Mosquito hunting in Colorado

Last summer I had my first job as a seasonal field biologist, and my job consisted of larvicide. Not to fret, I was killing mosquito larvae, with the goal of controlling mosquito populations and reducing the risk of West Nile Virus.

The best way to control mosquito populations is by killing them while they are in their larval stage, because the pesticide we use is a naturally occurring bacteria attached to a corn husk that only killed mosquitoes. When the larvae eats the pesticide it destroys their stomach, which of course kills them.

So I was given a map and an area to work in, and went to many different irrigated fields, ditches, cattail marches and even an abandoned swimming pool that had become overgrown with cattails.

Nearly all of the places I went to were on private property, and a few were Boulder County Open Space areas.

I would use a dipper (essentially a cup on a stick) to check the water to see if there were any mosquito larvae, and if there were I would then throw a certain amount per acre of pesticide down. The larvae would eat this, and would often be dead by the next day.

This was a very interesting job, where I got to see a lot of things I never would have, including lots of animal bones, snakes, owls and the occasional irate home owner who thought I was there to kill his fish.

Here are some pictures of some of the interesting things that I cam across:

Bones, I found a lot of bones on this job, all some kind of animal (no human, don't worry!) from fish bones to rodent, I found a lot!

I think that these bones are from a carp (a fish)

What strange creature did this come from?!

It's very small! The teeth are long and orange, which means that this is probably some kind of rodent scull. All rodents have front teeth that never stop growing and have to constantly be shortened! 

 Some things look like mosquitoes but really aren't.

I stepped into some long grass and these midges flew up. They look like mosquitoes at first glance, but midges form a tight swarming cloud when bothered, and mosquitoes don't.

 If I wasn't upsetting the killdeer, I was upsetting the red-winged black birds, both of which usually had nests near where I was working.

It was always the male who complained and flew over my head. The female red-winged black bird, which is brown with stripes, never bothered me.

 I found lots of amazing aquatic life!

A young crayfish! (Or crawdad if you call them that)

Great Plains Toad

A Tiger Salamander, Colorado's only species of salamander!

The one on the left is a damselfly naiad, and the one on the right is a dragonfly naiad. Dragonfly larvae tend to be bigger and the three tail-like gills tend to be short or nonexistent. Damselfly larvae have three long gills and are smaller and slimmer.

I believe this ferocious looking larvae is a dobsonfly larvae, but I'm not 100% sure.

I saw a LOT of tadpoles. I think that these are toad tadpoles, every now and then I found some really huge tadpoles that I'm pretty sure were bullfrogs, an invasive species.

Fairy shrimp!  These were the coolest thing to see! Fairy shrimp are vernal pool species, and are highly adapted to survive in small ponds that exist in the spring but are gone by midsummer.

I stumbled onto some tiny holes near a pond, and saw a crayfish pop out! I'd never seen this behavior before, so it was pretty interesting!

I suspect that these might be used for mating purposes, or perhaps the small holes near the water are just where they lay the eggs. 

I saw some amazing things out of the water, too!

White Pelican

Great Horned Owl

Eastern King Bird

Mule deer

American Kestrel

A strange tree that I never figured out . I've never seen so many thorns on a tree before! 

Here are the leaves in the tree. I thought it might be a Hawthorn until I saw the leaves. 

I found a lot of cool insects! 

This is a plains garter snake. I saw a LOT of these.

They seemed to like hunting near the water, i saw them in areas like this the most.

Cormorants on a tree

A milkweed beetle on some milkweed

I'm not sure what kind of beetle this one is.

Most of the summer all you can hear are cicadas. I FINALLY found one in a bush and managed to get a picture!

I also found several praying mantises! These guys are AWESOME. 

I found my very first owl pellet!

And this is likely the owl that is came from!

Belted Kingfisher

This spider is a decent size, maybe three inches? I don't hate spiders but this guy made me a little uneasy to see. It had it's own tunnel too.

I was startled by a few bull snakes, and only got one picture of a live one. 

Someone ran over this bull snake, and I always get really mad when I see that. There was no reason for this snake to die.

Here I am next to the poor dead snake for size comparison. It was about four feet long. 

Mosquitoes lay eggs in a lot of different places, some places were hard to find. The worst were cow pastures, where the cows would leave small but deep hoof prints in the mud. Each individual hoof print became prime real estate for breeding mosquitoes. There's no natural predators, they warm up fast, and they are harder then hell to locate so often times a few patches might go undetected if you try to treat by hand.

The cows liked to eat the pesticide that we put down. It's harmless for them, but discouraging when they eat all the pesticide before the mosquitoes do, so it's like you didn't treat the area at all.

A single hoof print hole, filled with mosquito larvae.

An abandoned pool, loaded with mosquito larvae

This field had some puddles that were near constant mosquito breeding grounds. 

Flood irrigated fields are also great mosquito breeding habitats. Usually after floods there is a boom in the mosquito populations, which explains why a dry state like Colorado has so many mosquitoes. A lot of farmers use flood irrigation on their fields because it's cheap, even if it wastes water and creates huge mosquito habitats.

This was supposed to be a field, but the reservoir's water was high this year.

Cattail marches are also a great mosquito breeding habitat, but they are also home to many mosquito predators like dragonflies and frogs.

One day my awesome coworker was helping me with a few sites, and a huge storm rolled in. We waited in the car while it hailed.

The hail. Good thing we were near the car!!

Now for some mosquito facts!!

First, what do they look like?

Mosquito larvae have big heads and no legs. They have a breathing tube on their rear ends, so often you will see them at the surface. When a shadow passes over the water, they dive down to avoid predation.

