Mosquito of the Month: Aedes pullatus – the Alpine Snowmelt Mosquito

Mosquito Species Deep Dive

High in the Rocky Mountains, under the snow and ice, eggs that were laid by mosquitoes last summer lay dormant, waiting for spring. As soon as the ice becomes liquid, the first of the eggs will hatch. 

Known as the snowmelt mosquitoes, these species have a short season in which to grow. In order to get a head start, the larvae are adapted to survive in very cold water, including snowmelt ponds and overflow pools from frigid mountain streams. The cold water slows down their metabolism as well as their development into a flying, biting adult mosquito, which can take several weeks.

One of the most widespread, and arguably most beautiful of these cold-adapted species, is the Alpine Snowmelt Mosquito, Aedes pullatus. This mosquito is often abundant throughout the summer in mountainous areas of western North America, Europe, and Asia. They occur mainly in higher elevations, although also found less commonly as low as sea level in the colder northern latitudes.

Yes, I did say “arguably most beautiful.” Most of the high altitude mosquitoes are primarily black-scaled with only a few scattered patches of pale scales, their dark coloration perhaps being an adaptation for maximizing heat absorption. Aedes pullatus is also primarily dark-scaled, but is adorned with white, golden, and yellow patches of scales on the top and sides of its thorax. The top of their abdomen also has distinct white-scaled basal bands on each segment. On a microscopic scale, these mosquitoes stand out from most other mountain species – beautiful.

Snow doesn’t melt all at once, and often pools created by the first melting snow on sunny spring days will again freeze by cold night temperatures or late spring snow falls. Few animals can survive this repeated freezing and thawing, but I have found these alpine snowmelt mosquito larvae in the spring by chipping away at an ice-covered pond. Under the ice they were moving slowly but very much alive.

Adults emerge throughout the summer. Males of this species have been reported to hover in great swarms just after sunset, often over a boulder or other solid landmarks in a forest opening, waiting for a receptive female to fly through the crowd. The resulting scramble results in one fast, lucky male getting to mate with her and father her next set of eggs – it isn’t known whether the female mates only once or if they seek out other males in the future. We also don’t know how long they live, or how many eggs females may lay in their lifetime.

larval-mosquito-habitat-aedes-cataphylla-5_rockies-CO_kelseyrIn fact, relatively very little is known about the biology and behavior of alpine snowmelt mosquitoes when compared to some of the more economically or medically important mosquito species that have been better studied. Aedes pullatus are among the least studied mosquitoes, not currently known to vector any human diseases, and only a biting nuisance locally. If you happen to be in the right mountain forest, at the right time of year, you may encounter large numbers of these blood-hungry female mosquitoes, but otherwise they go about their lives unnoticed by most people.

Perhaps future researchers studying cryogenics or cold-tolerance in animals would find these mosquitoes to be fascinating organisms to work with, but otherwise they are not likely to attract much attention. At least for this mosquito researcher, whenever I have the opportunity to visit the mountains in the springtime, I will continue to peek under the ice and marvel at these cold-adapted insects.

Contact Us to Learn More About Effective Mosquito Management Strategies:

VDCI_Logo_squareSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.

Sabethes cyaneus – the Paddle-legged Beauty

Exploring Unique Mosquito Species

Valentine’s season is upon us — whether we like it or not, our obsession with courtship seems to take center stage. Indoor creatures, like humans, are not deterred by the winter; but, for most insects in the Northern Hemisphere, it is still too cold outside for mating. Meanwhile, in the tropics, many species are active throughout the year. Outside of a geeky entomology laboratory, it is quite rare for a discussion about courtship to include any mention of mosquitoes; the vast majority of species don’t display any behavioral patterns complex enough to even qualify for the term. For most mosquitoes, mating is a fast and haphazard occurrence with swarms of males circling around and waiting for the sound of female wing-beats. Once detected, the male rushes after the female and immediately attempts copulation mid-air without so much as a “how do you do?” – this is not courtship.

There is one notable exception, the paddle-legged beauty, Sabethes cyaneus. This tropical forest species lay their eggs in shaded natural and artificial containers such as tree-holes, bamboo hollows, and even fallen banana leaves filled with rainwater. Sabethes larvae develop in these small source pools and feed on bacteria, algae, and other organic material. The beautiful adult Sabethes mosquitoes are usually encountered in close proximity to the small habitats of their youth.

