''Mythimna unipuncta'', the true armyworm moth, white-speck moth, common armyworm, or rice armyworm, is a species of

moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...

in the family

Noctuidae The Noctuidae, commonly known as owlet moths, cutworms or armyworms, are a family (biology), family of moths. Taxonomically, they are considered the most controversial family in the superfamily Noctuoidea because many of the clades are constantly ...

. The species was first described by

Adrian Hardy Haworth Adrian Hardy Haworth (19 April 1767, in Kingston upon Hull, Hull – 24 August 1833, in Chelsea, London, Chelsea) was an England, English entomologist, botanist and carcinologist. Family The younger son of Benjamin Haworth, of Haworth Hall and ...

in 1809. ''Mythimna unipuncta'' occurs in most of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

south of the

Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...

, as well as parts of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

, and

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

. Although thought to be

Neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In biogeogra ...

in origin, it has been introduced elsewhere, and is often regarded as an

agricultural pest A pest is any organism harmful to humans or human concerns. The term is particularly used for creatures that damage crops, livestock, and forestry or cause a nuisance to people, especially in their homes. Humans have modified the environment fo ...

. They are known as armyworms because the caterpillars move in lines as a massive group, like an army, from field to field, damaging

crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, fibre, or fuel. When plants of the same species a ...

.Palmer, Geoff (July 23, 2012)
"Pest Alert - Armyworms Round Two Hit Hay and Corn Crops"
. ''Agriculture and Market''. The true armyworm has a distinct migration pattern in which they travel north in the spring and south in the fall to ensure that mating occurs in a favorable environment in the summer. While progressing through the life cycle stages of egg,

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

, and adult, this species must avoid attack from

predatory Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

bugs, birds, wasp and fly parasitoids, and bacterial and fungal diseases. As

polygamous Polygamy (from Late Greek , "state of marriage to many spouses") is the practice of marrying multiple spouses. When a man is married to more than one wife at the same time, it is called polygyny. When a woman is married to more than one h ...

insects, females release

sex pheromone Sex pheromones are pheromones released by an organism to attract an individual of the same species, encourage them to mate with them, or perform some other function closely related with sexual reproduction. Sex pheromones specifically focus on ind ...

s and choose multiple males as mates. The production and release of the pheromones are influenced by temperature, photoperiod, and the juvenile hormone.McNeil, Jeremy N. (1986). "Calling Behavior: Can It Be Used to Identify Migratory Species of Moths". ''The Florida Entomologist''. vol. 69, no. 1, pp. 78–84. . Hearing is an important sense for the true armyworm, necessary for mating and evading bat predation.

Geographic range

''M. unipuncta'' are commonly found around the world including the

Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...

southern Europe Southern Europe is also known as Mediterranean Europe, as its geography is marked by the Mediterranean Sea. Definitions of southern Europe include some or all of these countries and regions: Albania, Andorra, Bosnia and Herzegovina, Bulgaria, C ...

central Africa Central Africa (French language, French: ''Afrique centrale''; Spanish language, Spanish: ''África central''; Portuguese language, Portuguese: ''África Central'') is a subregion of the African continent comprising various countries accordin ...

, and

western Asia West Asia (also called Western Asia or Southwest Asia) is the westernmost region of Asia. As defined by most academics, UN bodies and other institutions, the subregion consists of Anatolia, the Arabian Peninsula, Iran, Mesopotamia, the Armenian ...

. In

, they inhabit areas east of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...

and in northern

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

.Capinera, John L. (October 2006)
"Armyworm, ''Pseudaletia unipuncta'' (Haworth) (Insecta: Lepidoptera: Noctuidae)"
University of Florida.

Food resources

Larvae

Larvae feed and damage on a variety of

Graminae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated in ...

(weedy grasses) and other crops. * ''

Hordeum vulgare Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikelets ...

'' – barley *

Maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

– corn *

Oats The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have been domesticated as a secondary crop, as their seed ...

Rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

Rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is grown principally in an area from Eastern and Northern Europe into Russia. It is much more tolerant of cold weather and poor soil than o ...

Sorghum ''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a species in the Poaceae, grass genus ''Sorghum (genus), Sorghum'' cultivated for its grain. The grain i ...

Sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...

Wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

Alfalfa Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial plant, perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, ...

Artichoke The artichoke (''Cynara cardunculus'' var. ''scolymus''),Rottenberg, A., and D. Zohary, 1996: "The wild ancestry of the cultivated artichoke." Genet. Res. Crop Evol. 43, 53–58. also known by the other names: French artichoke, globe artichoke, ...

Bean A bean is the seed of some plants in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying (a ''pulse''), but fresh beans are also sold. Dried beans are traditi ...

Cabbage Cabbage, comprising several cultivars of '' Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.& ...

Carrot The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild ...

Celery Celery (''Apium graveolens'' Dulce Group or ''Apium graveolens'' var. ''dulce'') is a cultivated plant belonging to the species ''Apium graveolens'' in the family Apiaceae that has been used as a vegetable since ancient times. The original wild ...

Cucumber The cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the family Cucurbitaceae that bears cylindrical to spherical fruits, which are used as culinary vegetables.Lettuce Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae mostly grown as a leaf vegetable. The leaves are most often used raw in Green salad, green salads, although lettuce is also seen in other kinds of food, such as sandwiche ...

Onion An onion (''Allium cepa'' , from Latin ), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus '' Allium''. The shallot is a botanical variety of the onion which was classifie ...

Parsley Parsley, or garden parsley (''Petroselinum crispum''), is a species of flowering plant in the family Apiaceae that is native to Greece, Morocco and the former Yugoslavia. It has been introduced and naturalisation (biology), naturalized in Eur ...

Pepper Pepper(s) may refer to: Food and spice * Piperaceae or the pepper family, a large family of flowering plants ** Black pepper ** Long pepper ** Kampot pepper * ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanacea ...

Sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant in the morning glory family, Convolvulaceae. Its sizeable, starchy, sweet-tasting tuberous roots are used as a root vegetable, which is a staple food in parts of ...

Adults

Adults feed on the

nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...

of various types of flowers and will eat ripe or decaying fruit.

Life history

Life cycle

In a given year, there can be two to three generations, each generation requiring 30–50 days to complete.

Egg

Adults

oviposit The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

in groups of 2 to 5 rows on dry leaves and grass, especially between the leaf sheath and blade. Females may deposit up to 80 eggs per cluster, leading to highly dense larvae populations. Total reproductive capacity for females is between 500-1500 eggs. The egg stage lasts on average 3.5 days in warmer weather and 6.5 days in cooler weather. The eggs appear to be a white or yellowish color but change to a gray hue right before

eclosion A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

. A sticky material on the surface of the egg sticks to surrounding foliage and helps hide the eggs.

Larvae

The true armyworm larval stage lasts at least six

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

s but may extend to nine. The

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

grows from 4 to 35 mm within this stage. The larval stage lasts about 20 days in warmer weather and 30 days in cooler weather. When the larvae hatch, they feed on the foliage on which they were laid, but if disrupted, larvae release silk and fall into the soil. Larvae in the later instars are nocturnal and will often hide under the soil for protection during daylight. The larvae are usually grayish green or grayish brown but have characteristic longitudinal stripes along the length of the body. Seitz describes it "The larva is green to brown, freckled with darker; the lines obscure; dorsal line almost lost in a dark clouding; subdorsal lines plainer, with the upper edge diffuse: lateral and spiracular lines white." See also Hacker et al.

Pupa

Pupation occurs underground in a silken case produced by the larvae. The pupa is usually 13–17 mm long and 5–6 mm wide. A pair of hooks protrude from the abdomen. The pupal stage lasts 7–14 days in warmer conditions and up to 40 days in cooler conditions. The color of the pupae is initially yellowish brown but changes to a mahogany-brown hue.

Adult

The adult true armyworms are

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

insects. A complete generation from egg to adult lasts 30–50 days. Life expectancy in warm conditions is 9 days in males and 10 days in females. In cooler conditions, life expectancy is 19 days in males and 17 days in females. Adults have a

wingspan The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the opposite wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingsp ...

of approximately 4 cm. Black dots line the anterior edge of the forewings, making them look very pointed. There is a centrally located darker area that has several white dots as well. The hindwings have a more grayish tint. In Seitz it is described thus- The forewings are ochreous grey, freckled with darker grey, often suffused with rufous and with obscure markings. The orbicular and reniform stigmata are pale or yellowish, the latter with a white dot at lower end. There is an outer row of dark dots on veins, joined by a dark streak from apex. The hindwings are fuscous grey, paler basewards, the veins dark.

