Wyeomyia smithii

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Geographic Range

The purple pitcher-plant mosquito, Wyeomyia smithii, is found in the Nearctic Region from the northeastern coast of the Gulf of Mexico to northeastern Saskatchewan. The distribution is determined by the range of the purple pitcher plant, which is found from 30° N to 50° N in North America. (Lounibos, et al., 1982)

Habitat

This species' larval stages live submerged in the aqueous reservoirs (inquiline habitat) of their hosts, the purple pitcher plants. Airborne adults may travel, but generally remain near the plants where they hatched. Purple pitcher plants are found in wet areas in North American forests, usually in clusters near streams. Although normally found in moist climates, they are sometimes found in grassland areas. (Bradshaw, 1980; Hard, et al., 1993; Lounibos, et al., 1982; Rook, 2004)

Physical Description

In its larval stages Wyeomyia smithii is extremely small with white or clear skin. This insect has only two anal gills, compared to other Wyeomyia that normally have four. Depending on the larval stage, Wyeomyia smithii can weigh anywhere from .4 mg to 2.5 mg upon eclosion, or the shedding of pupal casing by a new adult.

The adult forms are dark brown to black and are approximately two centimeters in length with a wingspan of similar size. They have six legs and a pair of wings attached to the thorax. Adults rest with their legs bend forward, above their heads.

More research is needed on the other sensory organs of this species, however other mosquitoes develop several stages of eyes. Initial larval forms possess only a pit-eye ocellus, or simple eye, and more eyes develop as the larvae grow. The compound eyes of the adults are large and hexagonal.

This species is sexually dimorphic. Males undergo their final metamorphosis about two days earlier than females. Because of this extra time developing, females tend to be larger. Males also undergo a predictable rotation of their terminalia, the terminal grouping of body segments, that females do not. Males have two highly segmented antennae that are used to detect the vibrations of females' wings. (Crans, 2010; Harzch and Hafner, 2006; Mahmood and Crans, 1998)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range mass
    .0004 to .0025 g
    0.00 to 0.00 oz
  • Average mass
    .0015 g
    0.00 oz

Development

Wyeomyia smithii eggs hatch within the leafy pool communities of the purple pitcher plant and hatch most quickly after periods of dryness or freezing. In captivity eggs hatch within five days of oviposition. The larval form undergoes five instar stages over the course of about 22 days. Females remain in the fifth instar stage for an average of 2.1 days longer than the males as they develop ova and build fat stores. The instars of males are determined by the rotation of their terminalia (caudal segments). Males experience the final rotation between 9 and 12 hours after eclosion (hatching). Completion of this rotation is critical for successful copulation. Females emerge sexually mature.

The purple pitcher plant mosquito undergoes larval diapause depending on seasonal day length or moisture levels. This species uses the length of daylight, or photoperiodism, to determine the optimal time to enter hibernal diapause. Hibernal diapause occurs yearly in northern populations where their aqueous habitat freezes. All populations undergo diapause when water is removed from their environment. The effects of diapause were shown to significantly decrease the fitness of individuals by as much as sixty percent. (Bradshaw, 1980; Bradshaw, 1986; Bradshaw, et al., 1998; Mahmood and Crans, 1998)

Reproduction

Wyeomyia smithii are polygynous. Males deposit sperm into the spermathecae of multiple females if able. Males of similar mosquito species can identify and locate females by using their antennae to detect the vibrations of the female's wings. After copulation, females store sperm in their spermathecae to be utilized upon ovulation, which begins on average on day 24 of the females' life, or shortly after emerging from the pupal casing. (Bradshaw, 1980; Bradshaw, 1986; Bradshaw, 1980; Bradshaw, 1986; Bradshaw, et al., 1997; Bradshaw, et al., 1998; Harzch and Hafner, 2006; Mahmood and Crans, 1998)

Wyeomyia smithii eggs hatch during two seasons, late spring and early fall. This species exhibits protandry--males will develop an average of 2.1 (20 days old) days before females (22.1 days old). Male reproductive organs are found on the last segments of the body (terminalia) and undergo a 180° rotation from birth to reproductive maturity. Females emerge from their pupal shells sexually mature and are generally fertilized within two days.

The first oviposition of female is autogenous, meaning the species does not require a blood meal to deposit eggs. Northern populations are non-biting and thus obligatorily autogenous. Southern populations, however, are facultatively autogenous. After their first oviposition, females may consume blood to be able to lay more eggs.

There has been difficulty categorizing the oviposition patterns exhibited by W. smithii. Although W. smithii oviposits only a few times and dies before the next breeding season, females do not die after oviposition and are therefore not truly semelparous; many populations may lay several clutches within a breeding season and are therefore described as quasi-iteroparous.

