Dealing with Mosquitoes

 Dealing with Mosquitoes 

Asian Tiger Mosquito Andes albopictus 
Source: Centers of Disease Control and Prevention (CDC)

Mosquitoes are a part of life in Southeastern North Carolina and they can be both a nuisance to people and a potential danger to birds. At the same time, most of our native mosquitoes are beneficial to the landscape as they provide food for predatory insects, spiders, and even birds, while some species pollenate flowers. In this week's article, I will discuss the ways that we can deal with mosquitoes without resorting to harmful pesticides. 

Mosquitoes

Mosquitoes (Family Culicidae) are small to mid-sized insects that belong to the insect order Diptera and are in the same group as houseflies, hoverflies, and midges. All of these insects have a single pair of wings and differ from flying insects like bees or wasps (which have two pairs of wings). There are hundreds of species of mosquitoes in North America although only a small handful bite people or pets. In the Cape Fear Region, the main nuisance mosquito is the Tiger or Day Mosquito Ades albopictus which is common in Wilmington from April to as late as December depending on how cold it gets. A few other nasty species include our native Culex mosquitoes (like the House Mosquito), Floodwater Mosquitoes (Andes vexans) and the giant Psorophora (commonly called Gallinippers) which mainly occur near wetlands or after major rain events like tropical cyclones. Outside of these examples, many species are relatively harmless and some do not bite people at all. Mosquitoes are not to be confused with the large but harmless craneflies, predatory robberflies, or swarms of midges as none of these bite people. 

Lifecycle 

Mosquitoes are fascinating species from an entomology standpoint and like butterflies they undergo metamorphosis. All mosquitoes require water to breed and complete their larval and pupal stages in bodies of stagnant water. Most of our native species breed only in puddles, vernal (temporary) ponds, tree holes, or in flooded meadows and rarely survive in water features with fish, or aquatic insects (dragonfly larvae, water scorpions etc). Because of this, most of the woodland and meadowland mosquito species only bother us when we are hiking, kayaking or happen to live next to such an environment. Species that breed in floodwaters or puddles may become abundant days or weeks after hurricanes or major rain events but are temporary issues. The only mosquito that is a major problem in our gardens is the Asian Tiger Mosquito which is a nonnative species introduced in imported tires and other objects that carry water. Most species complete their development in 1-2 weeks while the Tiger Mosquito can go from egg to adult in just 7 days.

Breeding Habitat: Most mosquitos choose marshes, stagnant ponds, or other wetlands for habitat and stick to natural areas. The Tiger Mosquito can breed in any body of water including rainwater that collects in flowerpots, clogged gutters, or rubbish left on roadsides. A bottle cap may provide enough water this species to breed, and forgotten flowerpots or old tires can become mosquito factories. In general, mosquitoes avoid moving water and environments with fish.

Range: Most mosquitoes travel only a few hundred meters from their breeding source and mostly bite victims within that radius. Saltmarsh Mosquitoes and Floodwater Mosquitoes can travel very long distances but are little more than nuisances and are most common after hurricanes. In most cases if you are being bitten by mosquitoes the source is not far away. 

Breeding: The breeding cycle of mosquitoes is similar to other insects. Mosquitoes protein to develop eggs which is why some species bite other animals. After mating, the eggs are laid on bodies of water or nearby vegetation and will hatch shortly after. The eggs may of some species  remain inactive for long periods of time until they come in contact with water. Larvae consume detritus and resemble small worms that have breathing siphons on their tails. After pupating, they emerge as adults and restart the cycle. 

Ecological Role: While mosquitoes are often viewed for their annoyance or health risks, they have a role in our ecosystems. Aside from being a food source, the insects pollenate certain plants just like other flies, while their larvae consume detritus in ponds. In turn, mosquitoes can also cause harm to birds and wildlife. Overabundance of biting midges, mosquitoes, and blackflies can kill or weaken bird nestlings, reptiles or amphibians, and increase stress in large animals like deer. They can also carry diseases and parasites that can impact local ecology. Over abundance of mosquitoes in your garden can be bad news for birds as many avian borne diseases can be transmitted through mosquitoes. 

