Pollinator Post 8/11/26 (2)
A male Fine Striped Sweat Bee, Agapostemon subtilior (family Halictidae) is taking nectar on a flowerhead of Oregon Gumweed, Grindelia stricta.
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.
The Fine Striped Sweat Bee, Agapostemon subtilior is a small, widespread species found across North America. They are active from late spring to fall, with all-green females measuring roughly 11 mm, and males (slightly smaller) displaying a black-and-yellow striped abdomen. Like other Agapostemon bees, they are solitary ground-nesters, and are polylectic, foraging from a wide variety of flowers.
On closer examination, a shiny spot on a Grindelia ray petal turns out to be 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.
Not all shiny spots on the Grindelia are Bronze Leaf Beetles. Often they turn out to be Buttonhook Leafbeetle Jumping Spiders, 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.
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.
Jumping spiders have a unique eye arrangement consisting of eight eyes in four pairs. The most prominent pair are the two large, forward-facing anterior median eyes (AMEs), which provide sharp, detailed vision and depth perception. The other three pairs are smaller secondary eyes: two anterior lateral eyes (ALEs), two posterior median eyes (PMEs), and two posterior lateral eyes (PLEs). These secondary eyes offer a wider field of view and help with detecting movement.
An unfamiliar bee is foraging on a Grindelia flowerhead. I try to take as many pictures of it as possible, hoping that I could get help identifying it.
The compact, stocky body, large head and eyes remind me of the Short Sun-digger Bee, Anthophroa curta commonly seen around here, but the coloring is distinct. Is this another species in the subgenus Micranthophora, the “mini digger bees”?
Two bee experts from iNaturalist responded promptly to my photos to confirm that indeed the bee is a member of the subgenus Micranthophora. What would I do without this wonderful community of nature lovers who are so generous with their knowledge and expertise!
Micranthophora is a subgenus of small Digger Bees belonging to the genus Anthophora (family Apidae). Found primarily in the New World (from the southwestern United States down to Honduras), these bees feature distinct yellow facial markings in females and are noticeably smaller than other regional Anthophora species. They are often found thriving in dry, xeric, or desert-like environments.
Anthophora is a large genus of solitary, ground-nesting bees in the family Apidae, commonly known as Digger Bees. They are famous for their fast, darting flight and status as elite generalist pollinators. Their long tongues enable them to effectively pollinate deep, tubular flowers that short-tongued bees cannot reach.
A Gray Hairstreak lands upside down on a young Oregon Gumweed, Grindelia stricta. It is a very fresh individual, with not a scale out of place.
Why the name “hairstreak”? These small butterflies have a slim, hair-like tail on the lower corner of each hindwing. Gray Hairstreak also has colorful false eyespots near the base of each tail. The eyespots and antenna-like tails are believed to fool predators into mistaking its tail for its head. Hairstreaks even add a behavioral component – a nectaring hairstreak often rubs its wings up and down, simulating the movement of twitchy antennae. This may fool birds, lizards, and spiders into attacking the wrong end, sparing the life of the butterfly.
Female Gray Hairstreaks lay eggs singly on the flowers, flower buds, young fruits and nearby leaves of a host plant. Host plants include a wide variety of plants, notably from the pea (Fabaceae) and mallow (Malvaceae) families. The caterpillars are greenish at the start, but older individuals range in color from gray to pink. As in many species of Lycaenidae, Gray Hairstreak larvae are myrmecophiles (ant-lovers) – often tended by ants. Ants harvest a sweet liquid from the caterpillar’s dorsal nectary organ (“honey gland”) and in exchange may protect them from predators. Larvae of many Lycaenidae species also communicate with ants via ant-like sounds (clicks and hums) or by sending vibrations through the substrate.