Symmorphus projectus
Bohart, 1950
Symmorphus projectus is a small, slender in the 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 borings in dead wood, provisioning with paralyzed , larvae, or leaf-mining for their offspring. The is one of four Symmorphus species in North America and can be distinguished from eastern by geographic range and subtle morphological features.
Pronunciation
How to pronounce Symmorphus projectus: //sɪˈmɔrfəs proʊˈdʒɛktəs//
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Identification
Distinguished from other North Symmorphus primarily by geographic distribution: strictly western from Pacific Northwest to Montana, Wyoming, and southward, whereas S. albomarginatus, S. canadensis, and S. cristatus are more widespread or eastern. From S. canadensis (smallest species) by larger size. From S. cristatus and S. albomarginatus by range. Generic characters include horizontal and vertical groove on first abdominal tergite, and simple last antennal in males. Specific diagnostic features for S. projectus within the are not detailed in available sources.
Habitat
Found in association with dead, standing or fallen trees with borings, particularly those made by deathwatch beetles ( , formerly ). Uses pre-existing wood cavities including beetle exit holes in dead cottonwoods and other trees, hollow twigs, or stems. Nests in shaded locations or on the shady side of trees. Readily uses artificial nest blocks with holes 3-4 mm in diameter placed in sheltered situations such as under eaves or in firewood stacks.
Distribution
Strictly western North America: Pacific Northwest (Washington, Oregon, British Columbia) eastward to Montana and Wyoming, and southward (California, Nevada, Utah, Colorado, Arizona, New Mexico). Not found in eastern North America where S. albomarginatus, S. canadensis, and S. cristatus occur.
Diet
feed on (sweet liquid waste secreted by ). Females provision nests with paralyzed of (), (), or leaf-mining as food for offspring.
Host Associations
- leaf beetles - paralyzed and stored as food for offspring
- weevils - paralyzed and stored as food for offspring
- leaf-mining moths - occasionally taken; primarily leaf-mining
- aphids - food source for consume secreted by
- deathwatch beetles - nest site provideruses exit holes made by emerging in (formerly )
Life Cycle
Females use pre-existing cavities in wood, hollow twigs, or stems. They partition tunnels into multiple using mud curtains, working from back to . Each cell receives one , then is provisioned with paralyzed . Number of prey per cell depends on prey size and offspring sex (female larvae require more food). Completed nests typically contain multiple cells; often includes an empty 'vestibular' cell at entrance and sometimes 'intercalary' vacant cells between provisioned cells, possibly as defense against . One 7-cell nest of congeneric S. canadensis was completed in about three days. Developmental timing not specified for S. projectus specifically.
Behavior
Solitary nesting . Females hunt , paralyze it with , and transport to nest. They modify pre-existing cavities by chewing wood fibers to expand entrances or plastering with mud/resin to shrink them, though prefer holes that fit without modification. Females can control offspring sex through . Males harass females for mating opportunities; multiple males may compete, causing females to tumble from nest entrances. frequently visit colonies to feed on .
Ecological Role
of , larvae, and leaf-mining , helping to control of these that can defoliate trees and shrubs. specialization makes it a targeted agent in its . Serves as for parasitic (), eulophid (Melittobia), wasps (Monodontomerus), and satellite (Amobia), contributing to complexity. Nest cavities used after abandonment may provide habitat for other organisms.
Human Relevance
that helps control and in gardens, orchards, and forests. Readily accepts artificial nest blocks (' condos'), making it accessible for citizen science observation and backyard . Does not humans unless handled. Not a —does not create its own holes in wood, only uses pre-existing cavities. Can be encouraged by preserving dead standing trees or installing wooden blocks with 3-4 mm holes in sheltered locations.
Similar Taxa
- Symmorphus cristatusOverlaps in western range; distinguished by broader transcontinental distribution extending eastward, and subtle morphological differences not detailed in sources.
- Symmorphus canadensisOverlaps in western range; distinguished by smaller size (smallest North Symmorphus) and broader transcontinental distribution except Florida, Texas, New Mexico, and Arizona.
- Symmorphus albomarginatusDistinguished by range—found from Alaska to California, New Mexico, Quebec, and eastern U.S., not strictly western.
- Trypoxylon spp.Co-occurs in borings; distinguished by extremely slender 'thread-waisted' body form, different ( rather than beetle ), and different nest closure (typically plugs with mud rather than partitioning ).
- Passaloecus spp.Co-occurs in borings; smaller with different (aphids rather than beetle ) and different body proportions.
More Details
Nest parasitism
Nests are frequently parasitized by ( ), which lay in nests where their consume the provisioned . Other documented include eulophid ( Melittobia, family ), wasps (genus Monodontomerus), and satellite (genus Amobia, family ). Nests may also be infested by Grain Itch (Pyemotes ventricosus) or scavenged by (family ) and (family ).
Artificial nesting
Will use holes drilled in wooden blocks, 3-4 mm in diameter and up to six inches deep, placed in sheltered locations. This makes the amenable to study through trap-nesting programs.