Pollinator Post 8/5/25
It’s a bright sunny morning at Crab Cove.
The Sneezeweed, Helenium puberulum is blooming profusely near the visitor center, the odd globular flowerheads on naked stalks waving in the breeze. It is amazing that insects can maintain their balance while they forage on the tiny florets that open in bands across the surface of the flowerhead. Here, an American Sand Wasp, Bembix americana (family Crabronidae) is concentrating its efforts on the opened disc florets with bright yellow anther tubes. The immature florets in buds are purplish brown.
Sand wasps in the genus Bembix are familiar and common throughout North America, digging their burrows in dunes, on beaches, and other habitats with loose, deep sand. The female rapidly kicks out large quantities of sand using a “tarsal rake” of spines on each front leg. The burrow is excavated before the wasp goes hunting. Bembix are generalist, opportunistic hunters. True flies in the order Diptera are the usual prey. A victim is paralyzed or killed by the wasp’s sting, and is then flown back to the nest. Most species will lay an egg on the first victim, while some species lay an egg in the empty cell before starting to hunt. Once the egg hatches, mama wasp brings flies to her larva as needed. This “progressive provisioning” is rare in the insect world. When the larva reaches maturity, mama wasp closes the cell. Inside, the larva spins an oblong cocoon, weaving sand grains into the structure and resulting in a hardened capsule. Overwintering takes place as a prepupa inside this cocoon, but there are usually two generations a year.
Male sand wasps often engage in an elaborate flight ritual called “sun dances”. Males emerge before females, and fly erratically at dizzying speed one or two inches above the ground attempting to detect virgin females about to emerge from their underground nests. Both sexes are often seen taking nectar at flowers, especially from Asteraceae family. Bembix wasps are often victims of other insects such as cuckoo wasps (Chrysididae), velvet ants (Mutillidae), satellite flies (Sarcophagidae), bee flies (Bombyliidae), and thick-headed flies (Conopidae).
An Inchworm caterpillar of the Common Eupithecia Moth, Eupithecia miserulata (family Geometridae) is sprawled on an older Sneezeweed flowerhead that is no longer offering any pollen.
Inchworms are also called loopers and measuring worms. They majority of the inchworms are the larvae of moths in the family Geometridae. The name comes from the Greek “geo” for earth and “metro” from measure, because the caterpillars seem to be measuring the surface on which they are walking. Most caterpillars have five sets of prolegs, four in the middle of the body and one pair at the hind end. Inchworms have the normal six true legs but only two or three pairs of prolegs, all located at the tail end of the body, with none in the middle. When an inchworm walks, it moves its tail-end prolegs up behind its true legs, causing the center of its body to loop upward. Then it stretches its front end forward to take another step.
Eupithelia is the largest genus of moths of the family Geometridae. Occurring worldwide except for Australasia, species in the genus are commonly known as pugs. Adults are typically small, 12 – 35 mm, with muted colors. Most species rest with forewings held flat at right angles to the body, while the hindwing are largely covered by the forewings. They are generally nocturnal. Larvae mostly feed from the flowers and seeds of their food plants rather than the foliage. Many species have a very specific food plant.
Eupithecia miserulata, the Common Eupithecia Moth is found in North America. The adult wingspan is 12-20 mm. The larvae feed on a wide range of plants, including coneflower, asters, willow, cherry, juniper and clover.
That looks like a silken cocoon on an immature Sneezeweed flowerhead. Did an Eupithecia caterpillar make this? Most Eupithecia caterpillars pupate in the soil or leaf litter, rather than forming a visible silken cocoon. The cocoon looks suspiciously like that of a Braconid wasp. See the blunt end of the cocoon? The parasitoid wasp has already cut opened the cocoon to emerge as an adult. Wow! I often find Braconid cocoons like this next to dead Anise Swallowtail caterpillars.
Braconid Wasps (family Broconiade) are one of the greatest parasitoids, responsible for many moth and butterfly deaths. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species. Females often have long ovipositors to lay eggs on or in their hosts. The larvae of most braconids are internal primary parasitoids of other insects, especially the larval stages of Coleoptera, Diptera, and Lepidoptera. Generally, the braconid life cycle begins when the female wasp deposits her eggs in the host insect, and the braconid larvae develop in the host body, eating it from the inside out. Before the caterpillar is ready to pupate, Braconid wasp larvae will exit the caterpillar, and immediately weave their cocoons, often on or next to the host. The adult braconid wasp emerges by cutting a hole on one side of the cocoon and begins the life cycle again.
