Cavity-nester
Guides
Ancistrocerus
mason wasps, potter wasps
Ancistrocerus is a genus of solitary mason wasps in the subfamily Eumeninae. Females construct nests using mud, either in pre-existing cavities or as free-form mud cells attached to hard surfaces. They provision nests with paralyzed caterpillars as food for their larvae. Males are distinguished by hooked antennae tips. The genus has a nearly worldwide distribution, with notable species in North America, Europe, and Asia.
Ancistrocerus albolacteus
Ancistrocerus albolacteus is a solitary mason wasp in the family Vespidae. Like other members of the genus Ancistrocerus, it nests in pre-existing cavities and provisions its young with paralyzed caterpillars. The species is part of a diverse group of potter and mason wasps that play important roles in controlling moth populations.
Ancistrocerus albophaleratus
White-banded Potter Wasp
Ancistrocerus albophaleratus is a solitary mason wasp in the subfamily Eumeninae, commonly known as the White-banded Potter Wasp. Like other Ancistrocerus species, it is a cavity-nesting wasp that constructs nests using mud in pre-existing hollows. The species is part of a genus characterized by distinctive morphological traits including a transverse carina on the first abdominal segment. It is native to North America with confirmed records in the northeastern United States.
Ancistrocerus campestris
Walden's Mason Wasp
Ancistrocerus campestris is a solitary mason wasp in the subfamily Eumeninae. Adults reach approximately 10 mm in length. Females construct nests in pre-existing cavities such as beetle borings in wood, hollow twigs, or abandoned mud dauber nests, partitioning them with mud into individual cells. The species is distinguished by distinctive yellow markings on the abdomen and a characteristic pattern on the rear of the thorax. It preys specifically on caterpillars of the moth families Amphisbatidae and Gelechiidae.
Ancistrocerus parietum
Wall Mason Wasp
Ancistrocerus parietum is a solitary mason wasp native to Europe that was introduced to North America, first recorded from Ithaca, New York in 1916. It has since gradually extended its range across the northeastern United States and into Canada. The species is associated with dead deciduous wood for nesting and has shown population decline in parts of its native range, possibly due to habitat loss. Populations in southern Finland may produce two generations per year.
Ancistrocerus spilogaster
Ancistrocerus spilogaster is a solitary mason wasp in the subfamily Eumeninae, described by Cameron in 1905. As with other members of the genus Ancistrocerus, it exhibits the diagnostic transverse carina on the first abdominal tergum. The species is part of a diverse genus of potter and mason wasps that construct nests using mud and provision cells with paralyzed caterpillars for their developing larvae. Specific biological details for A. spilogaster remain poorly documented in published sources.
Ancistrocerus tuberculocephalus
Ancistrocerus tuberculocephalus is a solitary mason wasp in the subfamily Eumeninae. The species is divided into two subspecies with distinct geographic ranges in western North America. Females nest in pre-existing cavities including abandoned mud dauber nests, hollowed sumac twigs, and old beetle borings in dead wood. They provision each cell with paralyzed caterpillars as food for their developing larvae. The species has been observed feeding on aphid honeydew.
Anthidium
Wool Carder Bees, Carder Bees, Potter Bees
Anthidium is a genus of solitary bees in the family Megachilidae containing approximately 80 species. These bees are commonly known as wool carder or potter bees due to their distinctive nest-building behavior: females collect plant hairs, conifer resin, mud, or combinations thereof to construct brood cells. Unlike leafcutter bees in the same family, Anthidium species do not cut leaf pieces. They possess pollen-carrying scopa exclusively on the ventral surface of the abdomen, a characteristic trait of Megachilidae. The genus is primarily distributed in the Northern Hemisphere and South America.
Anthidium florentinum
Florentine Woolcarder Bee, European wool carder bee
Anthidium florentinum is a medium to large solitary bee in the family Megachilidae, commonly known as the Florentine wool carder bee. Native to the Mediterranean region, it has been introduced to multiple continents including North America, South America, Africa, and Asia. Males are highly territorial and defend floral resources against conspecifics and other bees. Females collect plant trichomes (wool) to line nest cells constructed in pre-existing cavities. The species has been detected in the Canary Islands through citizen science, representing a recent range expansion to oceanic archipelagos.