Few people would use the words “beautiful” and “mosquito” in the same sentence, but Sabethes cyaneus has few rivals when it comes to looks. Its color is predominantly a stunning iridescent blue, marked with contrasting silvery-white spots – especially, on the abdomen (Wow!). Bold colors are not their only unique feature; the feather-like paddles catch the eye as well. Formed by elongated scales, located on the tibia of each middle leg, both the male and female sport these strange paddles. The function of the paddles is not fully understood; however, in the late 1980s, Dr. Robert Hancock and his colleagues observed mating behaviors that may lead to a better understanding.

WARNING: The following paragraphs contain graphic descriptions of mosquito courtship behavior – parental discretion is advised.

Dr. Hancock’s team described the unique and elaborate series of stereotypical behaviors displayed by Sabethes mosquitoes prior to and during mating. Although dinner and dancing is not required as part of the ritual, the males must go through a number of displays and movements, in a specific order, and the female has multiple opportunities to accept or reject his advances.

The wooing begins with the female resting on the underside of a horizontal surface, such as a stick or twig. The male, apparently attracted by her stunning beauty, hovers around the female with his leg paddles outstretched. He then places one of these middle legs (midlegs) over her wing, perhaps preventing her from just flying away, but also to be used as a pivot point as he swings around to face his date and simultaneously grasps the twig with his front legs. Once aligned, the true courtship begins. The male waves his free midleg back and forth, apparently showing off his lovely paddle, but eliciting no apparent response from the female. Next, the male will flex his forelegs to create a bout of rhythmic body “swinging” while simultaneously flicking his proboscis (tube-like mouthpart) downward. If successful, this display will induce the female to lower her abdomen sufficiently for copulation to take place. If unsuccessful, he would return to waving his free midleg, followed by another round of rhythmic body swinging, until she either lowers her abdomen or uses her hind legs to reject him by pushing him away. During copulation, the male gyrates his abdomen while waving his middle and hind legs alternately until mating is completed and the pair disengages (Whew!). Lots of effort, compared to other mosquito species and most other animals.

So, in regards to mating, how important are those feather-like paddles? Hancock and his colleagues did some experiments to find out, removing the paddles and observing the results. If removed from the female, the males rarely approached. Apparently, for females, the paddles serve to attract the males. However, if the paddles were removed from the male legs, the males approached females to court with the same levels of success. What specific functions these paddles serve on the males remains unknown.

The snow is falling outside my window, as I write this, making me wish that I was in the tropical habitat of the Sabethes cyaneus. Then, I could observe this beautiful mosquito and its unusual courtship behaviors first-hand. For most of the over 3,000 species of mosquitoes identified, hardly anything is known about their biology and behavior. Perhaps there are other unusual stories of mosquito courtship waiting to be discovered in a tropical forest.

An important component of any successful Integrated Mosquito Management program is mosquito identification. Should you have any questions regarding mosquito identification, Vector Disease Control International (VDCI) is always available at whatever level of assistance you desire.

Contact Us to Learn More About Effective Mosquito Management Strategies:

VDCI_Logo_squareSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.

Mosquito of the Month: Aedes albopictus – the Asian Tiger Mosquito

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Deep Dive Into the Asian Tiger Mosquito

As if we didn’t have enough mosquitoes in the USA to deal with already, someone had to go and import one from across the ocean.  Great – thanks a lot!  

Nobody is really sure exactly when the first of these invaders arrived into the USA , but the original recognized North American specimen of the Asian Tiger Mosquito, Aedes albopictus, was collected in June 1983 from a cemetery in Memphis, Tennessee. The species has since become one of the most challenging mosquitoes to control, and brings with it a host of other disease-related challenges.   

So what makes this invader such a challenge for mosquito control programs? While most mosquitoes are vampire-like in their avoidance of the sun, waiting until after sunset to seek a blood meal, the Asian Tiger Mosquito can more likely be found actively biting during the daytime in full sunlight. That’s not good. Most modern adult mosquito control occurs after sunset in order to avoid negatively impacting day-flying insects like bees, butterflies, and other popular pollinators. Any pesticides sprayed at night are dissipated by the time the Asian Tiger Mosquitoes take to the wing the next day.   

The larvae are equally evasive to typical control programs that are focused on treating larger swamps, ponds, and marshes where most native mosquito larvae thrive. However, the Asian Tiger Mosquito is a “container breeder,” meaning that, like the Northern House Mosquito featured in our December 2015 Mosquito of the Month posting, the larvae thrive in small containers of water. In their native habitats, they lay their eggs in tree holes, rock pools, and even coconut shells, but they’ve adapted to manmade containers as well – any small items that hold water for a long enough time for the larvae to develop.   

