We know it works, but how?

Just how does DEET work? Does it jam the senses of a mosquito? Does it mask the smell  of the host?

You spray the chemical repellent on your arm and thankfully, those darn skeeters leave you alone.  They need a blood meal to develop their eggs, so off they buzz to find another host, one that's not so inhospitable.

But why do mosquitoes avoid DEET?

Well, they avoid it because it smells bad to them. Yes, they can smell it--that's why they avoid it.

The groundbreaking research, the work of UC Davis chemical ecologist Walter Leal and researcher Zain Syed, is published today in the Proceedings of the National Academy of Sciences (PNAS), which lifted the news embargo at 2 p.m., Pacific Standard Time.

The research contradicts a Science article published in March by researchers at Rockefeller University, New York. The researchers, as other scientists have long believed, said mosquitoes can't smell DEET because it jams the odorant receptors in insect nervous systems.

The Leal-Syed research solidly establishes the real mode of action.

Noted entomologist James "Jim" Miller of Michigan State University praised the Leal-Syed work as correcting “long-standing erroneous dogma.”

Said Miller: "For decades we were told that DEET warded off mosquito bites because it blocked insect response to lactic acid from the host -- the key stimulus for blood-feeding. Dr. Leal and co-workers escaped the key stimulus over-simplification to show that mosquito responses -- like our own -- result from a balancing of various positive and negative factors, all impinging on a tiny brain more capable than most people think of sophisticated decision-making.”

“This new work corrects long-standing erroneous dogma, and shows that recent work on DEET mode-of-action published in the flagship journal, Science, apparently was flat-out wrong,” Miller said. “One of the great attributes of science is that, over time, it is self-correcting."

Leal, past president of the International Society of Chemical Ecology  and former chair of the UC Davis Department of Entomology, said previous findings of other scientists showed a “false positive” resulting from the experimental design. 

Now that we know that skeeters can smell it, this will no doubt lead to better methods of insect control. Or, as Major Dhillon, president of the American Mosquito Control Association and district manager of the Northwest Mosquito and Vector Control District, Riverside, said: ”In the future, this new knowledge can be incorporated into developing new repellents and may be in control strategies for Culex quinquefasciatus and other mosquitoes.”

Those darn female mosquitoes, always in a “Let-us-prey” mood, have clearly met their match: the "why" behind "Let us spray."

“The war is over—again,” wrote reporter Pat Brennan of the Orange County Register in a news article published Aug. 14.

Brennan was referring to the war against the Mediterranean fruit fly, a tiny pest that targets some 260 crops. The pest, first detected inCaliforniain 1975, prefers such hosts as peach, nectarine, apricot, avocado, grapefruit, orange and cherry. It is considered the world's worst agricultural pest.

California State Department of Agriculture had earlier announced the eradication of the medfly in three counties:Los Angeles, Solano andSanta Clara.If it were to become permanently established in California, the medflycould cost the state  $1.3 to $1.8 billion in annual losses,  estimated CDFA Secretary A. G. Kawamura.

I remember whenSolanoCountyag officials discovered four live medflies in a single trap in downtownDixon. The date:  Monday, Sept. 10, 2007. Newspapers bannered the story. A quarantine ensued.   Farmers fretted, and rightfully so.  Later I attended a press conference at theNutTreeAirport, Vacaville;a pilot had just released the first of many millions of sterile male fruit flies over Dixon. He showed us the  sterile medflies, dyed pink.

The sterile flies mate with wild flies and biologically force wild populations out of existence, the CDFA says.

UC Davis entomologist James Carey, who has published widely on the medfly, said the pest has been multiplying and spreading undetected--like cancer--for years in California.  He says it's never been really eliminated and he questions whether it could ever be eradicated.

CDFA and Solano County ag officials said no; that an errant tourist likely brought it to Dixon on a piece of fruit fromHawaii. The medfly lays its eggs inside fruit.

Medfly wars ensued.

Carey shared an email he sent Aug .14 to Brennan:

“The absence of medfly appearances anywhere else in the continental U.S. besides California over the past two decades strongly supports the argument that the medfly has never been completely eradicated in our state. CDFA's efforts at eradication have been successful at driving the populations back to subdetection levels for a few years. However, the reappearances of the medfly in the same cities and even in the same locations within these cities is due to a long-term established population.  Although I fully acknowledge the need to respond to the medfly when it appears in the state as it did last year, I have no reason to believe that this program will have been any more successful than the previous ones which merely suppressed rather than eliminated the medfly population from the state."