Anthidium manicatum
European wool carder bee, wool carder bee
Anthidium manicatum, the European wool carder bee, is a solitary, cavity-nesting bee in the family Megachilidae. Females collect plant trichomes (hairs) from leaves such as lamb's ears (Stachys byzantina) to line nest cells, giving the species its common name. Males are highly territorial, defending patches of flowering plants against conspecific males and other pollinators. The species exhibits unusual sexual dimorphism: males are larger than females, contrary to most solitary bees. Native to Europe, Asia, and North Africa, it has become a widespread invasive species across North America, South America, New Zealand, and the Canary Islands after accidental introduction.
Anthidium oblongatum
oblong woolcarder bee
Anthidium oblongatum is a solitary bee in the family Megachilidae, commonly known as the oblong woolcarder bee. Native to Eurasia and North Africa, it has been introduced to North America and South America, with a first record in central Chile documented in 2025. Females construct nests using plant fibers collected from leaves, earning the 'woolcarder' common name. The species shows strong floral specialization, primarily foraging on Fabaceae, Crassulaceae, and Resedaceae.
Atoposmia
Atoposmia is a genus of bees in the family Megachilidae, tribe Osmiini. The genus was established by Cockerell in 1935 and is part of the diverse megachilid bee fauna. These bees are solitary and nest in pre-existing cavities, with females constructing brood cells using collected materials.
Auplopus architectus architectus
Auplopus architectus architectus is a small spider-hunting wasp in the family Pompilidae. Females construct distinctive barrel-shaped mud cells to house their offspring, provisioning each cell with paralyzed spiders as food. The species is part of a genus known for unique nest-building behavior among pompilid wasps, which typically dig burrows rather than construct free-standing mud structures.
Auplopus mollis
Auplopus mollis is a small spider wasp in the family Pompilidae, tribe Auplopini. Females construct distinctive free-standing mud cells, typically barrel-shaped and approximately 15 mm long by 7–10 mm wide, often stacked end-to-end in rows of two to five. The species hunts non-web-building spiders, amputates their legs to facilitate transport, and provisions each mud cell with multiple paralyzed spiders before laying a single egg. Adults feed on aphid honeydew rather than visiting flowers.
Ceratina acantha
small carpenter bee
Ceratina acantha is a species of small carpenter bee in the family Apidae, native to Central and North America. It is one of numerous Ceratina species that contribute to wild bee pollination services, though like most small carpenter bees, it is not among the dominant crop-pollinating species. These bees are solitary or weakly social and nest in pre-existing cavities in dead plant material. The species has been documented in studies examining pollinator responses to flower density, showing flexible foraging patterns compared to larger social bees.
Chelostoma
Scissor Bees
Chelostoma is a genus of solitary bees in the tribe Osmiini (family Megachilidae), comprising approximately 56-60 described species across five subgenera. These bees are predominantly Palaearctic in distribution and are notable for their high degree of pollen specialization: most species are strict oligoleges, collecting pollen from flowers of a single plant genus, subfamily, or family. Common host plant associations include Campanula (bellflowers), Ornithogalum, Ranunculus, Asteraceae, and Brassicaceae. Nesting occurs in preexisting cavities in dead wood or hollow plant stems, with females constructing brood cell partitions and nest plugs using mud often reinforced with pebbles and sand grains.
Chelostoma phaceliae
Chelostoma phaceliae is a solitary bee species in the family Megachilidae, described by Michener in 1938. Like other members of the genus Chelostoma, it is a specialist bee with narrow ecological associations. The species is native to North America and is part of the diverse assemblage of solitary bees that provide essential pollination services without forming social colonies.
Chelostoma rapunculi
Rampion Scissor Bee
Chelostoma rapunculi is a solitary bee in the subgenus Gyrodromella (family Megachilidae), commonly known as the Rampion Scissor Bee. It is an oligolectic species specialized on Campanula host plants, though females occasionally visit non-host plants including Geranium sanguineum and Malva moschata. Nesting occurs in preexisting linear cavities in dead wood or hollow stems, with cells partitioned using mud and pebbles. The species is native to the Palaearctic region and has been introduced to North America.
Dianthidium
Pebble bees, resin bees
Dianthidium is a genus of solitary bees in the family Megachilidae, commonly known as pebble bees or resin bees. The genus comprises at least 20 described species in North America. These bees are distinguished by their use of plant resins in nest construction, gathering resins from various plant sources to build and seal their nest cells. They are cavity-nesting bees that utilize pre-existing hollows such as beetle borings in dead wood or hollow twigs. Dianthidium species are important pollinators and serve as hosts for parasitic wasps in the family Leucospidae.
