Dianthidium pudicum

Dianthidium pudicum can be distinguished from other Dianthidium species by subtle morphological features, including the specific pattern and extent of pale markings on the body. Within its geographic range, it may be confused with other small megachilid bees such as Heriades or Osmia species. Examination of diagnostic characters including the shape of the clypeus, the structure of the mandibles, and the specific pattern of punctation on the terga is typically required for definitive identification. The species is smaller than some congeners and exhibits relatively modest pale markings, consistent with its common name.

As a member of the genus Dianthidium, this species exhibits the typical morphology of resin bees: a compact, somewhat stout body with a broad abdomen. The integument is generally dark with pale or yellowish maculations. Females possess a scopa (pollen-collecting structure) on the underside of the abdomen rather than on the hind legs. The body is moderately hairy, with denser hair on the ventral surface of the abdomen in females for pollen transport.

This species occupies a variety of open habitats including grasslands, prairies, and open woodlands. It has been documented nesting in bee blocks and artificial nesting structures, indicating adaptability to human-modified environments. The species requires access to suitable nesting substrates—typically pre-existing cavities such as hollow twigs, beetle borings in dead wood, or artificial tunnels—and sources of resin for nest construction.

Dianthidium pudicum is native to North America, with records from the central and western United States. Specific documented localities include Colorado and surrounding regions. The species' range extends through the Great Plains and into the western United States, though precise distributional boundaries remain incompletely documented.

Adult activity has been recorded during the summer months, with observations from June in Colorado. As with other Dianthidium species, the flight period likely extends from late spring through mid-summer, with exact timing varying by latitude and elevation.

Females utilize pre-existing cavities such as hollow twigs, beetle borings in dead wood, or artificial tunnels in bee blocks for nesting. They construct individual cells within these cavities, partitioning them with walls made of collected resin. Each cell is provisioned with a pollen-nectar mixture (bee bread) before an egg is laid. The larva consumes the provision, spins a cocoon, and pupates within the cell. Development time from egg to adult is approximately several weeks under favorable conditions, with some individuals potentially entering diapause to overwinter as prepupae or pupae.

This is a solitary bee species with no social organization. Females are responsible for all nest construction, provisioning, and oviposition. They collect resin from plant sources to construct cell partitions and nest plugs. The species has been observed nesting in aggregations when suitable nesting sites are abundant. Males are typically smaller than females and do not participate in nest construction or provisioning.

As a solitary bee, D. pudicum serves as a pollinator of flowering plants within its habitat. Its specific floral associations are not well documented, but like other Dianthidium species, it likely visits a variety of open flowers. The species also serves as a host for parasitic wasps, including leucospid wasps in the family Leucospidae, which are known to parasitize megachilid bees.

This species has been documented utilizing artificial bee blocks or bee hotels, indicating its value as a subject for native bee conservation and citizen science monitoring. Its presence in urban and suburban environments demonstrates the potential for providing artificial nesting structures to support native pollinator populations. The species contributes to pollination services in both natural and human-modified landscapes.

• Dianthidium (Dianthidium) spp.Other species in the subgenus Dianthidium share similar morphology and nesting habits, requiring careful examination of specific diagnostic characters for separation.
• Heriades spp.These small megachilid bees also nest in pre-existing cavities and use resin for nest construction, though they typically have more elongate bodies and different facial markings.
• Osmia spp.Mason bees in this genus are similar in size and nesting biology but typically use mud or chewed leaf material rather than resin for nest partitions.

• solitary bee
• resin bee
• native pollinator
• cavity nester
• bee hotel species

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
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