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!
September 9, 2013
Did you know there are small wasps here in Los Angeles that are potters? No, I don't mean some sort of weird waspish Harry Potter fan club—although that sounds like something I'd be totally into—I mean wasps that use mud to make miniature pots. Take a look at the craftsmanship, the sharply narrowed neck and that wide fluted rim, exquisite!
Photo taken by NHMLA Head Gardener Richard Hayden, with my fingertip for some perspective! This "pot" was constructed by a small wasp (one of those solitary wasps that are not prone to stinging us humans), which entomologists call potter wasps. However, this wasp wasn't just being artistic, she constructed this pot for a purely utilitarian function—it is actually a nest for an egg! A few weeks ago during a California Naturalist training, I spotted this beauty on one of our Baccharis plants in the Nature Gardens. Richard snapped a picture for me, as I was hoping there would be a way to identify the species of wasp that made this piece of pottery. I posted the picture to the Bugguide website, and had some luck! According to Ken Wolgemuth this nest was constructed by a potter wasp in the genus Eumenes, which literally translated from Greek means "gracious, kindly." Although if you were an immature moth or beetle, you wouldn't necessarily think so well of them. In fact you might find another explanation for the name more appropriate, even if it is less likely to be true. Some say the name is derived from Eumenides, the Greek winged goddesses of a vengence, and since these winged wasps provision their nests with caterpillars and grubs, it seems like poetic justice to me! After the nest has been constructed, the female wasp lays an egg, and then flies off to find and sting small caterpillars or grubs. The paralyzed prey is deposited in the pot alongside the egg, and the pot is sealed up. Which eerily reminds me of scenes from horror films where people are buried alive! Soon after the egg hatches and devours the still fresh insect meat, and then pupates. The adult wasp emerges to complete the cycle over again and lend a hand in controlling pesky moths and beetles in your garden! Dying to see what these wasps look like? Here's a picture to satisfy your curiosity:
Photo of a Floridian potter wasp, Eumenes fraternus, from What's That Bug website
January 4, 2013
Since tomorrow is the twelfth day of Christmas, I thought I'd give you your belated gifts. Of course they're all part of L.A.'s surprising biodiversity, yes even those turtle wasps! Twelve weevils wandering
Eleven pepsis wasps piping
Nine ground squirrels dancing
Eight ants-a-milking (though technically they should be milking aphids)
Six roaches-a-laying (down that is)
Five under wings
Four warbling birds
Three French (phorid) flies
Two turtle wasps
And a hawk in a pear infested pond
Wishing you a happy New Year...what urban nature will we find this year?
July 20, 2012
We found a new wasp species in the North Campus. The Great Golden Digger Wasp, Sphex ichneumoneous, is an impressively large (approximately one inch long), and active solitary wasp. Although many see a wasp this large and brightly colored—the orange and black combo usually tells us to "stay away"—this wasp is not aggressive and is very rarely observed stinging. Solitary Hymenopterous insects (those in the order Hymenoptera, aka bees and wasps) are not prone to stinging the same way social species are. This is because they don't have a hive to protect.
Great Golden Digger Wasp feeding on milkweed nectar The Great Golden Digger Wasp is actually a beneficial insect in our gardens. Here's how: They are great hunters. Their scientific name ichneumoneous, is Greek for tracker. Adults feed on nectar and are often seen foraging on flowers. When a female is ready to lay eggs, she digs up to six nests in exposed soil. When she is ready, she captures a cricket, grasshopper, or katydid (yay, pest control)! She paralyzes the insect by stinging it, and then takes it to the nest. When she gets back to the nest, she goes in to check that everything is okay. She then emerges and drags the paralyzed insect into the hole. There she lays one egg on each paralyzed insect. The eggs hatch after two to three days and begin to feed on the paralyzed insect. After a few weeks to many months (depending on the time of year the egg was laid and the weather) the larvae metamorphose into adults and carry on the divfe cycle. Free Will Hunting In the 1980s, cognitive scientists, Daniel Dennett and Douglas Hofstadter, used these wasps' unthinking deterministic (aka pre-programmed) behaviors to illustrate the meaning of free will. As described above, female S. ichneumoneus, check their holes before dragging the paralyzed prey item into it. Scientists tested this behavior in a controlled environment by moving the prey item while the wasp was inside the nest. When the wasp emerged, she would relocate the prey, drag it back to the nest, and then check the nest again (even though she had already done it very recently). The experiment was repeated up to 40 times, and each time the wasp would re-check the nest. In Dennett's 1984 book, Elbow Room, he used this behavioral study as an analogy to the opposite of free will (coined sphexish by Hofstadter), i.e. futily repeating the same actions over and over again in a pre-programmed manner. In contrast, we humans have the ability to recognize futile behavior, exercise our free will to change something, and hopefully disontinue futile activities. YAY! He even coined the term antisphexishness, the state of free will. Try dropping that one in your next conversation with an intellectual and see what happens!