Controlling Mosquitoes

Properly working fountains rarely harbor mosquitos 

Mosquitoes can quickly become an issue in a garden or public area if they are left unchecked. While their bites are annoying or painful, some species can be vectors of disease. The insects can also weaken livestock, and lead to other consequences as well. Cities, counties, farmers, and citizens take many measures to control mosquitoes although most solutions rarely solve the problems, and are at best a temporally solution. Certain actions can lead to unintended consequences such as the loss of other insect species such as native bees, dragonflies and domestic honeybees in area hives. On a community level, county or state agencies may spray communities for mosquitoes to control disease vectors or treat ditches, floodplains, and other wet areas with larvacides to inhibit breeding. New Hanover County (NHC) for example only sprays when a disease communicable to humans or livestocks is detected and a population threshold has been met (based on scent traps, wetland survey and other sampling means). While homeowners can buy mosquito foggers, persistent insecticides or pay for a commercial mosquito service, pesticide applications should only be a last resort. Such actions can cause risks to native insects, reptiles, birds, or people sensitive to certain chemicals if done incorrectly or too often. Below are some measures to reduce or even get ride of mosquitoes in you garden without chemicals. All of these measures are simple tasks that can make a big difference for your family and your neighbors.  

Tip and Toss: The best way to control mosquitoes in your garden is to dump standing water and remove or cover anything that can hold water. Flowerpots, clay saucers, plastic tubs, and old tires are just some of the items that can harbor Tiger or Floodwater Mosquitoes. An object as small as a bottle cap can be enough for mosquitoes. Trash such as snack wrappers, cans, beer cans, or abandoned appliances may also host mosquitoes and should be cleaned up. According to NHC, most mosquitoes have a limited range and eliminating sources will reduce encounters with these insects. 

Clean Birdbaths: Birdbaths and other water features should be dumped out and refreshed daily and cleaned once a week. 

Moving Water: Larger water features such as fountains, garden ponds, and container marshes should be aerated with pumps or another device that keeps the water moving. Alternately you can stock garden ponds with fish to keep mosquitoes at bay. 

Organic/Home Remedies: Add organic or biological larvacides into containers of water you intend to keep or cannot easily tip or dump. These products are available in most hardware stores, and your county or town may even offer them for free at the government center. Mosquito control sticks often look like doughnuts and last for weeks or months at a time. You could also use dish soap, Castile soap, or another nontoxic (preferably organic) substance that makes it harder for mosquitoes to lay  eggs or prevents the larvae from breathing (if the container is not also being used by frogs or other animals). 

Cover Rain Barrels: Cover all rain barrels with screen or mesh small enough to keep mosquitoes from getting in. A Tiger Mosquito is 0.3cm (1/8th of an inch) and can get through some types of mesh. Keep the barrel from overflowing as well.

Natural Predators: Another solution for mosquitoes is to provide habitat for natural predators. Dragonflies, damselflies, lacewings, robberflies, certain wasps, and web-spinning spiders readily eat mosquitoes. Certain birds and reptiles may also eat mosquitoes in small numbers. In the water, dragonfly larvae, minnows, frog tadpoles, water scorpions, and  aquatic beetles eat mosquito larvae. Destroying wetlands to combat mosquitoes will only reduce the natural predators, and will not control nonnative mosquitoes as they can breed anywhere

Avoiding Mosquitoes   

It is best to hike near wetland forests during the midmorning 

The best way to minimize the risk of being bitten by mosquitoes or other biting flies is to avoid them in the first place. Most of our native species are active during a small window between dawn or dusk, or on overcast days. Avoid hiking in forests or marshes or wear protective clothing (long trousers, shirt, face netting if you have it) during peak times. The Tiger Mosquito, is mostly active during the daytime but stick to forests, shady areas, and areas with dense vegetation. Still these insects will be less active during the heat of the day or in open areas away from woods or brush. 

• Hike, walk, or exercise during the day as mosquitoes are most active at dawn and dusk

• Mosquitoes are more numerous in damp forests, wetlands, and other shaded habitats.

• Wearing long trousers, long sleeve shirts, and closed shoes will protect you from most mosquitoes (including Tiger Mosquitos), you could also use a face net. 

• Mosquitoes are less common from late October to early April in the Carolinas, and seem to peak around July, August, or September. 

• Mow grass and reduce dense undergrowth near the home to keep mosquitoes further away from doorways or outdoor areas. Invasive plant infestations (privet, wisteria, kudzu) provide lots of cover for mosquitoes but not native predator.