Wyeomyia smithii are polygynous. Females store the sperm of males within their spermathecae which can be used for fertilization of multiple clutches. Females lay an average of 38 eggs per season with an average number of two clutches. (Bradshaw, 1986; Bradshaw, et al., 1998; Bradshaw, et al., 2003; Crans, 2010; Lounibos, et al., 1982; Mahmood and Crans, 1998; Moer and Istock, 1980)

  • Breeding interval
    Male purple pitcher plant mosquitoes will breed as frequently per season as possible. Females will only successfully breed with one mate as only one is required to full the spermathecae.
  • Breeding season
    Purple pitcher plant mosquitoes breed twice yearly, in the late spring and early fall.
  • Range eggs per season
    1 to 66
  • Average eggs per season
    38
  • Range gestation period
    1 to 8 days
  • Average gestation period
    2 days
  • Range time to independence
    0 to 0 minutes
  • Range age at sexual or reproductive maturity (female)
    20 to 25 days
  • Average age at sexual or reproductive maturity (female)
    22.1 days
  • Range age at sexual or reproductive maturity (male)
    19 to 25 days
  • Average age at sexual or reproductive maturity (male)
    20 days

Parental investment by females of this species is made largely during the fifth instar of larval development. Females remain in this instar on average two days longer than males while the unfertilized eggs develop. After completing metamorphosis and the subsequent copulation, females utilize sperm from their spermathecae to fertilize the eggs and deposit them within the pools of young purple pitcher plant leaves. After the first oviposition, southern populations may seek blood meals to produce more clutches. Northern populations do not seek blood meals and often do not lay more than one set of eggs. After deposition there is no known parental care. (Bradshaw, 1986; Bradshaw, et al., 1997; Lounibos, et al., 1982; Moer and Istock, 1980)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

After hatching, Wyeomyia smithii develop for approximately 22 days prior to eclosion depending on resource availability and sex. Since individual wild mosquitoes are difficult to track, determining the average age of wild mosquitoes is impractical. Captive individuals are usually reared in environments to mimic natural conditions and live an average of 38-42 days. (Bradshaw, 1980; Bradshaw, et al., 1998; Mahmood and Crans, 1998)

  • Range lifespan
    Status: wild
    Unknown to Unknown hours
  • Average lifespan
    Status: wild
    Unknown hours
  • Range lifespan
    Status: captivity
    Unknown to Unknown days
  • Average lifespan
    Status: captivity
    Unknown days
  • Typical lifespan
    Status: wild
    34 to 50 days
  • Average lifespan
    Status: wild
    38-42 days
  • Typical lifespan
    Status: captivity
    34 to 50 days
  • Average lifespan
    Status: captivity
    38-42 days

Behavior

This species is generally solitary although populations are usually concentrated around clusters of Sarracenia purpurea and may appear like swarms. There is no obvious coordination between individuals and they are not bound to stay within a group of individuals.

Like many mosquitoes, W. smithii stands in a manner known as sabathine, or with a pair of it's legs bent forward over its head. Females may maintain this pose while in flight, which is unusual since most other mosquitoes will bring the legs back while flying.

The adult form of this species is most active at dusk.

While all northern populations undergo a pupal hibernal diapause, members of this species may also undergo aestivation, or the diapause brought on in response to low water levels within their pools. (Bradshaw, 1980; Brown, et al., 1995; Hard, et al., 1993; Lounibos, et al., 1982)

  • Range territory size
    1 to 15 m^2
  • Average territory size
    5 m^2

Home Range

Individuals of this species tend to maintain a home range within fifteen meters of the plant where they emerged as larvae. (Bradshaw, 1980; Bradshaw, et al., 1998; Hard, et al., 1993; Mahmood and Crans, 1998)

Communication and Perception

Wyeomyia smithii is a model organism for photoperiodism and "hourglass" regulation studies. This species uses photoperiodism, the physiological regulation and reaction to changes in the length of day and night, as well as an internal clock to determine the time of year and development rate.

Northern populations rely heavily on photoperiodism as there are more drastic changes through the year in day length. Southern populations lose sensitivity to light as day lengths change less drastically so the larvae use an internal clock, often referred to as an hourglass in studies, to determine appropriate times for diapause and eclosion.

Adults also rely heavily on visual cues to determine prime locations for oviposition. Wyeomyia smithii will chose the youngest leaves. This is most likely due to nutrient availability as studies of the purple pitcher plant have shown that after 2-4 weeks, the capture rate of leaves drops exponentially. Selection may be signalled by the color of the leaves since other species of Wyeomyia prefer colors of younger leaves for oviposition.