Migration

''P. unipuncta'' are seasonal migratory moths that travel north in the spring to escape high temperatures and south in the winter to escape cold temperatures. It has been shown that females reared in high temperatures mated less often, and those that did copulate experienced a 10-fold decrease in fertile egg production compared to females reared in temperate conditions. This could indicate an evolutionarily beneficial reason for this migratory behavior. Females flying in the spring northern migration were found to have developed

ovaries The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

and mating experience whereas females flying in the fall southern migration were found to have little or no reproductive organ development. This lends further support to

mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. '' Copulation'' is the union of the sex organs of two sexually repr ...

being favored in the summer months.McNeil, Jeremy N. (1987). "The True Armyworm, ''Pseudaletia unipuncta'': A Victim of the Pied Piper or a Seasonal Migrant?" ''Insect Science and Its Application'', vol. 8, no. 4-5-6, pp. 591–597. .

Enemies

Predators

Many species feed on armyworm larvae. These include

ground beetle Ground beetles are a large, cosmopolitan distribution, cosmopolitan family (biology), family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it ...

s, who share the same habitat in the soil, in addition to predatory bugs,

ants Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

, and

spiders Spiders (order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species di ...

. The

bobolink The bobolink (''Dolichonyx oryzivorus'') is a small New World blackbird and the only member of the genus ''Dolichonyx''. An old name for this species is the "rice bird", from its tendency to feed on cultivated grains during winter and migration. ...

, a small type of blackbird, has been nicknamed the "armyworm bird" in North America because of its predation on armyworms. Other birds that pose a predation risk are

crow A crow is a bird of the genus ''Corvus'', or more broadly, a synonym for all of ''Corvus''. The word "crow" is used as part of the common name of many species. The related term "raven" is not linked scientifically to any certain trait but is rathe ...

s and

starling Starlings are small to medium-sized passerine (perching) birds known for the often dark, glossy iridescent sheen of their plumage; their complex vocalizations including mimicking; and their distinctive, often elaborate swarming behavior, know ...

Parasitoids

There are over 60

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

and

fly Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

species that terrorize the true armyworm. The larvae of the

parasitoids In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

live in the true armyworm and ultimately kill the host. Some examples of wasp parasitoids include '' Meteorus autographae'' and ''

Cotesia ''Cotesia'' is a genus of braconid wasps first described by Peter Cameron in 1891. Some species parasitize caterpillars of species considered pests, and are used as biocontrol agents. ''Cotesia congregata'' parasitizes the tomato and the toba ...

marginiventris''.

Diseases

Bacterial Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the ...

and

fungal A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradit ...

diseases can harm the true armyworm especially in densely populated areas. In particular, the fungus ''

Metarhizium anisopliae ''Metarhizium anisopliae'' is a fungus, the type species in the ''Metarhizium'' genus. It grows naturally in soils throughout the world and causes disease in various insects by acting as a parasitoid. Ilya Ilyich Mechnikov, Ilya I. Mechnikov nam ...

'' has been recorded.

Viral The word ''Viral'' means "relating to viruses" (small infectious agents). It may also refer to: Viral behavior, or virality Memetic behavior likened that of a virus, for example: * Viral marketing, the use of existing social networks to spre ...

infections including several granulosis, cytoplasmic polyhedrosis, and nuclear polyhedrosis can wipe out entire populations, especially when coupled with poor food and weather conditions.

Mating

Female calling behavior

When females are ready to mate, they release

sex pheromones Sex pheromones are pheromones released by an organism to attract an individual of the same species, encourage them to mate with them, or perform some other function closely related with sexual reproduction. Sex pheromones specifically focus on ind ...

through a behavior known as calling. On average, this behavior is displayed around 4–6 days after emergence; age of calling onset is determined by ambient temperature and

photoperiod Photoperiod is the change of day length around the seasons. The rotation of the earth around its axis produces 24 hour changes in light (day) and dark (night) cycles on earth. The length of the light and dark in each phase varies across the season ...