Braconid wasps use a remarkable weapon to disable the defenses of their host insects – a virus. These parasitic wasps coevolved with polydnaviruses (read poly-DNA-virus), which they carry and inject into the host insects along with their eggs. The virus attacks the host’s immune system and renders it unable to encapsulate the wasp egg; it also halts the host’s development, so it can’t pupate and transform into an adult. Amazingly, the “bracovirus” also changes the host’s metabolism so that it can survive longer without food or water – thus ensuring a nurturing environment for all the young wasps to come.
A female Fine Striped Sweat Bee, Agapostemon subtilior (family Halictidae) forages on a Sneezeweed flowerhead. She is going around the flowerhead taking nectar from the band of opened florets.
The genus Agapostemon is widespread and abundant throughout North America. They are most diverse and abundant in temperate regions and southwestern U.S. deserts. Agapostemon are commonly called “sweat bees” because they are closely related to, and resemble bees in the Halictus and Lasioglossum genera. Unlike those bees however, Agapostemon are not attracted to human sweat.
Agapostemon are brightly colored metallic green or blue bees measuring 7 to 14.5 mm long. Most species have a metallic green head and thorax, and black-and-yellow striped abdomen; some females are entirely bright green or blue. Females carry pollen on scopal hairs located on their hind legs. Agapostemon are ground-nesters and generalist foragers. Like other members of the family Halictidae, they are short-tongued and thus have difficulty extracting nectar from deep flowers. Males are often seen flying slowly around flowers looking for females. The bees favor flowers with high densities. They are active summer through fall.
Agapostemon females dig deep vertical burrows in flat or sloping soil, or sometimes in banks. Most species are solitary, but some species nest communally. Up to two dozen females may share a single nest entrance, but each individual builds and provisions its own cluster of brood cells. Where a communal nest gallery shares a single entrance, one bee usually guards the hole, with only her head visible from above ground. Unlike other social bees, in communal bees there is no reproductive division of labor. In cool temperate regions, there is one generation per year, with females active in the early summer and males and pre-diapausing females active in the late summer. Only mated females survive the winter. This is probably because unmated females cannot enter diapause (insect version of hibernation).
I then decide to explore the narrow strip of land enclosing Ballena Bay that is shored up with concrete rubble. The barren, artificial landscape has never attracted me in the past…
….but the Oregon Gumweed, Grindelia stricta blooming along the edges is beckoning to me.
Hey, that’s a Cuckoo Bee, Complex Nomada vegana (family Apidae) on that Grindelia flowerhead. That’s a good sign. Cuckoo bees don’t exist in isolation – their presence usually indicates a healthy population of their host bees!
Nomad Bees in the genus Nomada is one of the largest genera in the family Apidae, and the largest genus of Cuckoo Bees. Nomada are kleptoparasites of many different types of ground-nesting bees as hosts, primarily the genus Andrena. They lack a pollen-carrying scopa, and are mostly hairless, as they do not collect pollen to feed their offspring. Adults visit flowers for nectar. The bees are extraordinarily wasp-like in appearance, often with yellow or white integumental markings on their abdomen.
Nomad Bees occur worldwide. All known species parasitize ground-nesting bees, and their habitats and seasonality correlate closely with their hosts. In early spring, females scout out their hosts, searching for nests to parasitize. The female Nomada sneaks into the host’s nest while the resident female is out foraging, then lays eggs in the nest. The parasite larva that hatches out kills the host offspring and feeds on the host’s provisions. This type of parasitism is termed brood parasitism. The parasites pupate in the host cell and finally emerge as adults the following season along with the hosts.
While we might shudder at the thought of cuckoo bees in our garden, the presence of cuckoo bees actually indicates a healthy population of their host bees, suggesting a diverse and thriving ecosystem. Parasitism is a natural part of many ecosystems, and cuckoo bees play a role in regulating the populations of their host species. Cuckoo bees, while not collecting pollen for their own young, still visit flowers for nectar and inadvertently pollinate plants in the process. Cuckoo bees are also a food source for other animals, further contributing to the food web.
A female Fine Striped Sweat Bee, Agapostemon subtilior (family Halictidae) is foraging on a Grindelia flowerhead.