Imported tires are the likely source of the original invaders into the USA. For example, the first established population was recorded in Texas in 1982, and used tires were identified as their primary larval habitat there. In 2003, the first record of the species in Colorado was from a trap less than 1/10 mile from a tire storage site. Unlike the Texas populations, they didn’t establish in Colorado, probably due to the dry conditions reducing the number of available water-filled containers for egg-laying and larval development. The same is true for the arid regions around Los Angeles, California, where they are believed to have arrived multiple times in oceanic container shipments of cargo such as “lucky bamboo” plants (Dracena spp. – neither lucky nor bamboo), but still have not established large populations. Unfortunately, in more humid environments such as in eastern USA, the Asian Tiger Mosquito has become successfully established, especially in warmer states like Florida. The key to this mosquito’s international spread and successful introduction has been primarily due to the fact that used tires are an ideal place for the larvae to survive, and millions of tires are imported each year into the USA, and travel between states regularly.  

The species was first described in 1894 by F.A. A. Skuse, a young British Entomologist working at the Australian Museum in Sydney, who received specimens from Calcutta where the insect was reported to be “a great nuisance.” Skuse gave his “banded mosquito of Bengal” the Latin species name “albopictus,” meaning “painted white.” As mosquitoes go, the Asian Tiger Mosquito is certainly one of the most gorgeous to look at under a microscope. A velvety jet-black background is marked with contrasting bright, silvery-white patches of scales on the legs, thorax, and abdomen, making this species stand out from the rest when looking at a pile of collected mosquitoes. Especially stunning is the white “racing stripe” that extends from the front of the head, all the way down the back of the thorax to the area between the base of the wings. Wow. She’s a beauty, but she packs a potentially deadly punch.

Beyond being a daytime biting nuisance, the Asian Tiger Mosquito is also capable of transmitting several diseases, including dengue, West Nile virus, chikungunya, and several forms of encephalitis. The presence of this invasive species has become a major public health concern in many locations across the country, especially in the southeastern states.

As humans can now cross the great oceans in hours instead of weeks, the introduction of exotic insects has become a huge concern, and this mosquito is a fine example of why it is important to prevent stowaways from hitching along when we travel around the globe. It is too late to stop this species from invading the USA, and it is likely here to stay, but we can at least keep their numbers in check to reduce their negative impacts. If you live in a part of the country where the Asian Tigers are common, you can do a lot to help reduce their population by inspecting your yard for pools of standing water, no matter how small. Don’t forget to check your rain gutters for clogs that hold water, and even gardening equipment or children’s toys. Eliminating their backyard larval habitats is the key to keeping these invaders under control. Learn more in our source reduction blog.

An important component of any successful Integrated Mosquito Management program is mosquito identification. Should you have any questions regarding mosquito identification, Vector Disease Control International (VDCI) is always available at whatever level of assistance you desire.

Contact Us to Learn More About Effective Mosquito Management Strategies:

VDCI_Logo_squareSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.

Mosquito of the Month: Culex pipiens – Northern House Mosquito

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Exploring The Culex Pipiens Species

It is winter and all the mosquitoes have died, right? Well, not exactly.  

While many species of mosquitoes laid eggs last summer or fall and then died, others including the Northern House Mosquito, Culex pipiens, overwinter as an adult, waiting until next spring to lay their eggs. Throughout temperate zones of North America, Europe, and Asia, there may be snow on the ground outside, but these mosquitoes can still be found if one knows where to look for them. 

In late summer and early autumn, these mosquitoes forego the blood meals and instead fuel up on nectar or other sugary fluids, storing it as fat in their body. Before human construction, they likely spent the winter in caves or hollow trees – protected from the worst of the winter elements. In such shelters they remain warm enough to keep from freezing to death, but cool enough that they don’t burn up all of their fat reserves before spring. Humans have provided them with additional safe winter hiding places, including culverts, barns, stables, garages, basements, and sheds. Some populations have even developed the ability to be active year-round in warmer structures such as the London Underground railway system, where they were notorious for attacking the city’s citizens who were seeking shelter in the subway tunnels during bombing air-raids of World War II. If you find a mosquito flying around your garage on a warmer-than-normal December day, or resting on the wall of your shed in the middle of winter, it is likely this species.  

As mosquitoes go, the Northern House Mosquito isn’t the most spectacularly colorful or patterned, although in the right light their golden brown body scales have a somewhat bronzy reflection. Their abdomen is distinctly marked with pale-colored scales that form broad rounded banding on each segment. I’ve seen prettier insects, to be sure, but few with such a vast global distribution, found on every continent except Antarctica.  