• Use a handheld bug zapper to kill biting insects around you without chemicals, be advised that wands can generate a shock if touched so do not touch the grid when the light is on.

• Use approved repellents, or home remedies such as Clove Oil or herbal solutions to repel mosquitoes or deal with bites. Please read the instructions, and seek appropriate medical advice before using any repellent or home remedy as some things can cause allergic reactions. 

Cicadas

 Cicadas

Also check out the previous articles about frogs and butterflies. 

A close-up of a Dogday Cicada 

When the choruses of birds start to wane in the late spring, and frogs finish their courtship cycles, the forests and woodlands become quieter. By midsummer, the forests are alive with sound again, this time from singing insects. Crickets, katydids, and cicadas are among our most talented singers and their voices will take the place of songbirds from June onwards. Katydids and crickets sing at all times of day although the best song choruses take place from dusk to dawn. Cicadas are diurnal singers that can be heard at sunrise, during the heat of the day, and just before nightfall. Of the singing insects in the Carolinas, cicadas are among the most familiar and certainly the loudest of the bunch. Aside from their loud whining songs, the average person or even many nature lovers have very little understanding of these wonderful creatures. 

What is a Cicada

Cicadas are insects in the order Homoptera that are in the same grouping as true bugs, aphids, and  scale insects. These insects are rather long-lived with some insects having lifecycles that last more than 10 years. Like with butterflies, we are most familiar with the adult stage which typically lasts around a month. Adult cicadas are rather large insects  with hard exoskeletons, large wings, and eyes. They look like a creature from another world and their large size, and loud flight can be alarming to some people. However, cicadas are completely harmless and can be told from wasp species such as Bald Faced or Giant Hornets by their robust bodies, heads, and legs. Many cicadas have vivid color patterns and can be green or brown with an array of patterns and markings. There are seven species of cicadas known in the Carolinas with six of them being "annual cicadas" and the last one being the Linnaeus's 17-year Cicada. All species develop amongst tree roots and emerge from the ground after competing the nymph stage. In our area, Cicadas are active from late spring (around May 12th-13th in Wilmington) to early autumn (as late as October 20th) although the peak season is between the final weeks of July and mid-September. 

Lifecycle

Cicadas are are an example of a long-lived insect that can live anywhere from several years to nearly two decades. Other examples of long lived insects include some aquatic species, and a species of moth in the Arctic that needs several short summer cycles to emerge. Like the other insects, most of a cicada's lifetime is spent in the nymph stage where they feed on plant roots, grow, and molt. Once they complete their final molt, the nymphs will emerge from the ground and climb up tree trunks or a wall to harden. After that the insect leaves its former exoskeleton behind and is ready to fly. Adults live several weeks to a month and feed on plant juices using their piercing mouthparts. Male cicadas sing to attract potential mates. After that, the females lay eggs in tree branches or twigs and the cycle begins again. 

Annual or Periodical

There are two "types" of cicadas. The ones that most people are familiar with are the periodical cicadas which emerge in large numbers specific cycles. These cicadas can live as long as 17 years and have synchronized breeding cycles. During brood years, these insects emerge by the millions and can create a deafening roar from late spring to early summer. Many people assume that all cicadas emerge every 10-20 years and the insects heard each summer are different generations. In reality, the true Periodical Cicadas are only seen in specific years, in the Carolinas, every 13 or 17 years. Periodical Cicadas are part of the family Magicicada and are most prolific in the Appalachian Corridor and Interior East.  

The second and most commonly encountered cicada are the annual cicadas. These cicadas complete 1-2 year lifecycles and emerge every year. While some years may bring greater numbers of cicadas than others, you will see most of the species in our area annually. We have six or seven species of annual cicadas in the Cape Fear Region with all of them being numerous from June to September. Some species of cicadas such as Hieroglyphic Cicadas emerge early in the season and persist to autumn, while others like the Dogday, Dusk-Singing, and Scissor-Grinder Cicadas emerge later in the summer.  