“This recent declaration of eradication is around the 50th emergency response to medfly outbreaks over the past two decades by CDFA, virtually all of which have been in the same general locations. To my knowledge during this same period no other state such as Arizona, Florida or Texas has experienced any outbreaks even though these states, like California, have climates suitable for the medfly establishment and have many tourists and migrants who are capable of introducing the medfly. These states have experienced no outbreaks while California has experienced 50.”

The CDFA Web site says medflies are not established in California. 

"These (medflies) and other exotic pests have not become established in California due to (1) strict federal exterior and state interior quarantines, (2) a pest detection program, and (3) aggressive eradication programs when an infestation is discovered."

Carey, who has plotted all medfly finds in California, says medfly populations  “do not really get going until late summer and fall. Stay tuned for this fall.”

One thing is certain: the little bugger draws a lot of attention. That's because, as Brennan wrote, it “attacks so many crops.” 

“I've got black bumblebees buzzing around our backyard like crazy,” the caller said. “They're loud. Very loud. They're dive-bombing and scaring the cat and dog. I've never seen anything like this before.”

The unwelcome visitors were not bumblebees. They were carpenter bees.

Carpenter bees? No, they don't know how to read blueprints or frame floors and walls. They nest in weathered wood, like your fence posts, utility poles or firewood. They tunnel into your deck, railing, shingles and shutters. 

They are pests.  But they're also pollinators. Native pollinator specialist Robbin Thorp, professor emeritus at the UC Davis Department of Entomology, fields many calls about carpenter bees.

This one pictured below is a male carpenter bee,  Xylocopa tabaniformis orpifex Smith NB, Thorp says. It is stealing nectar from the base of the flower.  They also spend a lot of time cruising around chasing everything that enters their territory.”

Contrary to popular opinion, carpenter bees don't consume wood.  If you don't want them around, paint or varnish your wood. You can also plug their (unoccupied) holes with steel wool or caulk, or screen the holes so they don't return.

The female and male carpenter bees that nectar the salvia (sage) in our bee friendly garden are about the size of bumblebees. “Robust” comes to mind.  Okay, fat. They're fat.  

Their abdomens are bare and a shiny black. If you photograph them, you'll see your own reflection. It's like seeing your reflection in a black Lamborghini.

The female carpenter bees are a solid black, while the male carpenter bees are lightly colored around the head.

In comparison, bumblebees have hairy abdomens with at least some yellow markings.

If I were a carpenter and you were a…nah, I'd rather be a bumblebee. 

Ouch! So, you've been stung by a bee.

If you're a beekeeper, an occasional sting is a natural part of beekeeping.

UC Davis apiculturist Eric Mussen says that the average beekeeper may be stung approximately 3000 times a year.

Mussen describes the sting as a “modified egg-laying apparatus,so only females can sting.” The queen bee can sting multiple times, while the female worker bee dies after stinging. Drones, or male bees, cannot sting. (Interesting that Jerry Seinfeld, who played the role of Barry B. Benson in The Bee Movie, could sting! Then again, he was a "pollen jock," too. However, only the worker bees (females) gather nectar and pollen.)

When bees sting, they inject a venom that can be temporarily painful. The pain may last a few minutes but may be felt up to a few days later.

How do you remove the stinging apparatus? “It doesn't matter how you get it out as long as you remove it assoon as possible, within 45 to 60 seconds,” Mussen says. “Otherwise, venom will keep pumping into the body.”

He advises victims to "pull out or scrape off the sting (which some people call a “stinger”) with a fingernail. The sting is barbed. The sting also emits an alarm pheromone that marks the target for additional stings. Leave the area quickly.”

Some advise that you wash the wound and treat it with ice or a cold compress to alleviate the pain. Or, apply an aerosol or cream antihistamine preparation that contains a skin coolant. The important point: don't scratch the itch as that could lead to an infection, Mussen says.

If you're stung on the neck or mouth, or start feeling severe symptoms, you should seek medical attention immediately, he says.

Allergic responses include hives, swelling, nausea, vomiting, abdominal cramps and headaches. Life-threatening reactions—which require immediate medical intervention—include shock, dizziness, difficulty in breathing, unconsciousness, and a laryngeal blockage resulting from swelling in the throat.

“Only about one or two people out of 1000 are allergic or hypersensitive to bee stings,” the UC Davis apiculturist says.

To avoid being stung:

• Don't walk in front of a hive as you're in the bees' flight pattern.
• Wear long pants and a long-sleeved shirt.
• Wear light-colored clothing. Bees are more likely to sting black or red objects.
• Don't wear perfume, cologne or scented soaps.
• Avoid going barefoot.
• Remain calm if you're stung. Don't flail your arms at the bee; movement attracts more stings.
• Remove bees from a swimming pool before entering the pool.