Pollinator Post 5/20/26 (2)
The Armenian or Himalayan Blackberry, Rubus armeniacus growing along the Shoreline trail at Bay Farm is blooming in profusion. Since few other plants are in bloom and offering floral resources around here, the blackberry is the intense focus of many insects.
To tell the native California Blackberry (Rubus ursinus) apart from the invasive Armenian/Himalayan Blackberry (Rubus armeniacus), look at the canes, prickles, and leaf structure. Native canes are trailing, round, and covered in soft, hair-like bristles, Armenian canes grow upright/arch into thickets, are angled, and have sharp. rose-like thorns. Compared to the native blackberry, the flowers of R. armeniacus are larger, with distinctly round, white to pale pink petals that are curved, forming a bowl-shaped corolla. I have also learned an easy way to distinguish the two species at the fruiting stage – on the developing fruits of the Armenian Blackberry, one usually sees many dried stamens surrounding the green berry. This is because this species has bisexual or perfect flowers with both sexes on the same flower. In contrast, the native California Blackberry is dioecious, with male and female flowers borne on separate plants. When the female flowers of this species are developing fruits, one never sees spent stamens (male parts) surrounding the berries.
A Gray Buckeye butterfly lands on an Armenian Blackberry flower to take nectar.
The butterfly that I used to identify as Common Buckeye Butterfly, Junonia coenia (family Nymphalidae) is now known as Gray Buckeye, Junonia grisea, formerly known as a subspecies of J. coenia. As of 2018, the entire Buckeye population west of the Rockies is now considered a separate species, the Gray Buckeye, J. grisea, due to some subtle morphological and genetic differences.
Named for its conspicuous target-shaped eyespots, the mainly brown Buckeye butterfly is readily identifiable. There is also the prominent orange “quotation marks” on the leading edge of the forewings of the butterfly. The butterfly favors open, sunny areas with low vegetation and some bare ground. Males perch during the day on low plants or bare ground to watch for females, flying periodically to patrol or to chase other flying insects. Females lay eggs singly on leaf buds or on upper side of host plant leaves. Caterpillars feed on a variety of plants within the Plantago genus. Female Buckeye butterflies identify their host plants by using specialized sensors on their feet to detect bitter iridoid glycosides, chemical compounds naturally found in Plantago species. The caterpillars eat the leaves and sequester the iridoid glycosides, rendering themselves unpalatable to predators. Here at Shoreline Park, the butterflies find an abundant larval food plant in the Buck’s-horn Plantain, Plantago coronopus growing in the salty, sandy soil.
The flowers of the Armenian Blackberry are abuzz with insects of all kinds. Here, a Small Carpenter Bee, Ceratina sp. (family Apidae) is sharing floral resources with a Spotted Cucumber Beetle, Diabrotica undecimpunctata (family Chrysomelidae). The beetle is the one with the long antennae.
A small Carpenter Bee, Ceratina sp. (family Apidae) is foraging on an Armenian Blackberry flower.
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. Dead or broken blackberry canes are among Ceratina’s absolute favorite nesting spots.
The Small Carpenter Bees, Ceratina sp. are out in force today, foraging on the blackberry flowers. It is likely that these females have excavated nest cells in the old or broken blackberry canes. Room and board on the same plant – life couldn’t be any sweeter!
Look, a Scarab beetle on a senescing Armenian Blackberry flower (family Rosaceae)! iNaturalist has helped identify it as a Grapevine Hoplia, Hoplia callipyge (family Scarabaeidae).
Ventral view of the stocky beetle as it climbs up the stamens of the flower.
Hoplia beetles are small (1/4 inch long), and often brownish, sometimes with a slightly lighter, two-toned appearance. They swarm and feed on light-colored roses and other flowers in early spring, leaving ragged holes. They do not feed on leaves. The beetles appear from the soil from March to May in California, with one generation per year.
Hoplia beetles (tribe Hopliini) are nicknamed “monkey beetles” primarily for their hind legs which are noticeable larger and longer than their other legs, used for gripping flower petals and for locomotion. The beetles often engage in acrobatic, monkey-like behavior, such as hanging by their hind feet and sometimes performing somersaults while navigating flowers. They are active pollinators and flower-feeders known for agile movements while navigating thickets of pollen.
Rear view of the same Grapevine Hoplia.
The Grapevine Hoplia, Hoplia callipyge (family Scarabaeidae) is found in the western United States, in British Columbia in Canada, and in Baja California in Mexico. Adults are about 5.8 to 10.5 mm long. Active in March through May, they are often found on the petals of light-colored roses. (Blackberry is in the rose family.) However, they will also feed on other flowers and the young leaves and fruit of certain plants, including grapevines and ornamentals. Larvae hatch from white eggs in soil and feed on roots and decaying plants. Adults emerge in spring.
A small wasp is perched on the base of the stamens of an Armenian Blackberry flower. Is it trying to take nectar, or is it searching for potential host? iNaturalist has helped identify the wasp as Cotesia sp. (family Braconidae).Cotesia is a genus of parasitoid wasps in the family Braconidae. Some species parasitize caterpillars of species considered pests, and are used as biocontrol agents. A well-known species, Cotesia glomerata feed on the cabbage white and other white butterfly caterpillars. Female wasps seek out the host caterpillars and inject eggs into them. The eggs hatch and the wasp larvae feed on the caterpillars from the inside out. When mature they emerge from the host caterpillar and immediately spin a cocoon around themselves. Adding insult to injury, the host caterpillar is also chemically manipulated into staying around to protect the wasp pupae. It’s one of the most gruesome and chilling story of parasitism in nature.