Songs 

Adult cicadas sing loud whining or buzzy songs from late spring to autumn to attract potential mates. Each species of cicada has its own song and like birds and frogs, one could learn the differences between the songs with enough skill and passion. No other creature in our area produces the same type of noise as cicadas. They are also among the loudest animals in the Carolinas with a full chorus of annual cicadas being loud enough to drown out conversation or get one's attention in a park or woodland. However, the swarms of Periodical Cicadas are truly a sight and sound to behold, and the noise alone is deafening. Most species also have a flight call (usually a chirp or buzz). Cicadas differ from crickets and katydids in a number of ways. All species are diurnal singers meaning they only sing during the daytime hours (though many species sing at daybreak and nightfall). Katydids and crickets can be heard day or night but are most active after sunset, while many species are strictly nocturnal. The second difference is the sound itself. Cicadas produce a droning or staccato whine, buzz, or whirl (like a mechanical device or certain fire alarms), while katydids and crickets produce high pitched chirps, trills, and buzzes (some like an hum of an electrical arc or the click of a lawn sprinkler). Lastly, grasshoppers, crickets, and katydids produce noise with their legs, while  cicadas have special organs in their abdomens for sound. 

Ecological Role

                Cicada Habitats: Appalachian Hardwood Forest (left) Turkey Oaks and Pines (right)

Cicadas are an important part of the forest ecosystem and are a valuable food source and generate biomass in woodlands. All cicada species depend upon hardwood or certain coniferous trees for reproduction and their presence indicates a healthier forest or urban tree canopy. While there is the suspicion that cicadas can girdle forest or orchard trees, or damage wood products, they do not cause that much damage to trees. Nonnative bark and wood beetles such as the Asian Longhorn Beetle, and an introduced Pine Beetle are the real threats to forests, while other stressors such as drought, soil compaction, and deforestation pose greater harm to forests and cultivated trees than cicadas. Cicadas do not eat or bore into wood so they are no threat to human structures. As stated above, cicadas pose no danger to humans and are actually fascinating creatures. Population booms of annual cicadas or the emergence of periodical cicadas can lead to increases in songbird populations. 

Predators: Cicadas are eaten by a wide variety of animals although birds and mammals are the main predators. Adults are an easy food source for mid-sized and large birds such as Crested  Flycatchers, jays, tanagers, cuckoos, crows, ravens, and kites. Red Shouldered and Broad Winged Hawks as well as Kestrels will also prey on cicadas when they are around. Grey, Red, and Fox Squirrels, ground squirrels  weasels, bats, and certain mice or rats are just some of the mammals that will supplement their diets with cicadas. Probably the most interesting cicada hunter is a large but docile wasp known as the Cicada Killer Sphecius speciosus which is is common in our area from late May to September. These wasps look like Giant Hornets, are loud, and can be intimidating when they burrow into lawns or fly overhead. However, these wasps (like most of our solitary species) pose little harm to us, and are not only strong predators that can take down cicadas but are important pollinators.  Other kinds of wasps may also take down cicadas, as well as several robberfly species, dragonflies, and large orbweb spiders. The fascinating and completely harmless Ichneumon Wasps may also lay eggs on cicada nymphs by probing their ovipositors into the ground, although most species prey on horntails or wood beetles.

Detritus: Dead cicadas are a major source of biomass in forests and woodlands. After a cicada finishes its lifecycle and mates, the insect dies. The remains provide ample food for ants, isopods, earwigs, and other scavengers, while birds, squirrels and skinks may clean up recently deceased or dying cicadas. The ones that are not eaten will decompose and become part of the soil. Periodical cicadas emerge in such large numbers that the understory can be covered in dead insects after mating has concluded. 

Cicada Predators

Cicada Killer wasp with prey

Acadian Flycatcher

Golden Silk Weaver Spider

Cicada Species (Listen to examples at Song of Insects)

Hieroglyphic Cicada Neocicada hireoglyphica: The Hieroglyphic Cicada is our earliest annual cicada species to emerge and is often heard in the first or second week of May. This cicada persists through the summer and into autumn, indicating there may be several broods. The cicada itself is somewhat distinctive as its all green or turquoise with a yellow body, and is rather small. They live in treetops and are found in all types of woodlands including parks and neighborhoods. The song consists of several pulsing buzzes before it becomes steady for several seconds before tapering off. The pulsing sounds are comparable to a small electric motor revving up. Song Example

