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The Bugs of Summer

May 14, 2014

Despite popular misconception, New Jersey is not a mosquito-infested swamp. My backyard in Northern New Jersey is not notably infested, although there's always the general fear of tick-borne Lyme disease, and eastern equine encephalitis from a rogue mosquito. Our frigid winters tend to eliminate the many insect pests found in the Southern States.

Aedes aegypti mosquitoThis small insect, the Aedes aegypti mosquito, has changed the course of human history through its transmission of yellow fever viruses, and other diseases.

(Illustration by August Goeldi (1859-1917), via Wikimedia Commons.)

Mosquito repellent devices have been sold from the earliest days of electronics. They're all based on the idea that mosquitos are repelled by a high frequency tone at the limits of human audibility, about 15 kHz. Although any high frequency tone would annoy humans, and perhaps mosquitos, the idea is that certain insect predators of mosquitos beat their wings at that frequency.

As they say, it looks good on paper, but do these mosquito repellent devices work? A recent study by the Cochrane Collaboration, an international healthcare collaboration, showed that the devices don't work.[1-2] As written in their report, "There was no evidence in the field studies to support any repelling effects of [electronic mosquito repellents], hence no evidence to support their promotion or use."[1]

There's a complementary high frequency device, called The Mosquito, for the prevention of loitering by young people. The idea of this device is that its tones are only audible to younger people.

555 Timer Mosquito Repellant Circuit (Not Valid Science)Here's my 15-minute design of a simple mosquito repellent circuit.

Many electrical engineers of my generation built similar circuits, since there's a good story behind its working principle, but scientific studies have invalidated the concept.

(Illustration by the author using Inkscape.)

I've mentioned in previous articles that science advances not just through theory, but by development of new instruments with which to test these theories. A prime example of this is Xray crystallography, which led to the structure of DNA and a revolution in biology. When your objective is the protection of humans, animals and crops from insect pests, it's important to know what you're fighting.

Over the decades, some inexpensive sensors have been developed for classification of flying insects, but these haven't had a lasting impact.[3] A team of scientists from the University of California, Riverside, has been developing a multi-sensor approach to overcome the limitations of past work, which focused on just wingbeat frequency and limited datasets.[3-4]

The UCR team includes Yanping Chen, a computer science graduate student at UCR and lead author of the study, Eamonn Keogh, a professor of computer science and engineering at UCR, Adena Why, a UCR entomology graduate student, Gustavo Batista of the University of São Paulo (Brazil), and Agenor Mafra-Neto of ISCA Technologies (Riverside, CA).[4]

The UCR sensor also uses wingbeat frequency, but it uses an optical method of detection that allows extraction of additional data such as flight behavior patterns.[3] This allowed a Bayesian classification approach which is enabled by tens of million data points obtained by dozens of sensors operating in parallel 24 hours a day over the course of three years.[4]

bug boxPandora's Polyethylene Box

Test apparatus used by University of California, Riverside, researchers for collecting data on insect behavior.[4]

(UCR photo by Peter Phun.)

The sensor obtains data from insects flying through a light curtain, as seen in the photograph. A light beam passing from a laser diode to an array of phototransistors detects the acoustic signature of the insect wingbeats as small amplitude changes.[4] Interestingly, the prototype sensor was constructed with Legos®, a 99-cent laser pointer, and components harvested from a television remote control.[4]

Professor Eamonn Keogh with flying insect sensor.
Left, professor Eamonn Keogh holding his flying insect sensor. Right, detail of the sensor showing the light curtain in the flight opening. (Still images from a YouTube video.)

With two species of flying insects, the UCR sensor had 99% accuracy, declining to 96% for five species and 79% for ten species.[4] In one experiment, wingbeat frequency alone gave 88% accuracy, but adding time of day increased the success rate to 95 %; and, to 97% when location data were added.[4] The research team speculates that accuracy will be improved by adding other variable, such as the height at which the insects fly, temperature and humidity.[4]

Mosquito wingbeat audio spectrum
The reason why wingbeat frequency alone is not enough. There's considerable overlap of frequency of the species, Culex stigmatosoma and Aedes aegypti. (Fig. 1 of ref. 3, via arXiv.)

The goal of this research is the development of an inexpensive wireless instrument that's as effective as the current methods such as sticky traps and interception traps, but with the added advantage of being more accurate while reacting in real time.[4] Says Keogh,
"We set out not knowing what was possible... Now, the problem is essentially solved. We have created insect classification tools that can outperform the world's top entomologists in a fraction of the time."[4]
The team's plan is to deploy the sensor more widely than its present trial sites in Brazil and Hawaii. Tovi Lehmann, an entomologist with the Laboratory of Malaria and Vector Research at the National Institute of Allergy and Infectious Diseases (Rockville, Md.), is working with the team to deploy the sensors in Mali.[4] This research was supported by the Vodafone Americas Foundation, the Bill and Melinda Gates Foundation, and the São Paulo Research Foundation.[4]

The title of this article is a play on The Boys of Summer, a 1984 song by Don Henley. You can hear a live rendition of it, on YouTube, here. The song is apparently about lost youth and entering middle age, but baseball players are also called the boys of summer.

References:

  1. Ahmadali Enayati, Janet Hemingway and Paul Garner, "Electronic mosquito repellents for preventing mosquito bites and malaria infection," the Cochrane Library 2010, Issue 3.
  2. William Kremer, "Ultrasound mosquito repellents: Zapping the myth," BBC World Service, December 10, 2012.
  3. Yanping Chen, Adena Why, Gustavo Batista, Agenor Mafra-Neto and Eamonn Keogh, "Flying Insect Classification with Inexpensive Sensors," arXiv Preprint Server. March 11, 2014)
  4. Sean Nealon, "Saving Crops and People with Bug Sensors," University of California, Riverside, Press Release, April 29, 2014.
  5. Living the Promise: Eamonn Keogh, University of California, Riverside, YouTube Video, April 9, 2012.

Permanent Link to this article

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