. Low temperatures and short photoperiods delay the calling period, but higher temperatures and long photoperiods trigger calling period sooner after emergence These are consistent with the yearly changes in the behavior of ''P. unipuncta'': the moth is in migration in the fall and spring seasons, and ''P. unipuncta'' prefer to mate in the summer. Females can mate about 5 or 6 times in their lifetime.Fitzpatrick, S. M. & McNeil, J. N. (1989). "Lifetime Mating Potential and Reproductive Success in Males of the True Armyworm, ''Pseudaletia unipuncta'' (Haw.) (Lepidoptera: Noctuidae)". ''Functional Ecology'', vol. 3, no. 1, pp. 37–44. .

Juvenile hormone

The

juvenile hormone Juvenile hormones (JHs) are a group of acyclic sesquiterpenoids that regulate many aspects of insect physiology. The first discovery of a JH was by Vincent Wigglesworth. JHs regulate development, reproduction, diapause, and polyphenisms. In ...

, released by the corpora allota, is necessary for females to produce and release

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

s through their calling behavior. The

corpora allata In insect physiology and anatomy, the corpus allatum (plural: corpora allata) is an endocrine gland that generates juvenile hormone; as such, it plays a crucial role in metamorphosis. Surgical removal of the corpora allata (an allatectomy) can cau ...

is an

endocrine gland The endocrine system is a network of glands and organs located throughout the body. Along with the nervous system, it makes the neuroendocrine system, which controls and regulates many of the body's functions. Endocrine glands are ductless gland ...

that when removed, causes pheromone synthesis and calling behavior to cease. The juvenile hormone also plays a role in ovarian development. When the corpora allata is removed in females, the

are underdeveloped, whereas in insects with intact corpora allata, mature

gametes A gamete ( ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the Ge ...

are formed. The ovaries are not necessary for pheromone production or release, though, because removing the ovaries did not impact pheromone levels in the insect. Neuroendocrine control of calling behavior allows ''P. unipuncta'' to determine when mating is favorable or not.Cusson, M. & McNeil, J. N. (1989). "Involvement of Juvenile Hormone in the Regulation of Pheromone Release Activities in a Moth". ''Science'', vol. 243, no. 4888, pp. 210–212. .

Female mate choice

Males have specific scent organs called

hair-pencil Hair-pencils and coremata are pheromone signaling structures present in lepidopteran males. Males use hair-pencils in courtship behaviors with females. The pheromones they excrete serve as both aphrodisiacs and tranquilizers to females as well as ...

s that contain

benzyl alcohol Benzyl alcohol (also known as α-cresol) is an aromatic alcohol with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn" (not to be confused with "Bz" which is used for benzoyl), thus benzyl alcohol is denoted as BnOH. Benzyl a ...

in young males as well as

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is among the simplest aromatic aldehydes and one of the most industrially useful. It is a colorless liquid with a characteristic almond-li ...

and

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

. Female antennae can detect benzaldehyde and acetic acid. It has been shown that females are more likely to choose males with intact hair-pencils than males with hair-pencils removed. However, these scent organs are not necessary for copulation as a significant portion of females will still mate with males with no hairpencils.Fitzpatrick, Sheila M. & McNeil, Jeremy N. (1988). "Male Scent In Lepidopteran Communication: The Role of Male Pheromone in Mating Behaviour of ''Pseudaletia unipuncta'' (Haw.) (Lepidoptera: Noctuidae)". ''Memoirs of the Entomological Society of Canada'', vol. 120, no. S146, pp. 131–151. . The amount of sex pheromone released by males decreases as the number of matings increase. It has been shown that females reject males with lower pheromone levels. Females reject males in multiple ways. First, the female may walk or fly away. If the male has already clasped the female, the female will arch her abdomen and walk or fly away in the opposite direction until the male releases his grip.

Female abdominal marks

Non-virgin females are often marked on the abdomen after mating by the male. However, many non-mated females have markings. This may be from males clasping the females, leaving a mark, but unsuccessfully copulating.