Dianthidium arizonicum
Arizona Pebble Bee
Dianthidium arizonicum is a species of resin bee in the family Megachilidae, first described by Rohwer in 1916. It is native to the southwestern United States, particularly Arizona. Like other members of the genus Dianthidium, it is a solitary bee that constructs nests using plant resins. The species has been documented nesting in artificial bee blocks, indicating adaptability to human-provided nesting structures.
Dianthidium curvatum curvatum
A subspecies of resin bee in the family Megachilidae, Dianthidium curvatum curvatum belongs to a genus of solitary bees known for constructing nests using plant resins. The species epithet "curvatum" refers to a curved structural feature, likely of the mandible or other mouthpart. As with other Dianthidium species, this bee is a cavity nester that provisions its cells with pollen and nectar.
Dianthidium floridiense
Florida Pebble Bee
Dianthidium floridiense is a species of resin bee in the family Megachilidae, commonly known as the Florida Pebble Bee. It is native to North America and belongs to a genus of solitary bees that construct nests using plant resins. Like other Dianthidium species, females likely nest in pre-existing cavities such as hollow twigs or beetle borings in dead wood, partitioning cells with resin walls and sealing the entrance with a resin plug. The species is part of a group known as "pebble bees" or "resin bees" due to their distinctive nest construction behavior.
Dianthidium pudicum
Modest Pebble Bee
Dianthidium pudicum, commonly known as the Modest Pebble Bee, is a species of resin bee in the family Megachilidae. It is native to North America and belongs to a genus characterized by nesting in pre-existing cavities and using resin to construct and seal nest cells. Like other Dianthidium species, it is a solitary bee that provisions its nests with pollen and nectar for its offspring. The species has been documented in bee block monitoring studies, indicating its use of artificial nesting structures in urban and suburban environments.
Dianthidium pudicum pudicum
Dianthidium pudicum pudicum is a subspecies of resin bee in the family Megachilidae. Like other members of the genus Dianthidium, it constructs nests using plant resins, creating distinctive resin plugs and partitions within pre-existing cavities such as hollow twigs or beetle borings. The subspecies was described by Cresson in 1879 and occurs in North America.
Dianthidium texanum
Texas Pebble Bee
Dianthidium texanum is a species of resin bee in the family Megachilidae, commonly known as the Texas Pebble Bee. Native to North and Middle America, this solitary bee constructs nests in pre-existing cavities such as hollow twigs or beetle borings, using resin to partition cells and seal the nest entrance. The species has been documented in bee block monitoring studies and is known to be parasitized by leucospid wasps. Adults are active during summer months and visit flowers for nectar and pollen.
Dipogon calipterus
spider wasp
Dipogon calipterus is a small spider wasp in the family Pompilidae. Females hunt spiders on tree trunks, sting them into paralysis, and provision underground nests with them. The species exhibits ant-mimicry through dark wing bands and is rarely observed due to its cryptic appearance and behavior. Three subspecies are recognized with scattered distributions across eastern and southern North America.
Dipogon graenicheri atratus
A subspecies of spider wasp in the family Pompilidae, characterized by its dark coloration. Like other Dipogon species, it is a forest-dwelling wasp that hunts spiders on tree trunks. The subspecies was described by Townes in 1957 and belongs to a genus known for ant-mimicking appearance due to dark wing bands.
Dipogon graenicheri graenicheri
Dipogon graenicheri graenicheri is a subspecies of spider wasp in the family Pompilidae, described by Banks in 1939. As with other members of the genus Dipogon, it is a predator of spiders, hunting on tree trunks in forested habitats. The subspecies is part of a group characterized by dark-banded wings that provide ant-mimicry camouflage.
Euodynerus hidalgo
Hidalgo Mason Wasp
Euodynerus hidalgo is a widespread mason wasp (subfamily Eumeninae) found across North America from the Atlantic to Pacific coasts. The species is divided into three subspecies with variable coloration, ranging from predominantly black with yellow markings to forms with reduced red markings. Females nest in pre-existing cavities including abandoned mud dauber nests, solitary bee burrows, and even mortar crevices in buildings. Like other mason wasps, they provision nests with paralyzed caterpillars as food for their larvae.
Euodynerus hidalgo boreoorientalis
A subspecies of mason wasp in the subfamily Eumeninae, distributed along the Eastern Seaboard of North America. Females nest in pre-existing cavities such as old bee or beetle borings in twigs and stalks, provisioning cells with paralyzed caterpillars. This subspecies is distinguished from the nominate form by reduced red coloration, appearing mostly black with sparse yellow markings.
