August 15, 2017
What do you love most about summers in L.A.: picnics on the beach, Griffith Park barbecues, camping in the mountains, eating hot dogs at a Dodger game? I love summers for those reasons, too, but it is also my favorite time of the year to look for insects, a lifelong obsession I can’t seem to shake. Most bugs are busy doing whatever they need to do to survive without any trouble to us humans, but sometimes uninvited insect guests show up to our summertime celebrations and help themselves to our burgers and carnitas tacos.
The biggest culprits are wasps that naturalists call yellow jackets, although I have heard people refer to them as “meat bees,” (as well as some other names I cannot mention in polite company). Yellow jackets are indeed a huge nuisance at barbecues and birthday parties; they come very boldly in large numbers to bite off pieces of meat. If a person gets in their way, they can produce a painful sting, about the same strength as a honeybee sting, but unlike honeybees, yellow jackets can sting repeatedly.
I have become so accustomed to seeing them eat “people food” that I was intrigued when I recently saw a photo on iNaturalist of yellow jackets systematically eating a Southern Pacific rattlesnake down to the bone. Yellow jackets are opportunistic predators that usually hunt spiders, and other insects like caterpillars, but they will also scavenge protein where they can find it. Whether that is a dead cow in our burger, or a dead rattlesnake on the ground, meat is not to be passed up as it is essential for the survival of their colony.
Like some other species of bees, wasps, and the majority of ants, yellow jackets have a queen. The yellow jacket queen emerges in the spring, constructs the nest from wood fibers, lays her eggs, and begins to hunt for insects and spiders to feed her offspring as soon as they hatch. Once her infertile daughters are fully grown, they will carry on as workers by providing protein sources to their younger sisters while their queen stays in the nest to lay more eggs. Males are around only in late summer to mate with potential future queens, who will start new colonies the following spring. This means that the yellow jackets you see hunting in your gardens, scavenging carrion on trails, or helping themselves to your barbecue are females that are working hard to feed their little sisters.
In the process of collecting food, yellow jackets help to keep insect populations in check, acting as what gardeners call “beneficial predators,” but they also play an important role as part of the clean-up crew of the natural world. Along with some species of beetles and flies, yellow jackets are helping to recycle nutrients by scavenging dead animals. They are even important to forensic entomologists, scientists who analyze crime scenes by studying the insects that visit corpses. Carrion feeding insects only feed on dead animals at certain stages of decompostion, so identifying the insects can serve as a clock for investigators to approximate when death occured. In studies conducted with pigs to understand the role wasps like yellow jackets play in breaking down decaying animals, researchers observed wasps clipping pieces off of pig’s ears. No wonder yellow jackets are lured in by the smell of cooked hot dogs, pig parts rolled up in a tasty, easy to bite off bundle! As predators and scavengers, yellow jackets are willing to eat a wide variety of meat, not unlike some humans. Maybe this common ground will help us to make peace with these uninvited summertime guests.
“Yellow jackets and Paper Wasps.” Landolt, Peter J. and Arthur L. Antonelli.
“Occurrence of Hymenoptera on Sus scrofa carcasses during summer and winter seasons in southeastern Brazil.” Gomes, Leonardo et al.
Special thanks to Patrick Gavit and Gary Woo for their amazing photo submissions, and to Dr. Greg Pauly who shared them with me!
January 10, 2017
The Museum's Nature Gardens continue to be the gift that keeps on giving by providing precious habitat to wildlife living in the urban core of LA. Last November, we not only had our second alligator lizard sighting, but we also uncovered a rarely seen flower fly from our Malaise trap that collects insects as part of the BioSCAN project. This project has examined over 2,000 flower fly specimens representing 35 species in LA so far, but this rare fly from the garden, Myolepta cornelia, is the only one we have seen so far!
Before you dismiss this finding as “just another fly,” take a minute to ponder the many talents of these mini-marvels. Faster than a hummingbird, clocking in at 250 wing beats per second (!!!), flower flies spend their day revelling in the garden’s floral buffet. They can fly backwards as easily as they do forwards, or can be spotted hovering perfectly still in mid air, like little meditating, levitating yogis. Just like the beloved bee, they pollinate the flowers they feed upon. In fact, as hymenopteran (the bee, wasp, and ant group) mimics many are mistaken for a wasp or a bee, a trait that offers protection from potential predators.
Their ecological importance does not end there. As wee little fly babies (the maggot or larval stage, in other words), they act as beneficial predators or decomposers, depending on the species. The activity of the larva of our rare special fly M. cornelia is still a mystery to entomologists! We know that many of their close relatives feed on rotting wood in the larval stage and have a preference for oak woodlands, so it is possible that M. cornelia is helping to break down dead wood in the Nature Gardens.
Special thanks to Jim Hogue and Martin Hauser for their identification skills and syrphid fly insight!
Brown, Brian, James N Hogue and F. Christian Thompson. "Flower Flies of Los Angeles County". Natural History Museum of Los Angeles County. 2011.
Reemer, Menno, Martin Hauser and Martin C. D. Speight. "The genus Myolepta Newman in the West-Palaearctic region (Diptera, Syrphidae)." Studia dipterologica 11 (2004) Heft 2: 553-580.
December 23, 2013
Let's celebrate another year of L.A.'s AMAZING BIODIVERSITY. The benevolent blogger that I am, here are your gifts: Twelve Rattlers Rattling
Eleven Potter Wasps Piping
Ten Flies Decapitating (decapitating ants that is)
Nine Dragons Dancing (in the L.A. River)
Eight Mantids a Milking
Seven Planarians a Swimming
Six Lizards a Laying
Five Foxes Ring-ding-ding-ding-dingeringeding!
Four Glowing Worms (yes, they're glowworm beetles)
Three French Opossums
Two Turtle Newts
and P-22 in the Hollywood Hills
Here's to another year full of amazing Los Angeles nature discoveries! *P-22 image courtesy of the Griffith Park Connectivity Study