typically ranging from 5 to 10; for example, resin bee species like M. often have 7–8 cells, arranged from the cavity's rear forward, with the innermost cell completed first. The nesting sequence begins with the female selecting and preparing a cavity, then applying a basal lining of material such as or leaves. She provisions the cell by collecting a pollen-nectar , often dominated by a single plant species like in M. cephalotes, deposits a single on the provision mass, and seals the cell with additional material before repeating the process for subsequent cells. Upon completion, the nest entrance is plugged with , dung, or leaf fragments to deter intruders. To defend against kleptoparasites, Megachile females incorporate barriers like layers, which provide properties and impede access by wasps such as Coelioxys species that lay eggs in host nests to exploit the provisions. Coelioxys is widespread, affecting multiple Megachile species including M. brasiliensis and M. stilbonotaspis, though some nests remain unparasitized through such structural defenses.

Foraging and Diet

Most Megachile species exhibit polylectic foraging behavior, collecting pollen and nectar from a diverse array of flowering plants across multiple families, though some are oligolectic and specialize on pollen from a few plant species. While they are generalists capable of utilizing various floral resources, they show particular preferences for pollen from , , and , which provide abundant and nutritious provisions. This dietary flexibility allows them to adapt to varying floral availability in their habitats, ensuring consistent resource gathering for larval development. Foraging in Megachile is strictly diurnal, with s active from early morning through late afternoon, typically ceasing activity at dusk. A single may undertake 10-20 trips per day, each lasting several minutes, to amass sufficient resources. During these excursions, s cut circular or oval leaf pieces using their mandibles from preferred plants such as roses () and (), which are later used in nest construction. is gathered via specialized scopal hairs on the underside of the , where it adheres and is compacted into moist balls by mixing with regurgitated ; this serves dual purposes, providing immediate energy for the adult and contributing to the larval food mass. Foraging activity in Megachile peaks during the summer months, aligning with the blooming periods of their preferred families and favorable environmental conditions. This seasonal pattern is heavily influenced by floral abundance and moderate temperatures, which support sustained flight and resource collection. The gathered and are briefly stored before being transported to nests for provisioning larval cells.

Ecology and Life Cycle

Pollination Role

Megachile bees serve as effective pollinators across diverse ecosystems, leveraging their foraging behavior to transfer pollen between flowers while collecting provisions for their nests. On a genus-wide scale, Megachile species bolster plant biodiversity in grasslands, meadows, and orchards by pollinating a broad array of native flora, thereby supporting ecosystem stability and reproductive success of wild plants. For instance, Megachile rotundata, the alfalfa leafcutting bee, plays a pivotal role in alfalfa seed production, where managed populations have tripled yields in North America by providing the majority of necessary pollination services, far surpassing contributions from honey bees. These bees' activities extend to maintaining genetic diversity in pollinator-dependent plant communities, indirectly aiding herbivore and seed-dispersal networks. Megachile bees visit crops including alfalfa (Medicago sativa), and have been observed on blueberries (Vaccinium spp.) and tomatoes (Solanum lycopersicum), contributing to seed and fruit set in both wild and agricultural settings through general flower visitation. Certain Megachile species interact with non-native plants, potentially facilitating the spread of invasive in altered habitats. The giant resin bee (Megachile sculpturalis), an in and , preferentially forages on exotic like Sophora japonica and Ligustrum spp., aiding their reproduction and establishment while competing with native pollinators for resources. Such interactions can alter local plant-pollinator dynamics, promoting the proliferation of non-indigenous species in urban and disturbed areas. Within food webs, Megachile bees function as prey for various predators, integrating into trophic structures as a source that sustains higher-level consumers. They are consumed by birds such as bee-eaters and warblers, orb-weaving spiders that ambush foraging individuals, and predatory insects including robber flies and parasitic wasps like Coelioxys spp. and Chrysis spp., which target brood cells. This prey role underscores their contribution to predator populations and overall ecological balance.