Euodynerus hidalgo hidalgo
Euodynerus hidalgo hidalgo is a subspecies of mason wasp in the subfamily Eumeninae. It is one of three subspecies of E. hidalgo, distinguished by its coloration and distribution in the southern United States and Mexico. The wasp nests in pre-existing cavities such as mortar crevices, abandoned mud dauber nests, and old solitary bee burrows. Females provision nests with paralyzed caterpillars for their larval offspring.
Euodynerus hidalgo viereckii
A subspecies of mason wasp in the subfamily Eumeninae, Euodynerus hidalgo viereckii is one of three subspecies of the widespread species E. hidalgo. The species ranges across the United States from coast to coast, with this subspecies occurring in the western portion of the range. Females nest in pre-existing cavities including abandoned nests of other wasps and old solitary bee burrows, provisioning cells with paralyzed caterpillars.
Heriades
Armored Resin bees
Heriades is a genus of solitary bees in the family Megachilidae, comprising more than 130 species worldwide. These small, typically black bees are notable for nesting in pre-existing wood cavities and using plant resin to construct and seal nest cells. The genus spans eight subgenera with distributions across all continents; in North America, roughly 25 species occur, though only three are native east of the Rocky Mountains. Several species, particularly Heriades truncorum, serve as important research models for studying bee sexual communication, urban ecology, and pesticide effects.
Heriades carinata
Carinate Sculptured Mason Bee, Carinate Armored-Resin bee
Heriades carinata is a small solitary mason bee in the family Megachilidae. It is a twig-nesting species that uses pre-existing cavities such as hollow stems or beetle borings in dead wood. The female constructs nest cells separated by partitions of plant resin, earning it the common name 'Armored-Resin bee.' It has been recorded as the first gynandromorph in its genus. The species occurs across the United States and southern Canada.
Hoplitis anthocopoides
Viper's Bugloss Small-Mason
Hoplitis anthocopoides is a solitary mason bee in the family Megachilidae. It is a specialist pollinator of Echium vulgare (viper's bugloss), using this plant for both pollen/nectar collection and leaf material for nest construction. Females construct nests in pre-existing cavities using cut leaf pieces, creating linear series of 6-10 cells. Males exhibit territorial behavior, defending flower patches to gain access to females. The species has a broad distribution across Africa, Europe, Northern Asia (excluding China), and North America.
Hoplitis biscutellae
Creosote Small-Mason
Hoplitis biscutellae is a solitary mason bee in the family Megachilidae, first described by Cockerell in 1897. It is distributed across Central America and North America. Like other members of the genus Hoplitis, it is a cavity-nesting bee that constructs nests using mud or plant materials. The common name "Creosote Small-Mason" suggests an association with creosote bush (Larrea tridentata), though specific host plant relationships remain poorly documented.
Hoplitis fulgida platyura
Pacific Green Small-Mason
Hoplitis fulgida platyura is a subspecies of mason bee in the family Megachilidae. It is native to western North America, where it occurs from British Columbia to California. The subspecies is distinguished from the nominate form by structural differences in the male antennae and subtle coloration differences. Like other members of the genus Hoplitis, females construct nests in pre-existing cavities and line brood cells with collected materials.
Hylaeus affinis
eastern masked bee
Hylaeus affinis, commonly known as the eastern masked bee, is a small solitary bee in the family Colletidae. It is native to North America and belongs to the genus Hylaeus, whose members are often called masked bees or yellow-faced bees due to their distinctive facial markings. Like other Hylaeus species, it is nearly hairless and resembles small wasps in appearance. The species nests in pre-existing cavities and transports pollen and nectar internally rather than on body hairs.
Hylaeus basalis
Cinquefoil Masked Bee
Hylaeus basalis is a solitary bee species in the family Colletidae, commonly known as the Cinquefoil Masked Bee. It is native to North America and belongs to the genus Hylaeus, a group of nearly hairless bees often mistaken for wasps. Like other masked bees, females lack pollen-carrying structures and instead transport nectar and pollen internally in a crop, regurgitating food stores at the nest. The species has been documented in Colorado and Vermont.
Hylaeus communis
Common Masked Bee
Hylaeus communis is a small, nearly hairless solitary bee native to the Palearctic region and recently introduced to North America. It is one of the most common and adaptable species in its genus, exhibiting extreme generalism in habitat use and floral visitation. Females transport nectar and pollen internally in a crop, rather than on body hairs, and nest in pre-existing cavities. The species is partially bivoltine with flight activity from late May through September.
