Although the mosquito season comes to a close as the chill of winter approaches, fly season is in full swing as autumn’s temperatures ideally foster their abundant breeding.
“This time of year is perfect for flies to reproduce,” said UC Davis entomologist Lynn Kimsey, who heads the department of entomology. “And Davis is the perfect place.“
The common housefly, also known as Musca domestica, breeds in manure, sewage or any decaying object. For this reason, the surrounding fields and even the cows on campus are ideal breeding grounds for this common household pest.
Temperature is also a factor in the fly’s life cycle. California’s characteristically warm fall months allow flies to reproduce at an alarmingly fast pace.
“Flies at this time only live for about two and a half weeks but can deposit up to 150 eggs during that time,” Lynn said. “Their numbers will grow exponentially larger.“
Even though they only seem like pests, having the housefly around human food can carry significant health consequences.
According to the University of Rhode Island’s Landscape Horticulture Program’s website, the mouthparts of the fly are adapted for sponging up liquids and therefore cannot bite. To bypass this, they eat solid foods by regurgitating their saliva and stomach contents and then re-consume it.
“If a fly lands on that hamburger that you’re eating and had just came from a pile of feces, then that will be on your hamburger, as well as any bacteria in it and any bacteria on the fly’s feet,” Lynn said.
This method of feeding makes the common housefly an excellent carrier and transmitter of diseases to animals and humans. They are known to transfer at least 100 different pathogens and cause more than 65 diseases in humans, according to the URI’s website.
Many bacterial and viral diseases can be spread from flies to humans this way. They include Typhoid, cholera, salmonella, tuberculosis, dysentery, E. coli, parasitic worms and even infective hepatitis.
“The probability of a housefly infecting a human is not good, but there is still a propensity of transferring and flies remain an exceedingly important vector of infection transmission,” said Lynn’s husband Robert Kimsey, a UC Davis medical entomologist.
Flies can also infect domestic animals such as cattle and other animal products.
“Cows can eat the food flies have contaminated and be infected with E. coli in this way,” Lynn said.
The life cycle of a housefly has three stages: maggot, pupa and adult. A female housefly deposits its eggs in decaying organic matter. After a day or two, the eggs hatch creating worm-like maggots, which eat the decaying matter around them for nourishment. The maggots then pupate into a cocoon-like structure until they emerge as an adult fly. The whole process can be completed between one and three weeks.
The natural predator of flies in their egg state is the fly parasite. A fly parasite lays its own eggs in the fly egg, killing the fly before it even hatches.
Many agricultural sites use these fly parasites as a way to control the housefly population because they do not affect or bite animals and humans themselves, according to the U.S. Department of Agriculture’s website.
Some insects, birds and amphibians also act as predators of the housefly.
Humans have also developed other methods for preventing the transmission of diseases from houseflies, which has affected our current state of living.
“The development of window screens and indoor plumbing can be attributed to the housefly,” Lynn said.
In the earlier part of the century, there was a higher infant mortality rate because flies would come from the outhouse and land in the kitchen, contaminating food and bottled milk for babies, Lynn said.
Nowadays, besides trying to keep flies away from decaying organic material, the best way to control flies is to use boric acid in the bottom of dumpsters and use fly bait around adult food sources, according to Ohio State University Extension’s website.
If that does not work, there is always a fly swatter.
NICK MARKWITH can be reached at features@californiaaggie.com
