Pollinator Post 5/24/26 (2)
A Metallic Sweat Bee, Lasioglossum (Dialictus) sp. (family Halictidae) is foraging on the small, clustered flowers of California Buckwheat, Eriogonum fasciculatum. These bees have short tongues and are unable to access nectar from deep, tubular flowers. Instead, they rely on smaller, shallow flowers where the nectar and pollen are easy to reach. Tongue length dictates a bee’s foraging niche. While long-tongued bees (like bumble bees, carpenter bees, or digger bees) are specifically adapted to exploit deep flowers, short-tongue bees (like sweat bees, miner bees, and cellophane bees) are specifically adapted to flatter blossoms.
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.
A Thick-legged Hover Fly, Syritta pipiens (family Syrphidae) is foraging on a flower of California Buckwheat.
Syritta pipiens originates from Europe and is currently distributed across Eurasia and North America. They are fast and nimble fliers. The fly has an elongate body about 6.5 – 9 mm long, and has distinctly enlarged hind femora which gives it its common name. The species flies at a very low height, rarely more than 1 m above the ground. Adults visit flowers – males primarily to feed on nectar, and females to feed on protein-rich pollen to produce eggs. The species is found wherever there are flowers. It is also anthropophilic, occurring in farmland, suburban gardens, and urban parks. Larvae are found in wetlands that are close to bodies of freshwater such as lakes, ponds, rivers, ditches. Larvae feed on decaying organic matter such as garden compost and manure. Males often track females in flight, ending with a sharp dart towards them after they have settled, aiming to attempt forced copulation.
A Yellow-faced Bumble Bee, subgenus Pyrobombus (genus Bombus, family Apidae) is foraging on an unidentified flowerhead with tightly clustered flowers and long stamens, reminiscent of thistle.
A Monarch butterfly, Danaus plexippus (family Nymphalidae) has landed to take nectar from an inflorescence of Showy Milkweed flowers, Asclepias speciosa.
While they can take nectar from a wide variety of flowers, Monarch females will only lay their eggs on milkweed because it is the only food source their caterpillars can digest. The plant also provides crucial chemical defenses; the larvae ingest and sequester milkweed toxins (cardiac glycosides), making them unpalatable and poisonous to predators throughout their life cycle. Female monarchs have adapted specialized receptors on their legs and antennae to taste and detect the specific chemical signatures of milkweed, ensuring they never misplace their eggs. The adults utilize aposematism – the use of bright, contrasting colors to warn predators of toxicity. Their iconic orange and black wings signal that they are unpalatable and potentially harmful, allowing them to survive encounters with birds and other animals.
A Large Milkweed Bug, Oncopeltus fasciatus (family Lygaeidae) is exploring a leaf of Showy Milkweed.
Milkweed Bugs are Seed Bugs (family Lygaeidae) in the insect order of “true bugs”, Hemiptera. The bold red-and-black coloration of the bug serves as aposematic warning to potential predators of its distastefulness and toxicity. Like the Monarch butterflies, Oncopeltus sequesters the toxic compounds of milkweeds. The bugs undergo incomplete metamorphosis, with five instars before reaching adulthood. The nymphs and adults all feed on milkweed using their piercing-sucking mouthparts. Adults are capable of penetrating the seed pod with their proboscis and injecting digestive juices. All stages of development can be found on the plants in mid to late summer. Adults live for about one month. The insect overwinters as an adult.
There are several scattered patches of Showy Milkweed, Asclepias speciosa growing in the garden, but I can’t find any Monarch eggs or caterpillars on them. Instead I find this small colony of Oleander Aphids, Aphis nerii (family Aphididae) on the back of a young leaf. Note the winged aphid and the white exuvia (shed exoskeletons). Female aphids are viviparous and parthenogenetic, meaning that they give birth to live young instead of laying eggs, and that the progeny are produced by the adult female without mating. The nymphs feed gregariously on the plant terminal in a colony that can become quite large. Nymphs progress through five nymphal instars without a pupal stage. Normally wingless adults are produced but alate adults occur under conditions of overcrowding and when plants are senescing, allowing the aphids to migrate to new host plants. The parthenogenetic mode of reproduction, high fecundity, and short generation time allow large colonies of Oleander Aphids to build quickly on infested plants.
The Oleander Aphid ingests sap from the phloem of its host plant. The damage caused by aphid colonies is mainly aesthetic due to the large amounts of sticky honeydew produced by the aphids and the resulting black sooty mold that grows on the honeydew. The terminal growths of host plants may be deformed, resulting in stunted growth in heavy infestation.
