By Constance Taylor
Eddie Dunbar from the Insect Sciences Museum of California led another fantastic walk for Wild Oakland!
We started at “butterfly alley”, the pollinator corridors at Lakeside Gardens, and came face-to-face with some of the smaller citizens of our fair city.
One of the first insects we noticed were the monarchs flitting around the milkweed. Thanks to forward-thinking folks who work for the city of Oakland, the parks department has begun to plant things in public areas that are especially attractive to our native pollinators.
Milkweed is a major food source for monarch caterpillars- the caterpillars feed on the plant and retain the poison even as adults, making them toxic to predators!
Eddie, who is well-practiced in not harming insects for the sake of observation, carefully plucked one off of a plant to show us how to tell a male monarch from a female:
See those two black dots on the hind wings? It’s a male! The glands release pheromones to attract females.
We saw a host of different bees around the pollinator gardens, including these…
Yellow-faced bumblebee (Bombus vosnesenskii), the largest bumblebee in the Bay Area!
These are offensive spines on the posterior used by the male European Wool Carder Bee to attack challengers to its territory. You can read an interesting article about these bees here.
Black-tailed bumblebee (Bombus melanopygus edwardsii), subspecies of the Red-Tailed bumblebee.
All these bee sightings segued nicely into our arrival at the brand new bee hotel in the gardens…
The bee hotel was built just a few months ago in April 2013 by the Oakland Building Services Department, and volunteers are currently working to fill it with things that our native bees like to live in.
Many native bees in California are solitary, and lay their eggs underground or nest in small holes in dead wood made by longhorn beetles (family Cerambycidae) or other insects- hence the small logs in the bee hotel that have been drilled to mimic that habitat.
“Bees in Oakland are homeless,” said Dunbar. “We usually cut down and remove dead trees in the city, which means that we’re removing important habitat they could live in.”
Another habitat issue is mulching- many native bees lay their eggs by burrowing into the dirt and depositing a single egg into each hole. They can’t do that if there’s mulch blocking their way, so the Lakeside gardens are working towards removing this unnatural duff to create more space for bees to thrive.
You can read a great article from 2008 about native bee habitat restoration, mulching, and other issues in Northern California here.
Generally, the small drilled logs in the bee hotel are for carpenter bees that like to tunnel, and the packed honeycombs are for the leaf cutter bees (Osmia sp.) that like to munch their way into a nest.
We also saw California lady beetles (Coccinella californica), distinctive because of their lack of spots…
And nests for froghopper nymphs (Aprophora sp., aka spittlebugs) were all over the place!
As nymphs, froghoppers are very vulnerable to dessication and predation. As a defense they secrete a fluid and whip it into a froth (hence the name “spittlebug”), which helps them hide from predators, protects them from the elements, and keeps them from drying out. As adults, they become hard-bodied and less vulnerable.
And last but not least, many a syrphid fly was captured that day. Also called “hoverflies” because they tend to, well, hover in one place, they’re also bee mimics, as you can probably tell from the photo.
Aside from not having stingers, one thing that sets these bee mimics apart from the real thing is that they have only one set wings, not two (like bees do). In flies, the second set of wings have been modified into “halteres”, which allow the fly to perform all the quick acrobatics and direction changes we all know and love them for. Halteres are truly a fascinating piece of anatomy- you can read more about it here.
A giant thanks to Eddie Dunbar for being such an excellent guide and teaching us so much about insect world, and thanks to everyone who came out and enjoyed the day with us!