Reproduction and Development

Megachile exhibit solitary behaviors, with adults typically emerging in late spring or summer to mate at nest sites or on flowers. Males these areas aggressively, often harassing females in attempts to copulate, while females actively resist most advances, exerting control over and subsequent oviposition. This female-controlled process allows selective fertilization of eggs, influencing offspring sex ratios that can vary from male-biased to female-biased depending on environmental and resource factors. Sex determination in Megachile follows the haplodiploid system typical of , where unfertilized eggs develop into haploid males and fertilized eggs into diploid females. Females thus determine the sex of progeny by controlling release during egg-laying, often producing more females in resource-rich conditions to maximize reproductive output. The life cycle of Megachile encompasses four stages: , , , and , with development occurring within sealed brood cells in the nest. Eggs are laid singly on pollen-nectar provisions; they hatch in 2–3 days into legless, grub-like that consume the mass over approximately 20 days, molting through four instars before spinning a silken cocoon. Pupation follows, lasting 10–14 days, after which adults remain dormant until emergence the following season in temperate regions, where most are univoltine. In temperate zones, Megachile overwinter as non-feeding prepupae encased in cocoons, entering triggered by shortening days and cooler temperatures, with emergence synchronized to spring flowering. In tropical or subtropical areas, species may produce 1–2 generations annually, exhibiting multivoltine patterns without prolonged .

Diversity

Species Count and Distribution

The genus Megachile encompasses over 1,500 described worldwide, distributed across more than 50 , with ongoing taxonomic work revealing additional diversity through new descriptions and revisions. Recent taxonomic revisions, including the description of 71 new in the Australian subgenus Austrochile in 2025, continue to increase the known diversity, particularly in the . This cosmopolitan genus exhibits its highest in tropical and subtropical realms, particularly the Oriental and Neotropical regions, where each supports 300–400 , reflecting adaptations to diverse floral resources and habitats. In temperate zones, species counts are lower; the hosts about 140 species, primarily in , while the Palearctic includes roughly 100, with 76 recorded in alone. The features fewer species overall, limited by historical isolation and fewer suitable nesting substrates. is notable in biodiversity hotspots such as the , where species like Megachile karooensis and M. murina are endemic to the region, underscoring the role of localized habitats in driving . Taxonomic revisions since 2000 have accelerated species accumulation, with key works documenting new taxa and range extensions, particularly in the Neotropics and Palearctic, contributing dozens of additions to the global tally. For instance, catalogues and regional synopses have clarified subgeneric boundaries, revealing previously overlooked endemics and invasive introductions that alter local distributions.

Notable Species and Subgenera

The genus Megachile encompasses over 1,500 distributed across approximately 56 worldwide, showcasing diverse nesting materials and behaviors from leafcutting to collection. Among these, the Megachile s.str. (sensu stricto) represents classic leafcutter bees, characterized by females using precisely cut leaf pieces to construct brood cell linings in pre-existing cavities such as hollow stems or wood borings. A prominent example is , the alfalfa leafcutter bee, native to but widely introduced to , , , and for its efficient of crops; this measures 6-10 mm in length and completes a univoltine life cycle synchronized with alfalfa bloom. In contrast, the subgenus Chelostomoides features resin-collecting bees that partition nest cells with resins rather than leaves, often resulting in smaller, more compact nests in narrow cavities. Megachile campanulae, the bellflower resin , exemplifies this group in , where females (8-11 mm long) specialize on Campanula flowers for both pollen and resin sources, constructing nests in borings or pithy stems with cells sealed by a resin plug. The subgenus Callomegachile includes larger adapted to subtropical and temperate zones, notable for their robust size and use of mixed with wood particles or mud in nest construction. Megachile sculpturalis, the giant (15-24 mm), native to , has become invasive in since 1994 and in since 2008, where it outcompetes native cavity-nesters by provisioning cells with from diverse and sealing them with ; unlike typical leafcutters, it excavates or modifies wooden cavities. Another standout in Callomegachile is , recognized as the world's largest at up to 39 mm in body length, endemic to Indonesian islands and known for nesting in mounds using resinous secretions. In the western Palearctic, the subgenus Chalicodoma highlights dauber bees that employ or mortar-like mixtures for exposed nests on rocks or walls, differing from cavity-nesters in other subgenera. Megachile lapidaria, a common European species in this subgenus (12-15 mm), constructs turreted nests and forages on a broad range of flowers, serving as a model for studying subgenus-specific adaptations in nesting architecture. These examples illustrate the genus's taxonomic diversity, with subgenera like Megachile s.str. emphasizing leaf-based provisioning while Chelostomoides and Callomegachile showcase innovations that enhance nest durability against parasites.