September 12, 2011
When Tim Bovard, the Museum's taxidermist, told me about getting stung by wasps on the fourth floor patio, I had to investigate, especially since I sometimes eat lunch up there. During a much needed afternoon break from my computer, I went in search of the offenders. What I found on my afternoon foray were some large and impressive nests, definitely worthy of a blog entry. So of course I asked Sam if he would take pictures for me, and I went to work identifying them.
Common paper wasp nest, Polistes exclamansThe species living on our patio are Common Paper Wasps, Polistes exclamans, which have a widespread distribution through much of the southern United States. These insects construct a papery nest from fibers they gather off dead wood or plant stems. Next time you see a paper wasp on a wooden fence realize it might be chewing off tiny pieces of wood which they will mix with their own saliva to make paper! The nests are umbrella shaped and generally built under eaves or porches, or in similarly sheltered locations. Unlike yellowjackets and hornets, paper wasp nests are not enclosed in a papery shell, which give a really good view into the individual cells.
A view into a brood chamber, can you see the larva?Sam was also able to get some great video footage of the wasps at work. In an effort to provide the best video documentation ever, Sam nearly sustained a few stings himself. Luckily the wasps went for the video camera instead!
August 5, 2011
A couple weeks ago we had the second round of our North Campus insect survey. Fifteen Museum staff tromped around the North Campus to see what insectuous wonders we could collect. Although we found some notably large specimens, the largest being a 3-inch bird grasshopper (Schistocerca sp.), the most interesting find was actually something a lot smaller. Much, much smaller in fact: a minute fig wasp about 2 millimeters in length!
Female Fig Wasp, Pleistodontes sp. Fig wasps belong to the wasp family Agaonidae and as their name implies, they have a life history intricately linked with fig trees, family Moraceae. In fact fig trees can not produce figs without the wasps, and the wasps can't reproduce without the figs! The way this mutually beneficial relationship works is quite astonishing, especially if you take a journey to the core of a ripening fig! Journey to the Center of the Fig It all starts when a mature female fig wasp enters the synconium (an immature fig if you will) through its natural opening, called the ostiole. This sounds really easy when you think how small these wasps are, but nature has not made it easy on the fig wasp, as the opening is actually too small for the adult wasp to enter without damaging herself. It's so small that the fig wasp often loses her wings and much of her antennae as she struggles through the opening. To enable passage through the ostiole, the underside of her head is also equipped with spines that help to get a grip as she's going through the hole (see image above). Once inside the synconium she passes over the fig's female flowers and inadvertently deposits pollen from the male flowers of her original host tree. She then deposits her eggs in the cavity. Her business being done, she dies. The Pleistodontes fig wasp we found is, interestingly, not a pollinator of edible figs. Instead, it is a pollinator of ornamental figs which can be found in backyards and parks across Los Angeles. Once pollinated, the fig fruit begins to develop, consuming the wasp's dead body in the process. The eggs hatch and the larvae consume small parts of the developing fig. After the larva eat enough fig, they pupate and finally emerge as adult male and female wasps. The wingless male wasps have only two functions to perform in their short lives—to mate and to escape! Finding a mate inside the fig isn't too difficult for the male wasp as all of his sisters are stuck inside the fig with him (remember how small the ostiole opening is). After he mates with at least one of his siblings (or offspring from another wasp), he begins digging a tunnel to exit the fig. This tunnel is the escape route that the female wasp uses to exit the fig, but not before she picks up pollen from the male flowers. This pollen will eventually pollinate the developing fig she visits to lay her own eggs in, and thus the life cycles of both fig and fig wasp continue. All I can say is WOW! Nature is weird, wonderful, and so cool! Thanks to entomology curator Brian Brown for identifying and photographing the wasp.