Pollinator Post 6/15/23 (1)
It’s been a while since I last explored the stretch of Skyline Trail from the Steam Train entrance. I decide to make a visit this afternoon.
A Soft-bodied Plant Beetle, Dascillus davidsoni (family Dasciilidae) is watching me from a Coyote Brush. The species is found in North America.
Dascillidae is a family of beetles found worldwide. Adults are 4.5-25 mm long with elongate body that is somewhat convex in cross-section. They are covered in dense gray/brown hairs. The adults can be found on grass during the springtime. The larvae occur in moist soil or under rocks. The larvae are thought to feed on roots or decaying plant matter.
There are Snakeflies everywhere on the Coyote Brush, Baccharis pilularis. I have never seen so many Snakeflies in one place – what’s happening? Is this a mating aggregation?
Snakeflies are a group of predatory insects comprising the order Raphidioptera. They are a relict group, having reached their apex of diversity during the Cretaceous before undergoing substantial decline. Adult Snakefly has a notably elongated thorax which, together with the mobile head, gives the group their common name of snakily. The body is long and slender and the two pairs of long membranous wings are prominently veined. The head is long and flattened and heavily sclerotized. The mouthparts are strong and relatively unspecialized, being modified for biting. The large compound eyes are at the sides of the head. Females have a large and sturdy ovipositor which is used to deposit eggs into crevices or under bark. Snakeflies are holometabolous insects with four-stage life cycle consisting of eggs, larvae, pupae and adults. Both adults and larvae are predators of soft-bodied arthropods such as aphids and mites.
The Snakefly has been identified as belonging to the genus Agulla. Seen here is a female, with a long ovipositor. Seen dorsally, the head has a “kite-like” shape; ocelli are present (though not discernable here). The genus is found in western North America.
This female Snakefly, Agulla sp. (family Raphidiidae) is perched on a flower of Bee Plant.
The California Bee Plant, Scrophularia californica is blooming well along this partially shady stretch of Skyline Trail. Many of these small bees are frequent visitors to the small flowers. About the same size as the flower, the bee does not enter the corolla, but hangs on the entrance to sip nectar or collect pollen. These are probably Mining Bees, Andrena sp. (family Andrenidae)
A very small worker Yellow-faced Bumble Bee, Bombus vosnesenskii visits a Bee Plant flower for nectar. Surprisingly, bumble bees are some of the most frequent visitors. I am always amazed at how the small flowers and their stalks can withstand the weight of these large bees, even the occasional queens. The flowers never droop and the stalks never bend under the weight of these hefty bees. I think the Bee Plant flowers are actually meant to be pollinated by large insects.
A Honey Bee, Apis mellifera comes along and do the same.
A male Diamond Spottail, Fazia micrura (family Syrphidae) lands on a California Bee Plant flower. From the fresh, protruding stigma, I gather that the flower is in its female phase and not yet producing pollen. Bee Plant flowers are protogynous, meaning the female parts mature before the male parts.
The hover fly reaches forward to sip nectar. If it has been visiting a male flower previously, some of the pollen on its body could be deposited on the stigma of this flower.
There, the hover fly is retracting its proboscis. We can see that there are no anthers at the front of the corolla (as the male structures have yet to be presented).
Temporal separation of the sexes, or dichogamy, is a plant’s strategy for avoiding self-pollination.
Some movements on the top leaves of a Coyote Brush, Baccharis pilularis catches my attention. A small Fruit Fly (family Tephritidae) is performing a wing display, running around and moving its picture wings alternately in figure-8 rotation. The fly is female, as evidenced by the oviscape on the tip of her abdomen. 
Tephritids are small to medium-sized flies that are often colorful, and usually with picture wings. The larvae of almost all Tephritidae are phytophagous. Females deposit eggs in living, healthy plant tissues using their telescopic ovipositors, sometimes forming galls. Here the larvae find their food upon emerging. The larvae develop in leaves, stems, flowers, seeds, fruits, and roots of the host plant, depending on the species. Adults are often found on the host plant and feeding on pollen, nectar, rotting plant debris, or honeydew. Tephritid flies are of major economic importance as they can cause damage to fruit and other plant crops. On the other hand, some Tephritids are used as agents of biological control of noxious weeds.
Many species of Tephritidae perform an elaborate courtship display using their picture wings.
Female Tephritidae can often be distinguished easily from the males by the possession of a conspicuous oviscape at the tip of their abdomen. The oviscape is the basal part of the ovipositor of some insects, typically the non-retractile sclerotized sheath that remains exposed when the telescopic ovipositor is withdrawn and not in action.
Why is the Fruit Fly doing this elaborate wing display? Who is the intended audience? I look around but don’t see any other fruit fly in the vicinity.