Cavity-nester
Guides
Stenodynerus anormis
Mason wasp
Stenodynerus anormis is a solitary mason wasp in the subfamily Eumeninae. The species is difficult to distinguish from the related genus Parancistrocerus based on live specimens or photographs; microscopic examination of actual specimens is often required for positive identification. Females are known to provision nest cavities with paralyzed caterpillars as food for their larval offspring. The species has been documented utilizing artificial nesting structures such as bee blocks.
Stenodynerus blandoides
Stenodynerus blandoides is a species of solitary mason wasp in the subfamily Eumeninae, described by Bohart in 1943. It is a small, cavity-nesting wasp that provision nests with paralyzed caterpillars for its larval offspring. The species is difficult to distinguish from closely related genera such as Parancistrocerus based on live specimens alone. Like other eumenine wasps, it utilizes pre-existing tunnels in wood or hollow stems for nesting.
Stenodynerus blandus
Stenodynerus blandus is a species of mason wasp in the family Vespidae, subfamily Eumeninae. It is a small, solitary, cavity-nesting wasp that provisionally places paralyzed caterpillars in pre-existing cavities for its larval offspring. The species is difficult to distinguish from the closely related genus Parancistrocerus based on external morphology alone, often requiring microscopic examination for definitive identification. It has been documented utilizing artificial nesting structures such as bee blocks.
Stenodynerus blepharus
Stenodynerus blepharus is a species of solitary mason wasp in the subfamily Eumeninae, described by Bohart in 1953. The species is currently treated as a synonym of Rhynchalastor blepharus in some taxonomic databases, reflecting ongoing taxonomic revision in this group. As with other Stenodynerus species, it is presumed to be a cavity-nesting wasp that provisions its larvae with paralyzed caterpillars. Direct observations of this specific species in the field are sparse, with only two observations recorded in iNaturalist.
Stenodynerus fundatiformis
A small solitary mason wasp in the subfamily Eumeninae. The species is difficult to distinguish from related genera such as Parancistrocerus based on live specimens alone; microscopic examination is typically required for definitive identification. Females are known to provision nests with paralyzed caterpillars for their larval offspring. Males have been observed foraging on flowers, with the last antennal segment characteristically folded against the adjacent segment.
Stenodynerus histrionalis
Stenodynerus histrionalis is a solitary mason wasp in the subfamily Eumeninae, native to western North America. The species is difficult to distinguish from similar genera such as Parancistrocerus based on external morphology alone, often requiring microscopic examination of specimens. Females are known to provision nests with paralyzed caterpillars as food for their larvae. Males possess a distinctive antennal modification: the last segment is folded like a finger against the adjacent segment.
Stenodynerus histrionalis paenevagus
Stenodynerus histrionalis paenevagus is a subspecies of solitary mason wasp in the family Vespidae, subfamily Eumeninae. Like other Stenodynerus species, it is a cavity-nesting wasp that provisions its nests with paralyzed caterpillars as food for its larval offspring. The subspecies is difficult to distinguish from related taxa based on field observations alone, and microscopic examination is typically required for definitive identification. It has been documented in Colorado and California, where it utilizes pre-existing cavities in wood or other substrates for nesting.
Stenodynerus lucidus
Stenodynerus lucidus is a small solitary mason wasp in the subfamily Eumeninae. The species was described by Rohwer in 1917 and is currently considered a synonym of Rhynchalastor lucidus by some taxonomic authorities, though it remains listed under Stenodynerus in other sources. Like other eumenine wasps, it nests in pre-existing cavities and provisions its cells with paralyzed caterpillars as food for its larvae.
Stenodynerus microstictus
Stenodynerus microstictus is a solitary mason wasp in the subfamily Eumeninae. The species is difficult to distinguish from closely related genera such as Parancistrocerus based on external appearance alone. Females are known to provision nests with paralyzed caterpillars as food for their larvae. The species has been documented in western North America, including Colorado and California.
Stenodynerus ochrogonius
A solitary mason wasp in the subfamily Eumeninae, originally described by Bohart in 1944. Currently treated as a synonym of Rhynchalastor ochrogonius in some taxonomic databases, though iNaturalist and other sources maintain it under Stenodynerus. Like other eumenine wasps, females are predatory on caterpillars, which they paralyze and provision in nest cells for their larval offspring. Males have a distinctive antennal modification with the last segment folded like a finger against the adjacent segment. The species has been documented in Colorado and California.