Hylaeus episcopalis
Episcopal Masked Bee
Hylaeus episcopalis is a species of masked bee in the family Colletidae, first described by Cockerell in 1896. Like other members of its genus, it is a solitary, nearly hairless bee that transports pollen and nectar internally rather than on body hairs. The species occurs in North America and is one of approximately 50 Hylaeus species on the continent. Four subspecies have been described: H. e. coquilletti, H. e. episcopalis, H. e. giffardiellus, and H. e. metzi.
Hylaeus floridanus
Florida Masked Bee
Hylaeus floridanus is a species of masked bee (yellow-faced bee) in the family Colletidae. Like other members of its genus, it is nearly hairless and wasp-like in appearance, transporting pollen and nectar internally in a crop rather than externally on body hairs. Females nest in pre-existing cavities such as hollow stems or twigs, lining cells with a secreted polymer. The species is native to Florida and the southeastern United States.
Hylaeus mesillae cressoni
Cresson's Masked Bee
Hylaeus mesillae cressoni is a subspecies of masked bee in the family Colletidae. Like other members of the genus Hylaeus, it is nearly hairless and often mistaken for a small wasp. The species is distributed in North America and Middle America. As a solitary bee, each female constructs her own nest in pre-existing cavities such as hollow stems or twigs.
Hylaeus modestus
modest masked bee, yellow-faced bee
A small, nearly hairless solitary bee in the family Colletidae, native to North America. Females transport pollen and nectar internally in a crop, then regurgitate it into brood cells lined with a secreted polymer. The species has been observed visiting annual flowers in garden settings and is a generalist forager. A gynandromorph specimen with bilaterally asymmetric male and female characteristics was documented from Ontario, Canada.
Hylaeus modestus citrinifrons
Modest masked bee
Hylaeus modestus citrinifrons is a subspecies of the modest masked bee, a small, nearly hairless solitary bee in the family Colletidae. It is part of a genus commonly known as yellow-faced or masked bees due to distinctive facial markings. The species H. modestus has been documented visiting flowers in garden and agricultural settings. Like other Hylaeus, it is a cavity-nesting bee that uses pre-existing hollow stems or twigs rather than excavating its own burrows.
Hylaeus polifolii
Buckwheat Masked Bee
Hylaeus polifolii is a solitary bee species in the family Colletidae, commonly known as the buckwheat masked bee. It is native to North America and belongs to the genus Hylaeus, a group of nearly hairless bees often mistaken for wasps due to their slender appearance. The species has two recognized subspecies: H. p. catalinensis and H. p. polifolii. Like other masked bees, females transport pollen and nectar internally in a crop rather than on body hairs.
Hylaeus punctatus
Punctate Masked Bee, Punctate Spatulate-Masked Bee
Hylaeus punctatus is a species of masked bee in the family Colletidae, native to North America. Like other members of its genus, it is nearly hairless and wasp-like in appearance, with distinctive facial markings. This solitary bee nests in pre-existing cavities such as hollow stems or twigs, lining cells with a glandular secretion. It is a generalist pollinator that transports pollen and nectar internally rather than on body hairs.
Hylaeus verticalis
Vertical Masked Bee
Hylaeus verticalis, commonly known as the Vertical Masked Bee, is a species of solitary bee in the family Colletidae. It is native to North America and belongs to the genus Hylaeus, a group of nearly hairless bees often mistaken for wasps due to their appearance. Like other masked bees, females carry pollen and nectar internally in a crop rather than on body hairs, and nest in pre-existing cavities such as hollow stems or twigs.
Isodontia
Grass-carrying Wasps, Grass-carrier Wasps
Isodontia is a genus of solitary wasps in the family Sphecidae, commonly known as grass-carrying wasps. Females construct nests in pre-existing cavities such as hollow stems, window tracks, or abandoned beetle tunnels, lining them with dry grass or hay. They provision nests with paralyzed Orthoptera (tree crickets and katydids) as food for their larvae. Several species are invasive in Europe, with Isodontia mexicana being the most widespread non-native species.
Isodontia auripes
Brown-legged Grass-carrier Wasp, brown-legged grass-carrier
Isodontia auripes, the brown-legged grass-carrier wasp, is a solitary thread-waisted wasp in the family Sphecidae. The species is known for its distinctive nesting behavior: females construct nests in pre-existing cavities such as window tracks, wind chimes, or abandoned carpenter bee tunnels, filling them with dry grass and provisioning them with paralyzed tree crickets (Oecanthus spp.) as food for their larvae. The wasp is non-aggressive toward humans and has been observed using nests made by Xylocopa virginica or mining bees. Larvae feed for approximately three days before pupating for two days.