I am often amazed by the flexibility of the bee’s “neck” that allows them to forage so effectively. In bees and other insects, the “neck” generally refers to the narrow, flexible region that connects the head to the thorax, known as the cervix. This region allows for flexible movement of the head independently from the body, for tasks like foraging, navigation, and defense. The cervix contains various muscles (direct and indirect) that allow for a wide range of head movements, including rotation, flexion, extension, and retraction. It also houses mechanoreceptive hair cells that detect movement between the head and the prothorax, providing sensory feedback for controlled head movements.
Ooh, that adorable face! It is a Cellophane Bee, Colletes sp. (family Colletidae).
The bee family Colletidae includes generalists and specialists, and they are likely important pollinators of many wildflowers. All Colletidae in North America are solitary ground nesters, but some species nest in large aggregations. There are two major genera of Colletidae in North America: the Masked Bees (genus Hylaeus) and Cellophane Bees (genus Colletes). The most obvious shared characteristics of Colletidae is also the hardest to see: their short tongue. Colletes are moderately hairy, slender bees, ranging in size from 7 to 16 mm. Distinct features include a hairy head and thorax, pale bands of hair on the abdomen, and a heart-shaped head. The eyes of Colletes are angled (rather than being parallel), making the face slightly heart-shaped.
The genus name Colletes means “one who glues”, referring to their habit of applying a glue- or cellophane-like lining to the walls of nest cells, using their specialized tongues. This lining gives rise to their common names: cellophane bees, polyester bees, and plasterer bees. Colletes tongue is unique: short, flat, and forked at the tip. Colletes line their nests with a distinctive cellophane-like substance made from saliva and secretions from the Dufour’s gland on the abdomen. Using their specialized tongue, they paint the walls with saliva, then with secretions from the Dufour’s gland, they add a coat of varnish. This creates a clear covering that is strong, durable, and resistant to mold and water.
The Honey Bees, Apis mellifera (family Apidae) are the most commonly seen bees on the Grindelia flowers.
A Tripartite Sweat Bee, Halictus tripartitus (family Halictidae) is foraging on a Grindelia flowerhead.
Halictus is found worldwide; they are most common in the Northern Hemisphere. All are generalists, foraging from a wide variety of flowering plants. Many species are social and produce several generations per year. This is not surprising as most blooming plants are season-specific; a bee that requires pollen and nectar across multiple seasons would not thrive as a specialist. All Halictus in North America nest in the ground, often in aggregations; and they may nest in the same area for decades.
The species Halictus tripartitus is primitively eusocial, meaning it has a social structure that is less complex than highly social insects like honey bees, but more advanced than solitary bees. The bees form annual colonies in the soil, where some workers are capable of reproducing. Only potential queens overwinter, then provision a worker brood in the spring, with at least one worker brood produced before males and new queens emerge. These bees are known to nest in aggregations, often in flat, bare ground. They visit and pollinate a wide variety of flowers.
Many male Summer Longhorn Bees, Melissodes sp. (family Apidae) can be seen visiting the Grindelia flowerheads.
The Summer Longhorn Bees, Melissodes sp. (family Apidae) are medium to large bees, stout-bodied, usually with gray hair on the thorax and pale hair bands on the abdomen. Males usually have yellow markings on their faces and have very long antennae from which their common name is derived. They are active May to September, with peak flight in late June to early August. The females prefer flat, bare ground for digging their solitary nests, though they sometimes nest in aggregations. Pollen is transported in scopae on the hind legs. Pollen loads are often copious and brightly colored and thus very distinguishable. Melissodes are specialists on Asteraceae – females gather pollen from flowers of Aster, Bidens, Coreopsis, Cosmos, Encelia, Gaillardia, Helianthus, and Rudbeckia ssp.
A Small Carpenter Bee, Ceratina sp. (family Apidae) is collecting pollen from the opened florets on the periphery of a young Grindelia flowerhead.
The Small Carpenter Bee (genus Ceratina) is closely related to the more familiar, and much larger Carpenter Bees (genus Xylocopa). Ceratina are typically dark, shiny, even metallic bees, with fairly sparse body hairs and a weak scopa on the hind leg. The shield-shaped abdomen comes to a point at the tip. Some species have yellow markings, often on the face.