Sometimes called "wigglers" as that's how they move. They wiggle. The third life stage is called a pupae, and they look like alien spaceships. These are harder to kill as they no longer eat, but they still need to breathe. If we see pupae we have to use an oil (a mineral oil) to kill them.

Some mosquitoes lay their eggs in areas that are commonly flooded, like a field that is irrigated with flood irrigation. When the eggs are wet, they hatch and there are at least thousands (though the number is probably more in the millions) of mosquito larvae hatched at once.

Here is a squished female that managed to get a meal out of me first. They have two wings (they are in the fly family Diptera, and all flies only have two wings) A long proboscis (their biting mouth part) and six legs (like all insects!) The males don't have a biting mouth part like the female, and have feathery antenna. 

 WHY MOSQUITOES ARE BAD NEWS:

Mosquitoes don’t just bite and annoy you, although I can think of no sound more frustrating than the buzzing of a mosquito in your room after you’ve turned out the lights. Mosquitoes are the number one deadliest creatures on Earth, killing more humans than all of the fatalities in all of our wars combined.

They are a vector (that means a carrier) of deadly diseases from malaria to dengue, and they kill millions of people world wide each year.

Mosquitoes have 4 stages in their life cycle, the first three occurring in standing water. In places like Colorado where the water temperatures can get to the optimal warm temperature for mosquitoes, they can go through their first 3 life stages in as little as five days.

A single mosquito can lay up to 250 eggs at a time, which on average take seven to ten days to hatch. In ideal temperatures with lots of food, they can hatch in five days.

OTHER MOSQUITO FACTS:

• Only the females bite, and the males eat nectar. The females need the blood to lay eggs.
• The word “mosquito” comes from the Spanish word meaning “little fly”
• Only a certain species of mosquito carries West Nile Virus, the Culex species. They are most active during dawn and dusk, so it is fairly easy to avoid them.
• Anopheles is the species of mosquito responsible for carrying Malaria, and like Culex they are more active during the dawn and dusk.

HOW YOU CAN HELP PREVENT BREEDING:

The American mosquito control association recommends using ‘The Three D’s” to protect yourself and prevent mosquitoes from breeding on your property.

• DRAIN- mosquitoes can lay eggs in nearly any standing water no matter how small, so make sure you don’t have anywhere where there might be standing water. If you have standing water somewhere, drain it! If you have something like a bird bath or water for cattle, make sure you change it regularly to prevent mosquitoes larvae in the water from reaching their adult stage. Mosquitoes can lay thousands of eggs in something as small as a Frisbee, so keep an eye out for these potential breeding spots!
• DRESS- wearing light colored, loose fitting clothing helps keeps off these blood-sucking monsters. Studies have shown that some of the 174 mosquitoes that live in the United States are attracted to dark clothing, and most mosquitoes can bite right through tight clothing. If there are a lot of mosquitoes out, try and wear long sleeves and pants.
• DEFEND-Use a mosquito repellant that has been registered by the Environmental Protection Agency. These have been tested and shown to have minimal risk for human safety when being used. Four of these are DEET, Picaridin, Oil of lemon eucalyptus, and IR3535. Always make sure to keep repellant out of your eyes and mouth, and adults should apply mosquito repellant on their young children, rather than have the child do it themselves.

Only a certain species of mosquito carry West Nile Virus, and another kind carries Malaria. Should you find yourself in an area where these are known to occur (West Nile is a problem in most of the United States) avoid going outside at dawn and dusk. This is when both of these species of mosquito are most active. Be sure to wear long sleeves and loose fitting clothes should you need to be outside, and wear mosquito repellant!

If you have a fishpond, or a cattail marsh, there are some natural mosquito killers to be aware of! However, while natural mosquito predators do exist, they simply don’t eat enough to keep mosquito populations under control.

• Dragonflies - both dragonfly larvae and the adults will eat mosquitoes! The larvae are better at eating mosquito larvae then the adult dragonflies are at eating adult mosquitoes. This is partly because the adults have a wider selection of things to eat, and also they tend to eat more during the day when adult mosquitoes are resting in the shade.
• Damselflies- the daintier ‘brother’ of the dragonfly, also feeds on both larval and adult form of mosquitoes, but they are not the voracious predator that the dragonfly is.
• Gambusia Affins- also known as the mosquitofish is an effective predator of mosquito larvae.
• Purple Martin- This bird is a great mosquito hunter, but the amount of mosquitoes a purple martin eats is often exaggerated. While they certainly can eat mosquitoes in large quantities, they would much rather eat something larger and more filling, like a June bug or moth. They also prefer eating dragonflies, which is unfortunate as they are another mosquito predator.
• Bats- Just like the purple martin, they have the potential to eat thousands of mosquitoes but they would prefer a juicier, larger meal.
• Frogs- frogs, toads and tadpoles can also eat mosquitoes. The adult toads and frogs are more likely to eat mosquitoes than tadpoles are, as tadpoles are mostly herbivorous eating plants and algae, while some larger tadpoles might still snack on the occasional mosquito larvae.

Supporting any of these animals vie birdhouses, fish ponds or bat houses, can help with mosquito control, but it’s not enough by itself. The most important thing is to reduce and eliminate standing water.

SOURCES:

American Mosquito Control Association

http://www.mosquito.org/

Fight the Bite Colorado

http://www.fightthebitecolorado.com/

West Baton Rouge Parish Council

http://www.wbrcouncil.org/Departments/Mosquito-Abatement/Natural-Mosquito-Killers