Many of you don’t know that mosquitoes have a complex life cycle. OVMAP tries to take advantage of this by targeting the stage of development easiest to contain and thus, treat.

Picture: University of Georgia

From this diagram showing a typical standing water mosquito’s life cycle, you can see several stages. This is a complete metamorphosis, common among the Dipterans (the flies), the Order of insects mosquitoes belong to. With mosquitoes, all of the stages (besides the adult) require water to grow.

After mating and a blood meal, the female mosquito seeks out a suitable water source which to lay an egg raft, typically a couple hundred eggs.

Only female mosquitoes take blood. Now we’d all like to believe this is for some Hollywood vampire, post-coital, demonic blood lust, I mean, why else would something so devilish as a mosquito exist? But a closer look will reveal a more earthly, biological reason.  

With few exceptions, the protein from your blood is needed to produce each clutch of eggs she will produce during her lifetime. To seek out that obligatory warm snack, she can detect movement, sense exhalations in the form of carbon dioxide and lactic acid, or sense odors from long distances. Male mosquitoes typically feed on nectar from flowers and some play small roles in pollination.

The eggs she’s deposited will hatch, shortly after laying, into larval mosquitoes. The larvae breathe air through a siphon at the very end of their abdomen from the surface. They feed by relying on oral brushes to pull bits of organic matter into their mouths. So, they essentially hang upside down with an abdominal grasp on the surface tension of the water while they breath, then dive toward the bottom to feed and evade predators.

As they grow they will go through four molts, each one slightly bigger than the last. The growth rates of larval mosquitoes depend on the species, the amount of food available, and the temperature of the water. In mid summer, when temperatures are at their highest, growth rates from egg to adult can be less than a week leaving a very short window for larval control operations.

Pupation takes place after the larva reaches maturity. Inside the pupa massive changes are taking place, as the lava transforms into an adult mosquito. There is no way for the pupa to eat as even its mouthparts are changing into the piercing and sucking hypodermic proboscis we all know so well.

The pupa hatches into an adult the cycle begins anew.

So which of these stages of life would be the easiest to control? Well, the adults are out in the open air, the eggs are very small, only last a short time before they hatch, and hard to find, and the pupae don’t eat, leaving the larval mosquito as the target of choice.

Treating mosquito larva in the Owens Valley starts with finding those sources of water that raise mosquitoes. We live in a dry country and with a dry country comes irrigation. The DWP allotment of irrigation water for the irrigation season is 5 acre-feet per acre of land. The irrigation season starts April 1^st and extends to September 31^st. One acre-foot of water is an acre of land with a foot of water on it, or 43,560 cubic feet of water, or 325,851 gallons of water, or 2,718,144 pounds of water, or a lot of water, you get the point.

As the water spreads out over the land, the bulk of it does what it’s supposed to do and waters the feed for the cattle and nurtures the trees and other plant life in the valley. Some of it however, on its way into the ground, creates vast ponds that stay filled with water for weeks providing the best mosquito habitat on the east side. All the irrigated pastures provide the perfect sources for those female mosquitoes to lay their eggs in. Couple this with the vast stretch of river that run down the middle of this Valley and you have the 1700 square miles within the boundary of the Owens Valley Mosquito Abatement Program.

Oser says, “The river’s potential by itself has brought me to my knees in tears several times.”  A steady flow of 400 cubic feet per second is very controllable from a mosquito man’s standpoint, but throughout the year the river fluctuates due to snowmelt and summer storms, as any fisherman or worthy river “tuber” knows. If the flow reaches 600 cubic feet per second, the river spills its banks into thousands of eons-old river channels and oxbows forming stagnant ponds that can last for months.  Last year, the river section east of Big Pine was running at over 1000 cubic feet per second. This is why, despite our best efforts, mosquitoes will always be a part of mid-summer fishing down at the river.

With the re-watering of the Lower Owens, we anticipate, at least initially, similar large-scale mosquito hatches with the seasonal flow changes. We ask for a little patience as we seek out mosquito breeding sources and make them a part of our treatment schedule. 

To date we know of thousands of sources ranging in size from kiddy-pool size holes that big bulls dig to show their reproductive prowess, to multi-acre tule ponds, lots of them within a stones throw from schools and large neighborhoods. Many of you would be surprised to learn just how many millions of mosquito larvae are growing, every summer, so close to your own neighborhood.