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In the past, they were sometimes known as the “rain barrel mosquito” as they took advantage of that once commonly available water source as a place to lay their eggs.  Culex pipiens larvae thrive in such containers of stagnant water, the more polluted with organic material, the better.  If you live in the northern half of the United States and have mosquito larvae in your bird bath, rain gutters, flower pots, or nearby storm drain catch basin, it is likely to be this species. 

Adult females will sometimes enter buildings where they readily bite humans, but outdoors they apparently have a preference for bird blood, especially birds associated with human dwellings such as pigeons and doves.  They are competent vectors of West Nile virus, a disease mostly found in birds.  This mosquito has been implicated as a primary vector that amplifies the virus each summer in the previously unexposed bird population (the disease’s “reservoir”).

In much of the country, Culex pipiens populations are the primary target of the campaign to drain backyard sources of standing water as a way to reduce the incidence of West Nile virus.  Next summer, check to see that your rain gutters are flowing, and flush your bird bath every week.  You just might notice a decrease in the number of mosquitoes in your yard, and will help reduce the West Nile virus risk in your neighborhood.  

An important component of any successful Integrated Mosquito Management program is mosquito identification. Should you have any questions regarding mosquito identification, Vector Disease Control International (VDCI) is always available at whatever level of assistance you desire.

Contact Us to Learn More About Effective Mosquito Management Strategies:

VDCI_Logo_squareSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.

Mosquito of The Month Series, General Overview

Exploring Mosquito Species: Where They Live and Breed

“Seriously?  You get paid to identify mosquitoes?  How many kinds of mosquitoes are there?” 

Years ago when I started working in a mosquito control surveillance laboratory, some of my non-scientific relatives and friends were surprised to hear that there were so many different species of mosquitoes, and that there was a need to tell one kind of mosquito from another.  In fact, according to the Walter Reed Biosystematics Unit/Smithsonian Institution, there are nearly 3,300 named mosquito species currently recognized worldwide.  In the United States alone, more than 175 species have been recorded. 

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 With so many species of mosquitoes discovered so far, it would take almost 275 years to run out of species to write about for a Mosquito of the Month blog posting.  However, for many mosquitoes, we only have a name, physical description, and location where they have been discovered – little or nothing is known about their biology, natural history, and behavior.  A relatively few species have been studied in more detail, yet for those species that we do know more about, mosquitoes turn out to be a highly diverse and fascinating group.  

Just as with butterflies, adult mosquito bodies and wings are covered with tiny scales that together create a variety of species-specific patterns.  While most species have scales that are black, gray, brown, and white, there are some primarily tropical species that display iridescent blue, purple, green, silver and gold colors as well, rivaling the butterflies for beauty, albeit at a more microscopic level.  These patterns, along with the placement, presence, or absence of various sets of hairs and spines, are primarily what entomologists use to distinguish one species of mosquito from another. 

So why is identifying the species an important component of mosquito control?  Mosquitoes vary greatly in the preferred habitat they live in as larvae, and it is usually more efficient to control larval mosquitoes in the water before they become blood-sucking winged adults.  By identifying the mosquitoes that we trap, we can use what we know about their preferred habitat to find where they lived as larvae and prevent others from developing.  Also, not all mosquitoes are efficient vectors of diseases, so by looking at the prevalence of disease carriers in our traps, we can predict the potential severity of outbreaks, or take increased measures to reduce or prevent disease transmission.  

It wasn’t until the late 19th century that researchers like Carlos Finlay, Walter Reed, and others demonstrated the connection between mosquitoes and diseases like Yellow Fever and Malaria.  Prior to that time, mosquitoes with exotic-sounding scientific names like Aedes aegypti and Anopheles gambiae were just seen as a nuisance, of little importance to science.  Today we know that these insects are responsible for more human deaths annually than any other animals except perhaps humans themselves.  In many wars prior to that discovery, more soldiers died from mosquito-borne diseases than from bullets.

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Each month we will take a closer look at a different mosquito species, with the intention to showcase this highly diverse group of insects.  We will examine various unique and interesting adaptations they use for survival, unusual behaviors, and even their historical importance.  We will look at species that are common, and some that are rare; species with global distributions, and others that are only found in isolated circumstances; mosquitoes that have had great impacts on human civilization, and others that go about their lives unnoticed by us for the most part.  We will discuss scientifically demonstrated facts and dispel some commonly held myths.  

An important component of any successful Integrated Mosquito Management program is mosquito identification. Should you have any questions regarding mosquito identification, Vector Disease Control International (VDCI) is always available at whatever level of assistance you desire.

Contact Us to Learn More About Effective Mosquito Management Strategies:

VDCI_Logo_squareSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.