A Honey Bee, Apis mellifera (family Apidae) is foraging on a flower of Armenian Blackberry flower. She is probably seeking nectar, not pollen, since there are only spent stamens on the flower.
A Yellow-faced Bumble Bee, subgenus Pyrobombus (genus Bombus, family Apidae) is foraging on a blackberry flower.
As the bee moves to another blackberry flower, I begin to notice the huge load of inconspicuous putty-colored pollen in her pollen baskets.
The pollen collecting apparatus in Apidae bees, which include honey bees and bumble bees, is commonly called a “pollen basket” or corbicula. This region is located on the tibia of the hind legs and consists of hairs surrounding a concave region. After the bee visits a flower, she begins to groom herself and brushes the pollen down toward her hind legs and packs the pollen into her pollen basket. A little nectar mixed with the pollen keeps it all together like putty, and the stiff hairs surrounding the pollen basket hold it in place. Remarkably bees are able to fly while carrying up to a third of their body weight in pollen.
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An Acmon Blue butterfly is taking nectar on a cluster of Wild Mustard flowers.
Acmon Blue, Icaricia acmon (family Lycaenidae) is a North American butterfly, found mostly in California. It is a small butterfly, with a wingspan of 0.75 to 1.125 in. It can be seen from March to October, with peak numbers in July. Adults feed on nectar while caterpillars feed on a variety of plant species, including buckwheats, deer weed, lupines, trefoils, and milkvetches. Like many Lycaenid butterflies, Acmon Blue shares a mutualistic relationship with ants. The ants protect the caterpillars from predators in exchange for the sweet “honeydew” the caterpillars secrete from a nectary gland. The larvae are often protected and kept in the ant nest when not feeding.
A Small Carpenter Bee, Ceratina sp. (family Apidae) is foraging on a flower of Wild Mustard.
A Lygus Bug, Lygus sp. (family Miridae) is perched on cluster of Wild Mustard flowers.
Lygus is a genus of plant-feeding insects belonging to the true bug family Miridae. They are small, oval-shaped, and somewhat flattened bugs with a characteristic triangle-shaped area (scutellum) between their wings. Adults are typically brown, yellowish, or greenish. Because they are highly polyphagous (feeding on a wide variety of plants), they can impact over 300 different cultivated crops, including strawberries, tomatoes, cotton, alfalfa, apples, and various beans. Their feeding habits, using piercing-sucking mouthparts, often cause blossoms to drop, irregular scarring or dimpling on fruits, and deformed or stunted shoot terminals.
Whoa, that’s a Thick-headed Fly (family Conopidae) on the Wild Mustard flowers! The fly is a wasp mimic, but its reddish-brown coloration and antennae are quite distinctive.
The small and little-known family of Conopidae, commonly called the Thick-headed Flies, are distributed worldwide. Remarkable mimics of wasps and bees, the flies are frequently found at flowers, feeding on nectar with their long probosces. The larvae of all Conopids are internal parasitoids, mostly of aculeate (stinging) Hymenoptera (wasps, bees). Adult females aggressively intercept their hosts in flight to deposit eggs. Vulnerable foraging bees are likely the most susceptible to parasitism by Conopids. The female’s abdomen is modified to form what amounts to a “can opener” to pry open the segments of the host abdomen as the egg is inserted. The fly larva feeds on the host from the inside out. The bee host continues to live, and is able to fly throughout the duration of the larval developmental period. The vast majority of parasitized bumble bees bury themselves by burrowing into the ground right before they die. This behavior does not matter to the bees – they are doomed. But it is critical for the flies – if the host dies underground, the fly is sheltered from the elements, predators and parasites. Pupation occurs in the abdomen of the now deceased bee host. The adult fly typically emerges after overwintering in the abdominal puparium of the bee.
The life spans of parasitized bumble bees are not significantly shortened, though as the parasitoid grows, the bee can’t carry home as much nectar. Bumble bees will chill, literally, to put off the inevitable, seeking cooler spots, even sleeping outside at night to slow the growth within them. If many of the workers in a colony are infested, future queens may be smaller in size and may not have enough energy to get through the winter.
If it’s any consolation, this individual appears to be a male. Females have an easily noticeable prominent bump under the fifth sternite of the abdomen; in addition, their terminal abdominal segment forms a plate-like hook used to pry open bee and wasp segments mid-flight to deposit eggs.
Horrifying as their parasitizing modus operandi is, I am comforted by the thought that the presence of these flies is an indication that the local bee and wasp populations are robust enough to support them.
A small insect is resting on a leaf of a small Curly Dock growing on the lawn. Its head appears to be entirely made up of its eyes. iNaturalist has helped identify it as a Sugarcane Soldier Fly, Inopus rubriceps (family Stratiomyidae). It is a male of the sexually dimorphic species.
The Sugarcane Soldier Fly, Inopus rubriceps (family Stratiomyidae) is native to eastern Australia where it infests such crops as corn, pastures, and sugarcane. The fly was accidentally introduced into California over 50 years ago. It is now infesting lawns in San Francisco and other Bay Area counties. Damage to turf and other members of the grass family results from withdrawal of sap from roots of host plants by the larvae and possibly, injection of a toxin into the plant.
In California adults occur in large numbers from late September to early November each year. Eggs are deposited in crevices in the soil. The adults are sexually dimorphic. Females have tiny red heads with eyes set far apart. The smaller males have large eyes that occupy the whole surface of the head. Adults are non-feeding or drink only liquids such as flower nectar and honeydew. They are strictly focused on mating and laying eggs during their short, few-day lifespan.