While there is little research on W. smithii, mosquitoes in general find a mate based upon sounds produced by wing vibrations. The tactile receptors on male antennae detect the frequencies of female sounds, which helps species such as Aedes aegypti find mates. (Bradshaw, et al., 1997; Bradshaw, et al., 1998; Bradshaw, et al., 2003; Frank, 1986; Göpfert, et al., 1999; Rook, 2004; terHorst, 2010)

Food Habits

Wyeomyia smithii resides inside micro-communities in the phytotelmata (leaf contained pools) of the purple pitcher plant. Prior to eclosion, W. smithii feeds on bacteria, rotifers, protozoans, and midges as well as pieces of deteriorating insects caught by the pitcher plant's leaves. While it can eat these insect pieces, this species does not seek out insects and is not truly insectivorous. This mosquito is considered a detritovore and microbial filter feeder in its larval stages.

Adults, like with other mosquitoes, feed primarily on nectar and the fat stores from larval development. While they have can be sanguineous, this only happens after the first oviposition in southern populations and is generally considered rare. (Bradshaw, 1980; Bradshaw, et al., 1997; Bradshaw, et al., 1998; Crans, 2010; Hard, et al., 1993; Lounibos, et al., 1982)

  • Animal Foods
  • blood
  • body fluids
  • insects
  • Plant Foods
  • nectar

Predation

Wyeomyia smithi has no known predators of its own mainly because of its use of the purple pitcher plant. (Lounibos, et al., 1982)

Ecosystem Roles

The larval forms of this species live commensally within the phytotelma of the purple pitcher plant, Sarracenia purpurea. The commensalistic relationship benefits Wyeomyia smithii by providing a habitat for eggs and developing young, as well as a food source from the microbial populations and detritus it eats. The mosquito provides no direct measurable benefit to the plant, although this relationship is being continuously studied.

The larvae increase microbial biodiversity. Rotifer, midge, and colpodan abundances drop with the introduction of this predator, however bacterial abundance and richness increases greatly.

The direct predatory actions of Wyeomyia smithii impact the population size of its prey, and also play a key role in the evolution and population size of the ciliated protozoan Colpodea colpodida. Wyeomyia smithii will feed upon the colpopods, decreasing their population sizes. However, when populations of some other ciliated protozoans such as Pseudocrytolophosis alpestris are present, Wyeomyia smithii preferentially feed on P. alpestris since these are more free swimming. This preferential feeding indirectly affects the evolution of C. colpodida as it develops traits opposite to those expressed when W. smithii feeds only on these colpopods.

The purple pitcher plant mosquito can be considered a keystone predatory species since it impacts its community directly and indirectly at almost every level of the ecosystem. Wyeomyia smithii may reduce rotifer, midge, and colpodan populations, thus increasing bacterial diversity and abundance. This abundance may drastically increase decomposition rates of insect prey and nutrient availability for the plant, although this effect hasn't been fully studied or quantified. Without this species, protozoan populations limit prokaryotic biodiversity. Because of these indirect effects, the relationship between the purple pitcher plant mosquito and the purple pitcher plant is being further studied. Removing this species in natural populations may affect plant growth, but removal has not been extensively studied. (Bradshaw, 1980; Brown, et al., 1995; Counihan, et al., 2011; Fang, 2010; Hard, et al., 1993; Mahmood and Crans, 1998; terHorst, 2010)

Mutualist Species
  • Sarrecenia purpurea

Economic Importance for Humans: Positive

There is little evidence to suggest any positive interactions between this species and humans.

Economic Importance for Humans: Negative

This species is not known to be of any negative importance to humans.

Conservation Status

This species has no special conservation status but is used as an example to defend mosquitoes across the globe as it has a great impact within its ecosystem. (Fang, 2010)

Contributors

Luke Donahue (author), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

diapause

a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

internal fertilization

fertilization takes place within the female's body

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polarized light

light waves that are oriented in particular direction. For example, light reflected off of water has waves vibrating horizontally. Some animals, such as bees, can detect which way light is polarized and use that information. People cannot, unless they use special equipment.

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

sanguivore

an animal that mainly eats blood

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Bradshaw, W. 1980. Thermoperiodism and the thermal environment of the pitcher-plant mosquito, Wyeomyia smithii. Oecologia, 46/1: 13. Accessed July 30, 2012 at http://www.jstor.org/stable/10.2307/4216121.

Bradshaw, W. 1986. Variable iteroparity as a life-history tactic in the pitcher-plant mosquito Wyeomyia smithii. Evolution, 40/3: 471-478. Accessed July 30, 2012 at http://www.jstor.org/stable/10.2307/2408570.