Stenodynerus taosoides
Stenodynerus taosoides is a species of mason wasp in the subfamily Eumeninae (family Vespidae). Members of the genus Stenodynerus are solitary wasps that construct nests in pre-existing cavities, provisioning them with paralyzed caterpillars as food for their larval offspring. The species name suggests a connection to the Taos region of northern New Mexico, though specific details about its distribution and biology remain poorly documented in the available literature.
Symmorphus
mason wasps, potter wasps
Symmorphus is a genus of solitary mason wasps in the subfamily Eumeninae, distributed primarily across the Holarctic region with 36 recognized species. These small wasps (6–20 mm) are cavity-nesters that utilize pre-existing holes in wood, hollow stems, or twigs, partitioning them into multiple cells with mud walls. Females are predators that mass-provision nests with paralyzed larvae of leaf beetles (Chrysomelidae), weevils (Curculionidae), or leaf-mining moth caterpillars. The genus occupies a relatively isolated phylogenetic position within Eumeninae and includes two subgenera: S. (Symmorphus) and S. (Parasymmorphus).
Symmorphus albomarginatus
White-bordered Potter Wasp
A small, slender mason wasp in the subfamily Eumeninae. Females construct multi-celled nests in pre-existing wood cavities, provisioning cells with paralyzed leaf beetle larvae (Chrysomelidae), weevil larvae (Curculionidae), or leaf-mining moth caterpillars. Two subspecies recognized: nominate S. a. albomarginatus and S. a. midas from southern Texas. The species ranges across much of North America from Alaska to California and eastward.
Symmorphus canadensis
Canadian potter wasp, Canadian mason wasp
Symmorphus canadensis is the smallest North American species in the genus Symmorphus, measuring approximately 6–10 mm. This solitary mason wasp specializes in hunting leaf beetle larvae, weevil larvae, and leaf-mining moth caterpillars to provision nests constructed in pre-existing cavities. Females partition nest tunnels into multiple cells using mud partitions, laying one egg per cell atop paralyzed prey. The species is transcontinental across North America, absent only from Florida, Texas, New Mexico, and Arizona.
Symmorphus projectus
Symmorphus projectus is a small, slender mason wasp in the subfamily Eumeninae. It is strictly western in distribution, ranging from the Pacific Northwest to Montana, Wyoming, and southward. Females nest in pre-existing cavities such as beetle borings in dead wood, provisioning cells with paralyzed leaf beetle larvae, weevil larvae, or leaf-mining moth caterpillars for their offspring. The species is one of four Symmorphus species in North America and can be distinguished from eastern congeners by geographic range and subtle morphological features.
Temnothorax longispinosus
Long-spined Acorn Ant
Temnothorax longispinosus is a small North American ant species, measuring 2–2.5 mm in length, commonly known as the Long-spined Acorn Ant. It inhabits forest environments and nests primarily in preformed cavities within leaf litter, including hollow nuts and acorns. The species exhibits remarkable queen polymorphism with three distinct morphs associated with alternative nest-founding strategies: small queens with reduced flight capacity that practice dependent colony founding by returning to natal nests; large queens with low fat reserves that found colonies via pleometrosis (cooperative founding with multiple queens); and large queens with high fat reserves that practice haplometrosis (solitary founding). This species serves as a host for the slave-making ant Protomognathus americanus and has been extensively studied for its genomic adaptations to climate variation and parasite pressure.
Trypoxylon
keyhole wasps, pipe organ mud daubers
Trypoxylon is a large genus of solitary wasps in the family Crabronidae, comprising approximately 634 species worldwide. The genus is notable for being the most speciose within its family. All studied species are active hunters of spiders, which they paralyze with venom to provision nests for their larvae. Nesting strategies vary: most species utilize pre-existing cavities such as hollow stems, beetle borings, or abandoned nests, while a minority construct free-standing mud nests. The genus is divided into two subgenera: Trypoxylon (smaller species) and Trypargilum (medium to large species).
Trypoxylon californicum
Trypoxylon californicum is a solitary spider-hunting wasp in the family Crabronidae, subgenus Trypargilum. Females nest in pre-existing cavities such as hollow twigs, beetle borings, or abandoned mud dauber nests, partitioning them into multiple cells provisioned with paralyzed spiders. Males actively guard nest entrances against parasites while females hunt, a behavior termed 'patriarchate' by naturalists. The species is found across western North America and has been successfully attracted to artificial trap nests.
Trypoxylon carinatum
Trypoxylon carinatum is a species of solitary spider-hunting wasp in the family Crabronidae. As a member of the subgenus Trypargilum, it is among the larger species in the genus. Like other Trypoxylon, females nest in pre-existing cavities and provision cells with paralyzed spiders for their offspring. The species is distributed across North America and Middle America.
