Pollinator Post 8/24/26 (1)
Since the Oregon Gumweed, Grindelia stricta started to bloom along the shoreline of Bay Farm, I have never had a dull moment on my walks here. One of the few native plants in this altered habitat that blooms while other floral resources have dwindled, it attracts a plethora of insects.
A female Western Leafcutter Bee, Megachile perihirta (family Megachilidae) has landed on a Grindelia flowerhead. Her abdomen held high, she gets into pollen-collecting mode right away. I never tire of photographing these charismatic and photogenic native bees .
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 generalist foragers, but prefer flowers in the family Asteraceae.
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.
Leafcutter bees (genus Megachile) carry pollen on a dense brush of stiff hairs on the underside of their abdomen, known as a scopa. As the bee flies, her fuzzy body builds up a positive static charge. When she lands on a flower, this static electricity pulls pollen grains from the anthers, causing them to cling all over her body. Rather than landing and simply walking around, leafcutter bees often dive directly onto the flower and raise their abdomen, rubbing their hairy underside aggressively against the flower’s reproductive parts. She uses a coordinated grooming motion to brush pollen off her body with her forelegs, passing it to her middle legs, and then uses her hind legs to rake and pack the pollen grains securely into the scopa on her belly. When she returns to her nesting cavity, she scrapes the pollen off her abdomen using her hind legs and mixes it with regurgitated nectar to form a nutrient-rich “bee bread” on which she lays an egg.
A male Western Leafcutter Bee, Megachile perihirta (family Megachilidae) is grooming himself on a Grindelia leaf.
All spiffed up, he visits a Grindelia flowerhead for nectar.
Perched on a ray petal, a small wasp is repeatedly extruding its complex mouthparts to clean them. Judging by its long antennae and small size, I gather it is probably a Braconid Wasp.
The Braconidae are a family of parasitoid wasps. 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. When the wasp larvae are ready to pupate, they may do so in or on the host insect. The new generation of adult braconid wasps emerges from their cocoons 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 tiny, shiny beetle is perched head-down on an anther tube of a Grindelia flower.
On an adjacent Grindelia flowerhead, a similar beetle is in clear view. It is a Bronze Leaf Beetle, Diachus auratus (family Chrysomelidae).
The Bronze Leaf Beetle, Diacus auratus (family Chrysomelidae) is a small, shiny, “bullet-shaped” beetle that feeds on the leaves, flowers, and fruits of plants, particularly berry crops such as strawberries, raspberies, and blackberries. It is a species of case-bearing leaf beetle in the subfamily Cryptocephalina, known for larvae that create cases out of feces and debris. The species is widespread in North America, as well as parts of Central and South America, Australia, and Asia. Adults, 1-2 mm, are found on many unrelated plants, especially plants in bloom. The larvae live underground and feed on the roots of plants, specifically grass and clover. As she lays her eggs, the female covers each one with a layer of excrement. After the larvae hatch, they retain this covering (case) as camouflage and add to it throughout their larval life. When disturbed, the larvae pull in their head and legs; because their color and shape resemble caterpillar droppings they are ignored by predators. Eventually the larva seals the case to pupate inside, before emerging as an adult. Some species are myrmecophiles, living near or even inside ant nests.
Ooh, here’s another Braconid Wasp (family Braconidae).
A tiny Jumping Spider glitters behind a ray petal of Grindelia. It is a Buttonhook Leafbeetle Jumping Spider, Sassacus vitis (family Salticidae).
Jumping spiders (family Salticidae) are free-roaming hunting spiders. They do not weave a web to catch prey. They stalk, then pounce on their prey. Just before jumping, the spider fastens a safety line to the substrate. It can leap 10-20 times their body length to capture prey. Their movement is achieved by rapid changes in hydraulic pressure of the blood. Muscular contractions force fluids into the hind legs, which cause them to extend extremely quickly. Jumping spiders are visual hunters. Their excellent vision has among the highest acuities in invertebrates. Since all their 8 eyes are fixed in place and cannot pivot independently from the body like human eyes can, jumping spiders must turn to face whatever they want to see well. This includes moving their cephalothorax up and down, an endearing behavior.
As the spider turns around, its iridescent body appears a darker shade.
It is often difficult to tell whether a particular spider is an adult or an immature, judging by size alone. In the jumping spiders in the genus Sassacus, the adults are only about 3-5 mm. The genus name Sassacus was the last chief of the Pequot Indians, a Native American tribe of the Connecticut Valley that was vanquished in a war with English settlers in 1637. The iridescent color and very compact appearance of these spiders leads scientists to suspect that they are mimics of certain leaf beetles in the family Chrysomelidae. Many Chrysomelids don’t taste good, as they feed on poisonous plants and sequester those plant toxins for their own defense. They advertise their distastefulness to predators with bold black and white, yellow, orange, or red color patterns, or with brilliant metallic colors. One of the defining characteristics of the genus is the very short legs. The fourth pair of legs is still the thickest, with one or two pairs of spines, used in tackling prey. Like most jumping spiders, Sassacus engages in visual courtship displays. The twitching abdomen also produces an auditory stimulus as the male waves his front legs to garner the female’s attention.