Oleander Aphids sequester cardiac glycosides, a toxin from their host plants. They also fortify their cornicle secretions with these bitter, poisonous chemicals. Their bright aposematic (warning) coloration and possession of toxins protect them from predation by certain species of birds and spiders. Aphid populations are usually kept under control by natural biological agents such as parasitoid wasps, and predators such as Syrphid larvae, Lacewing larvae, and Lady Beetles.
A young Jumping Spider, Phidippus sp. (family Salticidae) is hunting on a senescing inflorescence of Sulfur Buckwheat, Eriogonum umbellatum.
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, a behavior humans find endearing.
Look who else is on the Sulfur Buckwheat – a foraging Metallic Sweat Bee, Lasioglossum (Dialictus) sp. (family Halictidae).
Carrying a large load of yellow pollen in her pollen baskets, a Fog-belt Bumble Bee, Bombus caliginosus (family Apidae) is foraging on the flowers of Phacelia.
Bombus caliginosus, widely known as the Obscure Bumble Bee or Fog-belt Bumble Bee, is a species native to the West Coast of the United States. As the name suggests, this bee thrives in cool, moist, and coastal environments stretching from Washington through Oregon down to Southern California. The bee is notoriously difficult to distinguish from the much more common Yellow-faced Bumble Bee, Bombus vosnesenskii. Both have a distinct yellow face. B. caliginosus generally has longer, more uneven hair and features longer cheeks. Crucially, it often has noticeably yellow hairs on the underside of its abdomen. The Fog-belt Bumble Bee also appears slightly more shaggy or unkempt, whereas the Yellow-faced Bumble Bee looks well-groomed with more even fur. Both species are pollen generalist that visit a wide variety of flowers.
A tiny black bee is collecting pollen from the stamens on a flower of California Phacelia, Phacelia californica.
Do you see the yellow patches on the bee’s legs and face? The bee is a Masked Bee, Hylaeus sp. (family Colletidae)!
Now the bee is reaching for the nectar at the base of the flower. These short-tongued bees are small enough to enter the flower to access nectar.
Hylaeus (family Colletidae) are shiny, slender, hairless, and superficially wasp-like bees. They are small, 5 to 7 mm long, usually black with bright yellow or white markings on their face and legs. These markings are more pronounced on the males. Hylaeus do not carry pollen and nectar externally, they instead store their food in the crop and regurgitate it upon returning to their nests. They are primarily generalist foragers. Hylaeus are short-tongued, but their small body size enables them to access deep flowers. Hylaeus nest in stems and twigs, lining their brood cells with self-secreted cellophane-like material. They lack strong mandibles and other adaptations for digging, using instead pre-existing cavities made by other insects.
In case you wonder – yes, pink Yarrow is completely natural. While the most common wild Achillea millefolium is white, natural variations with light pink or rose-colored flowers occur in the wild across North America and Europe.
Do you see the little Inchworm posing in its classic inverted U-shaped stance on one of the Yarrow flowerheads? It is a caterpillar of the Pug Moth, Eupithecia sp. (family Geometridae).
Inchworms are also called loopers and measuring worms. The 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. The “looping” locomotion is mandated by the absence of prolegs in the middle section of the caterpillar’s body.
Eupithecia is the largest genus of moths of the family Geometridae. Occurring worldwide except for Australasia, species in the genus are commonly known as pugs. The caterpillars move in a looping manner and are commonly called inchworms. 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. Many are commonly found on Asteraceae flowers.
A small, elongate hover fly lands on a cluster of Yarrow flowerheads. Ah, I think I know who it is from the bowed hind legs and the abdominal pattern.
It is a Thick-legged Hover Fly, Syritta pipiens (family Syrphidae). Note the enlarged femur on the hind leg which gives the fly its common name.
Syritta pipiens originates from Europe and is currently distributed across Eurasia and North America. They are fast and nimble fliers. The fly is about 6.5 – 9 mm long. The species flies at a very low height, rarely more than 1 m above the ground. Adults visit flowers – males primarily to feed on nectar, and females to feed on protein-rich pollen to produce eggs. The species is found wherever there are flowers. It is also anthropophilic, occurring in farmland, suburban gardens, and urban parks. Larvae are found in wetlands that are close to bodies of freshwater such as lakes, ponds, rivers, ditches. Larvae feed on decaying organic matter such as garden compost and manure. Males often track females in flight, ending with a sharp dart towards them after they have settled, aiming to attempt forced copulation.
A European Paper Wasp, Polistes dominula (family Vespidae) is hunting on an inflorescence of Fern-leaf Yarrow, Achillea filipendulina.