Male mating habits

Males wait on average three days after eclosion to begin mating. The delay can be attributed to the time it takes to transfer sperm to the duplex, an accessory gland. After every mating, the male must wait 6 hours for the duplex to be refilled in order to mate again. Males have at least two partners in their lifetime. Males who have a higher reproductive rate and mate more frequently suffer from a shorter lifespan than virgin males or males that mate less frequently. There is a limit to the number of mates a male can have, though, because after approximately the seventh mating, eggs in females are not properly developed due to deficient and limited ejaculate. In the fall, males do not respond to female sex pheromones, indicating that males also delay mating before winter and during migration.

Preventing cross-species mating

''M. unipuncta'' males can distinguish females of their own species from those of other species by recognizing the contents of the female sex pheromone. One study looked at how ''M. unipuncta'' males responded to lures containing their own pheromone and to lures containing the sex pheromone of a

sympatric In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...

species known as ''

Sesamia nonagrioides ''Sesamia'' is a genus of moths of the family Noctuidae erected by Achille Guenée in 1852. Most but not all of its species are Afrotropical in distribution, with a preference for humid, open habitats. Larvae are stemborers, and several species o ...

.'' When (Z)-11-hexadecenal, a component found in the sex pheromones of ''S. nonagrioides'' females, was added to the lures, the ''M. unipuncta'' males were less attracted. Therefore, the males' ability to detect certain acetates in the pheromones serves as a reproductive isolating mechanism and prevents cross-species mating.

Physiology

Hearing

It has been suggested that hearing is important for mating. Females will often increase their wing fanning frequency when males are approaching. In response to female sex pheromones, males may produce a low-frequency trembling noise. When echolocation sounds of

bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

s were simulated around ''P. unipuncta'', females stopped calling behavior and males stopped flapping their wings. This species uses their

tympanal organ A tympanal organ (or tympanic organ) is a hearing organ in insects, consisting of a tympanal membrane ( tympanum) stretched across a frame backed by an air sac and associated sensory neurons. Sounds vibrate the membrane, and the vibrations are s ...

to stop mating behavior in the presence of predators.Acharya, L. (January 1, 1998). "Predation Risk and Mating Behavior: The Responses of Moths to Bat-like Ultrasound". ''Behavioral Ecology'', vol. 9, no. 6, pp. 552–558. .

Interactions with humans

Pest of crop plants

The true armyworm is considered an agricultural pest. During the caterpillar stage, the larvae feed on leaves. This species prefers grass weeds, (such as '' Urochloa ramosa'',) but when those are depleted, they quickly move to crops. Outbreaks of true armyworm swarms are not uncommon. In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, the western regions of

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experienced an outbreak of common armyworms around May 2012. While the infestation remained fairly localized, it obliterated several hay and corn fields. When fields are prone to being attacked, the crops should be checked periodically, especially in the first two weeks of June.

Pheromone trap A pheromone trap is a type of insect trap that uses pheromones to lure insects. Sex pheromones and aggregating pheromones are the most common types used. A pheromone-impregnated lure is encased in a conventional trap such as a bottle trap, delta ...

s can be used to gauge size of adult populations. The damage on leaves is a telling sign that

insecticides Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, in ...

and baits may be useful in combating an outbreak.Calvin, Dennis. (July 2009)
"Armyworm as a Pest of Field Corn
. Department of Entomology (Penn State University).

Gallery

image:Mythimna unipuncta female dorsal.jpg, Female, dorsal view image:Mythimna unipuncta female ventral.jpg, Female, ventral view image:Mythimna unipuncta male dorsal.jpg, Male, dorsal view image:Mythimna unipuncta male ventral.jpg, Male, ventral view Image:Mythimna unipuncta (Haworth).jpg, Caterpillar Image:Mythimna_unipuncta.larva.jpg, Caterpillar # ''The flight season refers to the

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. This may vary in other parts of the range.''

References

*Waring, Paul & Townsend, Martin (2006). ''Nachtvlinders, veldgids met alle in Nederland en België voorkomende soorten''. Baarn.

External links

* * Taxonomy
''Lepiforum e.V.''

''De Vlinderstichting''
{{Taxonbar , from=Q310072 Mythimna (moth) Moths described in 1809 Agricultural pest insects Moths of Africa Moths of Asia Moths of Oceania Moths of North America Moths of South America Moths of Europe Moths of the Middle East Lepidoptera of Jamaica Taxa named by Adrian Hardy Haworth Insect pests of millets