Females excavate nests with their mandibles in the pith of broken or burned plant twigs and stems. While many species are solitary, a number are subsocial. Both male and female carpenter bees overwinter as adults within their old nest tunnels, emerging in the spring to mate. In the spring, this resting place (hibernaculum) is modified into a brood nest by further excavation. The female collects pollen and nectar, places this mixture (called bee bread) inside the cavity, lays an egg on the provision, and then caps off the cell with chewed plant material. Several cells are constructed end to end in each plant stem.
An American Sand Wasp, Bembix americana (family Crabronidae) is foraging on a Grindelia flowerhead. It is not surprising that the sand wasps are so common here – the sandy soils on the upper beaches at Crab Cove are ideal nesting habitats for these wasps.
Sand wasps in the genus Bembix are familiar and common throughout North America, digging their burrows in dunes, on beaches, and other habitats with loose, deep sand. The female rapidly kicks out large quantities of sand using a “tarsal rake” of spines on each front leg. The burrow is excavated before the wasp goes hunting. Bembix are generalist, opportunistic hunters. True flies in the order Diptera are the usual prey. A victim is paralyzed or killed by the wasp’s sting, and is then flown back to the nest. Most species will lay an egg on the first victim, while some species lay an egg in the empty cell before starting to hunt. Once the egg hatches, mama wasp brings flies to her larva as needed. This “progressive provisioning” is rare in the insect world. When the larva reaches maturity, mama wasp closes the cell. Inside, the larva spins an oblong cocoon, weaving sand grains into the structure and resulting in a hardened capsule. Overwintering takes place as a prepupa inside this cocoon, but there are usually two generations a year.
Male sand wasps often engage in an elaborate flight ritual called “sun dances”. Males emerge before females, and fly erratically at dizzying speed one or two inches above the ground attempting to detect virgin females about to emerge from their underground nests. Both sexes are often seen taking nectar at flowers, especially from Asteraceae family. Bembix wasps are often victims of other insects such as cuckoo wasps (Chrysididae), velvet ants (Mutillidae), satellite flies (Sarcophagidae), bee flies (Bombyliidae), and thick-headed flies (Conopidae).
A female Western Leafcutter Bee, Megachile perihirta (family Megachilidae) has landed on a Grindelia flowerhead.
Leaf-cutter Bees, Megachile sp. (family Megachilidae) are stout-bodied, usually with pale hair on the thorax and stripes of white hairs on the abdomen. Females usually have a triangular abdomen with a pointed tip, and males’ faces are covered with dense, pale hair. Flight season is from May into September, with peak activity from June to August.
Solitary females construct nests in tubular cavities, including hollow stems, tree holes, and abandoned beetle burrows in wood. Many use holes drilled into wood, straws, or other manufactured tunnels. Females cut pieces from leaves or flower petals for use in the construction of brood cells. Most Megachile females are generalists when foraging for pollen. Pollen is transported in dense scopae on the underside of the abdomen.
Photos of Western Leafcutter Bee (Megachile perihirta) · iNaturalist
Her abdomen held high, the female Western Leafcutter Bee is collecting pollen and nectar. The rusty-red hairs of her abdominal scopae are already covered with yellow pollen.
North America is home to many leafcutter bees, but the Western Leafcutter, Megachile perihirta is one of the largest. The species ranges on the west coast from British Columbia south to northern Mexico. From a distance, the female can be mistaken for a honey bee. She is about the same size as a worker honey bee and enjoys many of the same flowers, but her head is disproportionately large because it houses the bulky muscles that operate her large mandibles. While most leafcutter bees nest above ground in tubes and tunnels, the Western Leafcutter nests underground. Often a small group of females live in a community and burrow into soil, gravel, or sand. The Western Leafcutters prefer flowers in the Asteracea family for nectar and pollen; the composite flowerheads offer a flat surface on which numerous florets are conveniently clustered. The bees are frequently seen foraging on Seaside Daisy, Grindelia, Asters, Sunflowers, Cosmos, and Dahlia.
Ooh, there’s a male Western Leafcutter Bee, Megachile perihirta (family Megachilidae). He is not as robustly built as the female, and his abdomen is not pointed but rounded.
The male Western Leafcutter Bee is covered with a dense fur coat, and there are long fringes hanging from his extra-wide forelegs. The male uses his hairy legs – the portion known as the tarsus – to cover the eyes of the female during copulation, probably to keep her calm and receptive. Like other male bees, he does not collect pollen. However, he does visit flowers for nectar, and often contributes to pollination.