Bradshaw, W., C. Holzapfel, P. Armbruster. 1997. Fitness consequences of the hibernal diapause in the purple pitcher plant mosquito, Wyeomyia smithii. Ecology, 79/4: 1458-1462. Accessed July 30, 2012 at http://www.jstor.org/stable/10.2307/176758.

Bradshaw, W., C. Holzapfel, T. Davison. 1998. Hourglass and rhythmic components of photoperiodic time measurement in the pitcher plant mosquito, Wyeomyia smithii. Oecologia, 117/4: 486-495. Accessed July 30, 2012 at http://www.jstor.org/stable/4222191.

Bradshaw, W., C. Holzapfel, M. Quebodeaux. 2003. The contribution of an hourglass timer to the evolution of photoperiodic response in the pitcher-plant mosquito, Wyeomyia smithii. Evolution, 57/10: 2342-2349. Accessed July 30, 2012 at http://www.jstor.org/stable/3448785.

Brown, K., E. Burkett, G. Johnson, M. Plaxton. 1995. The relationship between Wyeomia smithii and Metriocnemus knabi larvae and the insectivorous plant, Sarracenia purpurea. University of Michigan, Biological Station, Spring Term. Accessed July 30, 2012 at http://deepblue.lib.umich.edu/handle/2027.42/54580.

Counihan, J., K. Heuglin, C. Wagner, S. Gadomski, P. Zani, B. Fried. 2011. The effect of diapause on neutral lipids in the pitcher-plant mosquito Wyeomyia smithii as determined by HPTLC-densitometry. Journal of Planar Chromatography - Modern TLC, 24: 3.

Crans, W. 2010. "Wyeomyia smithii (Coquillett)" (On-line). Rutgers Center for Vector Biology. Accessed July 30, 2012 at http://www-rci.rutgers.edu/~insects/sp27.htm.

Fang, J. 2010. Ecology: A world without mosquitoes. Nature, 466: 432-434. Accessed July 30, 2012 at http://www.nature.com/news/2010/100721/full/466432a.html.

Frank, H. 1986. Bromeliads as ovipositional sites for Wyeomyia mosquitoes: Form and color influence behavior. The Florida Entomologist, 69/4: 728-742. Accessed July 30, 2012 at http://www.jstor.org/stable/3495221.

Göpfert, M., H. Breigel, D. Robert. 1999. Mosquito hearing: sound-induced antennal vibrations in male and female Aedes aegypti. The Journal of Experimental Biology, 202, Pt 20: 2727-2738. Accessed July 30, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/10504309.

Hard, J., W. Bradshaw, C. Holzaphel. 1993. The genetic basis of photoperiodism and its evolutionary divergence among populations of the pitcher-plant mosquito, Wyeomyia smithii. The American Naturalist, 142/3: 457-473. Accessed July 30, 2012 at www.jstor.org/stable/10.2307/2462653.

Harzch, S., G. Hafner. 2006. Evolution of eye development in arthropods: Phylogenetic aspects. Arthropod Structure and Development, 35/4: 319-340. Accessed July 30, 2012 at http://www.sciencedirect.com/science/article/pii/S1467803906000570.

Kostal, V. 2011. Insect photoperiodic calendar and circadian clock: Independence, cooperation, or unity?. Journal of Insect Physiology, 57/5: 538-556. Accessed July 30, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/21029738.

Lounibos, L., V. Van Dover, G. O'Meara. 1982. Fecundity, autogeny, and the larval environment of the pitcher-plant mosquito, Wyeomyia smithii. Oecologia, 55/2: 160-164. Accessed July 30, 2012 at http://www.jstor.org/stable/4216808.

Mahmood, F., W. Crans. 1998. Life history characteristics of Wyeomyia smithii from New Jersey. Journal of Vector Ecology, 24/1: 70-77. Accessed July 30, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/10436880.

Moer, J., C. Istock. 1980. Ecology and evolution of the pitcher-plant mosquito. Journal of Animal Ecology, 49/3: 775-792. Accessed July 30, 2012 at http://www.jstor.org/stable/4226.

Rook, E. 2004. "Sarracenia purpurea/Pitcher plant" (On-line). Flora, fauna, earth, and sky... The natural history of the northwoods. Accessed July 30, 2012 at http://www.rook.org/earl/bwca/nature/aquatics/sarracenia.html.

terHorst, C. 2010. Evolution in response to direct and indirect ecological effects in pitcher plant inquiline communities. The American Naturalist, 176/6: 675-685. Accessed July 30, 2012 at http://www.jstor.org/stable/10.1086/657047.