Sassacus vitis is native to North America, with a range spanning from Canada to Panama. It is a small jumping spider with iridescent gold abdomen and white ring around the anterior surface of abdomen. Body is covered with golden scales. Males are 3.5 mm long, females 4.5 mm. The name vitis is Latin for “grapevine”. The spider is commonly found on shrubs and vines and in fields. Best known as a common resident of vineyards.
A male Summer Longhorn Bee, Melissodes sp. (family Apidae) has landed to take nectar on a Grindelia flowerhead.
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.
Her head covered with sticky pollen, a female Summer Longhorn Bee, Melissodes sp. (family Apidae) is foraging on a Grindelia flowerhead. She is easily recognizable from the prolific scopae on her hind legs.
A small bee with black-and-white banded abdomen is foraging on a Grindelia flowerhead. I thought it was a Tripartite Sweat Bee, until I saw its large, mottled gray-blue eyes.
As the bee hurries off, I manage to get a glimpse of its abdomen. It is cylindrical, elongated with a tip that curls downward. Ah, it must be the Mason Bee, Ashmeadiella sp.(Megachilidae).
Native to North and Central America, Ashmeadiella is a diverse genus of solitary mason/leafcutter bees in the family Megachilidae, most common in western desert and semi-arid environments. The bees are small, ranging from 3.5 to 9.5 mm in length with robust builds, non-metallic, usually black heads and bodies, and abdomens banded with pale hairs. Males are characterized by four distinct prongs or teeth at the tip of the abdomen. The bees nest in pre-existing cavities like hollow plant stems, abandoned beetle burrows in dead wood, soil, or spaces under rocks. Females divide linear nest tunnels into individual brood cells using chewed-up leaf pulp mixed with resin, sap, gum, or nectar. Many species visit a wide array of wildflowers, while others are floral specialists tied to specific plants.
I marvel that this tiny bee is able to forage on the Fennel flowers buffeted by the wind. It is a Metallic Sweat Bee, Lasioglossum (Dialictus) sp. (family Halictidae).
Lasioglossum species are found worldwide, and they constitute the largest bee genus. The subgenus Dialictus are the most likely to be seen in the U.S., with over 300 species of these tiny metallic bees. The majority of Lasioglossum are generalists. Because they are so abundant throughout the flowering season, the bees are often important pollinators. Their sheer numbers are enough to achieve excellent pollination of many wild flowers, especially of plants in the Asteraceae, which have shallow floral tubes that are easily accessed by these minute bees.
Lasioglossum exhibit a range of social behaviors; the genus includes solitary, communal, semi social, primitively eusocial, and even parasitic species. Almost all Lasioglossum in the U.S. nest in the ground. Generally these nests are built in the spring by fertilized females (called foundresses) that spent the winter in hibernation. In social species, the foundresses behave much like the queen bumble bees – they lay the first batch of eggs that develop into the first generation of female workers. The nest grows with each additional generation of bees. Later broods may consist of both males and females. They mate, and at the end of the season the fertilized females hibernate til the following spring, repeating the life cycle of the colony.
When I first saw the pair of converging white lines on this Lady Beetle’s pronotum, I automatically assumed that it was a Convergent Lady Beetle, Hippodamia convergens (family Coccinellidae). Reviewing the picture at home, I realize that something doesn’t quite add up. iNaturalist has helped identify the beetle as the American Five-spotted Lady Beetle, Hippodamia quinquesignata. Looking through the photos on iNaturalist, I am baffled by the overwhelming variations in coloration and patterns in the species. Apparently, positive identification between the closely related Hippodamia species often requires microscopic examination of the male genitalia. I am happy to leave that to the taxonomists!
The American Five-spotted Lady Beetle, Hippodamia quinquesignata (family coccinellidae) is found across North America, including western regions and parts of Alaska. The species inhabits meadows, grasslands, and croplands. The beetles are a generalist predator that feeds primarily on aphids and other small, soft-bodied insects.
A Small Carpenter Bee, Ceratina sp. (family Apidaea) is collecting pollen from the stamens of an Armenian Blackberry, Rubus armeniacus.
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.
A female Forked Globetail, Sphaerophoria sulphuripes (family Syrphidae) has landed on a Grindelia leaf.
She curls her abdomen forward with a fully extended tip as if to lay an egg.
The Forked Globetail, Sphaerophoria sulphuripes (family Syrphidae) is a hover fly native to western North America. Adults visit flowers for nectar and pollen. Larvae feed on aphids and other soft-bodied insects. There is marked sexual dimorphism in the species – the males have a slender abdomen with a reddish, swollen tip.