European Paper Wasps are yellow and black, and they sting, so they are frequently mistaken for yellowjackets (Vespula spp.). Paper wasps have slender bodies with a thin waist, and they have orange-tipped antennae. Yellowjackets have shorter, thicker bodies, and they have black antennae. Paper wasps dangle their long legs when they fly, while the yellowjackets tuck their legs under their bodies when they fly. Paper wasp nests resemble an open honeycomb or upside-down umbrella. They often build their nests on man-made structures such as eaves or lawn furniture. Yellowjacket nests are covered with a surrounding envelope of paper; the nests have a single opening that is often hard to see because they are underground.
Native to Europe, the European Paper Wasp, Polistes dominula (family Vespidae) is a social insect that produces an annual colony in a paper nest. Individual colonies are established anew each spring. The overwintering stage are mated females (queens). The overwintered queens emerge from sheltered spots in spring and search out sites to establish a new colony. Nests are constructed of paper, produced from chewed wood fibers of weathered fences, porch decks and other similar sources. Larvae are fed crushed insects, usually caterpillars. As the population increases, the original queen increasingly remains in the nest as new workers take over colony activities. A few of the wasps produced later in summer are males and increasing numbers of the females become sexually mature. Mating occurs and the mated females are the surviving overwintering stage. Males and non-reproductive females do not survive winter and the nest is abandoned by late fall. European Paper Wasps will sometimes feed on sweet materials, including honeydew produced by aphids. They may also feed on damaged ripe fruits. Because of their habit of hunting caterpillars, the wasps have become one of the most important natural controls of garden pests.
Vespid wasps (such as yellowjackets, hornets, and paper wasps) have distinct diets for adults and larvae, functioning as both predators and foragers. Adult wasps cannot digest solid food. They use their large mandibles to lap up liquid carbohydrates like plant nectar, tree sap, and honeydew. Larvae require protein for growth. Adult wasps hunt insects (like caterpillars and flies) and chew and condition them into a soft meat pulp, which they feed to the larvae in the nest. In exchange, the larvae secrete a sweet, amino-acid-rich liquid which the adults consume; the larvae essentially serve as the digestive system of the adults. This cyclical exchange of food between adults and larvae is called trophallaxis.
Bouncing manically from one flower to the next, a male Foothill Carpenter Bee, Xylocopa tabaniformis orpifex (family Apidae) stops for a quick sip of nectar from Wild Kopieva, Bulbine frutescens.
The common name “carpenter bees” derives from their nesting behavior; nearly all species burrow into hard plant material such as dead wood or bamboo. These robust bees are often mistaken for bumble bees. The simplest way to tell them apart is that most carpenter bees have a shiny abdomen, whereas bumble bees abdomens are completely covered with dense hair. Males of some species of carpenter bees have a white or yellow face, unlike bumble bees, while females lack the bare corbicula (pollen baskets) of bumble bees; the hind leg is entirely hairy and includes the scopa.
Carpenter Bees are traditionally considered solitary bees, though some species, including our Foothill Carpenter Bee, have simple social nests in which mothers and daughters may cohabit. Carpenter Bees make nests by tunneling into wood, bamboo and similar hard plant materials. They vibrate their bodies as they rasp their mandibles against the wood, each nest having a single entrance which may have many adjacent tunnels. The entrance is often a perfect circular hole measuring about 0.6in. on the underside of a beam, bench, or tree limb. Carpenter Bees do not eat wood; they discard the bits of wood, or reuse the sawdust to build partitions between cells. The tunnel functions as a nursery for brood and storage for the pollen/nectar upon which the brood subsists. Carpenter can be timber pests, and cause substantial damage to buildings.
Carpenter Bees have short mouthparts and are important pollinators on some open-faced or shallow flowers. They also are important pollinators of flowers with various forms of lids, such as Salvia species, and some members of the Fabaceae such as Lupinus. Many Carpenter Bees are known to “rob” nectar by cutting slits on the sides of tubular flowers that they cannot enter. In doing so, the bees can access the nectar directly with their short tongue. This move precludes contact with the reproductive parts of the flower, and results in no pollination.
A female Foothill Carpenter Bee, Xylocopa tabaniformis orpifex (family Apidae) is visiting the same patch of Wild Kopieva. Note that unlike the male, she is entirely black.
After the group has left at the end of our bee walk, Elizabeth and Emil stay behind at the front gate to try to photograph a bee we saw earlier – the native Spotted Woolcarder Bee, Anthidium maculosum (family Megachilidae). Despite his massive inventory of bee images, Emil has yet to add this elusive bee to the collection. His dedication and love of bees is an inspiration for us all.