February 19, 2018
 
 
 Sierra Gooseberries Blooming With Pollinators
By Nancy Gilbert, Redbud CNPS Horticulture Chair
 
Even though frost and snow may still come our way in the next couple of months, we have had a very warm and dry period in late January and the first half of February, with the result that many native plants are blooming early this year.
 
It is warm enough and there are sufficient blooms on our locally native plants, such as Whiteleaf Manzanita and Sierra Gooseberry, that the early emerging native pollinators are already flying and busily gathering nectar and pollen. So, I have been out and about with my camera stalking the native pollinators to see who is pollinating what.
 
It is warm enough and there are sufficient blooms on our locally native plants, such as Whiteleaf Manzanita and Sierra Gooseberry, that the early emerging native pollinators are already flying and busily gathering nectar and pollen. So, I have been out and about with my camera stalking the native pollinators to see who is pollinating what.
 
I am intrigued by our native pollinators, especially bees, and have been photographing and studying them for the past few years, but I still have quite a lot to learn, as identifying many of them can be tricky. That said, with the aid of some excellent books and good close-up photos, I think I am becoming much more familiar with these incredibly diverse and important insects.
 
I have been especially interested in observing the pollinator activity on the Sierra Gooseberry, Ribes roezlii, which is in peak bloom right now.
 
The flowers of the Sierra Gooseberry are quite enchanting, with their red and pink-white blooms dangling downwards like Christmas tree lights along the prickly stems.  They are best appreciated up close, as they are small and delicate with a complex structure that creates a challenge for large-sized insect pollinators. 
 
While I have seen the occasional visiting Hover Fly or Black Tail Bumblebee, by far the most frequent pollinator visiting these gooseberry flowers are the Metallic Sweat Bees, genus ioglossum. At first you might think they are a small, shiny black fly, but closer inspection reveals their true identify as a native Sweat Bee.
 
The females gather and transport the plant pollen with scopae (specialized, sticky hairs) located on their outer hind legs inward towards the sides of the thorax, giving them the appearance of wearing pantaloons. These small and agile native bees are just the ticket for accessing and pollinating those little upside-down flowers. Like aerial acrobats, they fly underneath the reflexed, outer sepals, grasp the smaller, pink-white, inward rolled petals and then hang under the styles and anthers, while sipping the nectar and gathering the pollen.
 
The males are somewhat smaller than the females and have no scopae for collecting pollen. The bees effectively fertilize the flower in the process of feeding and gathering pollen.
 
Metallic Sweat Bees fly in late winter and early spring when the sun is shining and it is warm, and the females build nests for rearing their young in the ground. So, on a sunny day in the upcoming weeks, sit down quietly near an early-flowering gooseberry or currant and watch to see if you can spot these industrious little native pollinators flitting among the flowers.
 


     
Male Sweat Bee  
     
Sierra Gooseberry with Male Sweat Bee. Male bees are smaller than females, have a narrower abdomen and don’t have scopae for gathering pollen. They feed only on nectar.
Female Metallic Sweat Bee arriving at Sierra Gooseberry flower. She has clearly visible pollen sacs, which is where the scopa on legs and inner abdomen collect pollen to be transported to her nest.
 
     
Pollen Laden Female Sweat Bee Sunning Female Sweat Bee  
     
Female flying among Sierra Gooseberry flowers. Note her pollen-laden scopae on hind legs clearly visible.
Female Sweat Bee sunning on leaf of Sierra Gooseberry. She is moving her tongue in and out, possibly to move nectar to her crop or to evaporate the nectar? More research needed on this behavior.
 
     
Acrobatic Female Sweat Bee    
     
Female Sweat Bee performing acrobatics to reach the nectar and pollen of the gooseberry flowers.