Human Interactions

Agricultural and Economic Importance

Megachile rotundata, commonly known as the alfalfa leafcutting bee, has been commercially reared since the 1970s for pollinating (Medicago sativa) and clover (Trifolium spp.) crops in the United States and . Introduced accidentally from in the late , its managed populations expanded rapidly with the development of artificial nesting boards and incubation techniques, enabling large-scale release programs. An estimated 800 million individuals are released annually across to support seed production on over 70,000 hectares of fields (as of 2021). These bees provide significant agricultural benefits, including seed yield increases of 30-50% in compared to by honey bees alone, due to their efficient tripping of alfalfa flowers. Their solitary nature results in low aggression, with stings far less painful and less likely than those from honey bees (Apis mellifera), making them safer for farm workers and easier to manage in high-density releases. Economically, M. rotundata contributed to North America's production of about 46,000 metric tons of alfalfa seed annually as of 2004, representing two-thirds of global output and supporting forage, export, and livestock industries. Challenges in commercial rearing include disease management, particularly chalkbrood caused by the fungus Ascosphaera aggregata, which can infect up to 20% of brood in U.S. populations. Recent studies (as of 2024) indicate that climate-induced shifts in emergence timing may further challenge synchronization with crop blooms. Fungicides like iprodione applied to nests have proven effective in controlling the without harming bee development. Overcollection of wild cocoons for initial stock has historically impacted naturalized populations, though modern programs rely on incubated managed stocks to mitigate this. Emerging applications include greenhouse pollination for crops like tomatoes (Solanum lycopersicum) and hybrid seed production in orchards, where M. rotundata and related Megachile offer alternatives to bumble bees in controlled environments.

Conservation Status

The genus Megachile, encompassing over 1,400 worldwide, lacks a unified conservation assessment, with most remaining unevaluated by major bodies like the due to data deficiencies. In regions where assessments have been conducted, a notable proportion face risks from anthropogenic pressures. For instance, in , the majority of assessed Megachile are classified as Least Concern or , but exceptions include Megachile cypricola, listed as Critically Endangered owing to severe habitat loss and restricted range, and Megachile diabolica, categorized as Near Threatened. Similarly, Megachile genalis is red-listed as endangered in several European due to the destruction of its specialized nesting habitats in hollow plant stems from agricultural intensification and , though it is assessed as on the European . In North America, where 131 native Megachile species occur, conservation concerns are more pronounced, with up to 47% potentially at risk according to NatureServe rankings. This includes three species ranked as critically imperiled (G1), ten as imperiled (G2), 24 as vulnerable (G3), and 25 considered historical (unrecorded for decades). A representative example is Megachile frugalis, which holds a global rank of G4 (apparently secure) but is critically imperiled (S1) in New York State, reflecting localized declines. Other species, such as Megachile fortis, have experienced range contractions in grassland habitats threatened by conversion to agriculture and development. Common threats to Megachile species include habitat degradation from land-use changes like farming, , and , which eliminate nesting sites such as dead wood, banks, and plant cavities. Pesticide exposure poses a significant risk, particularly to managed pollinators like , which show higher sensitivity than honey bees in fields. Climate change exacerbates vulnerabilities through altered , increased droughts affecting floral resources, and warmer winters disrupting . Pathogens and further compound pressures, with limited dispersal abilities hindering recovery in fragmented landscapes. Conservation strategies emphasize preservation and restoration, such as maintaining snags, brush piles, and diverse flowering plants to support nesting and . Reducing applications near nesting areas and monitoring for diseases are critical, alongside broader initiatives that benefit Megachile through protected areas and . Ongoing surveys are recommended to refine status rankings and track trends, particularly for data-deficient species, including potential updates to IUCN assessments given new data on national declines.

References

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