Trypoxylon clavatum
square-headed wasp
Trypoxylon clavatum is a species of square-headed wasp in the family Crabronidae, found in North America. It belongs to the subgenus Trypargilum, which includes medium-sized and larger species in this genus. The species has two recognized subspecies: T. c. clavatum and T. c. johannis. Like other Trypoxylon species, it is a solitary spider-hunting wasp that nests in pre-existing cavities.
Trypoxylon clavatum clavatum
Trypoxylon clavatum clavatum is a subspecies of spider-hunting wasp in the family Crabronidae. It belongs to the subgenus Trypargilum, characterized by medium to large body size within the genus. The wasp nests in pre-existing cavities such as hollow twigs, beetle borings, and abandoned mud dauber nests, provisioning cells with paralyzed spiders for its larvae. Males actively participate in nest guarding and maintenance, a behavior termed 'patriarchate' by naturalist Phil Rau.
Trypoxylon frigidum
Trypoxylon frigidum is a species of square-headed wasp in the family Crabronidae. It is found in North America. The species belongs to the subgenus Trypoxylon, characterized by small body size compared to the larger subgenus Trypargilum. Two subspecies are recognized: T. f. frigidum and T. f. cornutum.
Trypoxylon spinosum
Black Reed Wasp
Trypoxylon spinosum is a species of solitary spider-hunting wasp in the family Crabronidae. As a member of the subgenus Trypargilum, it is among the larger-bodied species in the genus. Like other Trypoxylon wasps, it nests in pre-existing cavities and provisions cells with paralyzed spiders for its offspring. The species was described by Cameron in 1889 and is known from Middle and North America.
Trypoxylon tridentatum
Trypoxylon tridentatum is a spider-hunting wasp in the family Crabronidae, subgenus Trypargilum. It inhabits mesic and xeric habitats in arid regions, particularly the Baja California peninsula. The wasp provisions nest cells with paralyzed spiders as food for its larvae, showing strong preference for orb-weaving spiders in the family Araneidae. Unlike its congener T. politum, which constructs free-standing mud nests, T. tridentatum nests in pre-existing cavities such as hollow twigs, beetle borings, and abandoned mud dauber nests.
Trypoxylon tridentatum archboldi
Trypoxylon tridentatum archboldi is a subspecies of spider-hunting wasp in the family Crabronidae. As a member of the subgenus Trypargilum, it belongs to a group of medium-sized to large Trypoxylon species that nest in pre-existing cavities rather than constructing free-standing mud nests. The species was described by Krombein in 1959 and is known from North America, with records from British Columbia, Canada. Like other Trypargilum species, it likely exhibits cooperative nesting behavior with males participating in nest guarding and maintenance, though specific behavioral documentation for this subspecies is limited.
Trypoxylon tridentatum tridentatum
Trypoxylon tridentatum tridentatum is a spider-hunting wasp in the family Crabronidae, subgenus Trypargilum. It occurs in mesic and xeric habitats of the arid Baja California peninsula and has been documented in British Columbia, Canada. This subspecies provisions nest cells with paralyzed spiders, with Araneidae comprising the majority of prey.
Vespa crabro
European hornet
The European hornet (Vespa crabro) is the largest true hornet native to Europe and the only established Vespa species in North America. Introduced to the eastern United States in the mid-1800s, it has spread west to the Rocky Mountains. This eusocial wasp constructs paper nests in enclosed cavities such as hollow trees, wall voids, and abandoned beehives. Unlike many social wasps, it exhibits nocturnal foraging behavior and is attracted to light. While capable of delivering painful stings when nests are disturbed, it is generally less aggressive toward humans than yellowjackets and is not considered a major threat to honey bee colonies.
Vespula germanica
German yellowjacket, European wasp, German wasp
Vespula germanica is a highly invasive social wasp native to Europe, Northern Africa, and temperate Asia that has established populations across much of the Northern Hemisphere and Southern Hemisphere, including North America, South America, Australia, New Zealand, and South Africa. It is one of the most successful invasive wasp species globally, characterized by exceptional cognitive flexibility, opportunistic foraging behavior, and adaptability to diverse environments. The species exhibits complex social organization with annual colonies founded by single queens, though perennial colonies occur in favorable climates. Its invasive success is attributed to flexible nesting habits, broad dietary range, and efficient resource exploitation, though human-aided transport of hibernating queens significantly contributes to long-distance dispersal.