Swamp Cicada Tibicen chloromera: The Swamp Cicada id a dark colored cicada that is mostly found near wetlands, edges of meadows, and shrublands. They are among the few examples of Cicadas that live near the ground and are probably the species responsible for the exoskeletons found on sheds, fences, and plant stalks. They emerge in early summer and produce a pulsating buzz that lasts for up to 15 seconds. This cicada has a rather choppy song and is best compared to miniature compressor motor. Song Example

Linne's Cicada Tibicen linnei: The Linne's Cicada is another common species that is similar to the Swamp Cicada except greener and has clear wings. This species is found in deciduous or mixed forests, wood habitats, and in gardens from midsummer to autumn. Its shells can be found on buildings or walls like the Swamp Cicada. This species sings just before dusk. The song is comparable to a shaker and rises in volume before ending abruptly. Song Example

Scissor Grinder Cicada Tibicen pruinosa: The Scissor Grinder Cicada is a widespread species of Cicada that occurs across much of the Eastern and Midwestern United States and is likely present in our area as insect range maps are depended on collected samples. This cicada is rather large and is similar to the Linne's Cicada above. It lives in various woodland habitats or in gardens. Its song is an unmistakable chirping series that sounds like "Churrip-Churrip-Churrip" and lasts for up to 20 seconds. This song is heard from early July into September and can be heard in the heat of the day or at nightfall. Song Example

Dusk Singing Cicada Tibicen auletes: The Dusk Singing Cicada is a large cicada that is almost 5cm or 3" long and is one of the largest species in our area. This cicada emerges in mid to late summer and is one of the last species that can still be heard in the autumn. They  are found in a variety of Eastern Forests as well as in parks, gardens, and woodlots. They mostly sing just before nightfall and make a loud alarm call when chased by birds or startled. The song is a long rising series of buzzes that begins as a "dee dee deee deeee deeeeee deeeeee" before the buzz becomes continuous before fading out. It is low pitched and can sound like an aircraft getting a radar lock on a target (accelerating beep until a continuous tone). Song Example   

Dogday (Davis's) Cicada Tibicen canicularis: The Dogday Cicada is a fairly small  cicada that emerges from June and remains active well into September. These cicadas are aptly named for their tendency to sing during the heat of the day (along with the Swamp, Scissor Grinder, and Hieroglyphic Cicadas. It occurs in various types of forest but is particularly common around pines and oaks. This cicada produces a short but loud song that sounds like a power saw cutting wood. Large numbers of these cicadas can be quite overpowering. Song Example 

Lyric Cicada Tibicen lyricen: Lyric Cicadas are a mid to late season cicada that often comes out in July or August and is among the last species to remain active after Mid-September. This cicada is rather large and has a reddish or mahogany brown markings on its thorax. This cicada is found in various woodlands including parks and sings from sunrise to sunset with peak choruses occurring just before nightfall. This cicada produces a continuous trill that lasts for almost a minute and has no pulsing or chirping pattern. It can be mistaken for some katydids but the sheer volume of choruses is unmistakable. Song Example 

Linnaeus's Cicada Magicicada seeptendecim: The Linnaeus Cicada is one of the multiple species of periodical cicadas that occur in Eastern North America and the best studied of the group. This cicada is known as the 17-year cicada or locust because broods take 17 years to mature. Since this species has a synchronous breeding pattern, all members of a given population (usually within a local woodland or forest tract) will emerge and breed at once. This leads to thousands if not millions of insects being active over a 2-3 week period before the cycle restarts. Periodical cicada cycles bring an abundance of food for birds, predatory insects, and rodents, and rejuvenate forests when all of the adults die off and add to the biomass. These kinds of cicadas are sensitive to habitat loss and deforestation, logging, and use of insecticides can wipe out nymphs or adults, leading to local extinctions. It is not clear if we have we periodical cicada species in the Cape Fear Region, although the book I am using as a source Songs of Insects by Lang Elliot does place the Linnaeus Cicada in the Carolinas. More insect surveys are needed to improve range maps or separate similar species. This specie's song is a hollow whine that can be compared to a jetliner taxiing in the distance, or in nature, a chorus of Southern Toads. If you visit a forest during a brood year, the sound is unforgettable and is so loud that you can barely hear anything else. Song Example

Sources

1. The Song of Insects, Lang Elliot and Wil Hershberger, 2006, NatureSound Studio, New York Yew York.