''Mythimna separata'', the northern armyworm, oriental armyworm or rice ear-cutting caterpillar, is a

moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

of the family Noctuidae. It is found in China, Japan,

South-east Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, eastern Australia,

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, and some

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

islands. It is one of the major pests of maize in Asia. The species was first described by Francis Walker in 1865.

Etymology

They term "armyworm" is used because of their habit to spread out in a line across a lawn or pasture, and slowly "march" forward, consuming the foliage they encounter. Mythimna separata

Description

The

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

is 35–50 mm. Males lack paired tufts on the basal segment of the abdomen below. The forewings are greyish yellow with a dark-grey or reddish-yellow tinge. The round and reniform spots are light or yellowish with indistinct edges, whereas reniform spot with white point at lower margin. External wing margin blackened obliquely from top backward, with dark stroke and with a row of dark points. Hindwings are grey, with dark external margin. Antennae thread like. Eggs are spherical and milky white with a thinly reticulate surface. Larvae usually have six

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

s, rarely seven. It reaching 40 mm in length at its last instar. Larva has two wide black-brown and one intermediate light dorsal stripe, with black-brown lateral stripe along spiracle line. spiracles brown with black rim. Pupae are yellowish brown and shiny.

Ecology

The moth flies from January to April depending on the location. The larvae feed on a range of agricultural plants like '' Zea mays'', '' Sorghum bicolor'' and ''

Oryza sativa ''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yan ...

'' and are thus considered a pest. Caterpillars do not feed on '' Momordica charantia'' due to the presence of the

triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi all produce triterpenes, including squal ...

glucoside called

momordicine A momordicine is any of several compounds found in the bitter melon vine, ''Momordica charantia''. They are glycosides of cucurbitane derivatives.Daniel Bisrat Mekuria, Takehiro Kashiwagi, Shin-ichi Tebayashi, and Chul-Sa Kim (2006)"Cucurbitane Gl ...

II, which is a natural inhibitor of caterpillar actions.

Infestations

China experiences periodic outbreaks of northern armyworm infestation. The outbreak in 2012 was particularly severe.

Control

Larva can be hand picked and adults can attracted using pheromones. Regulation of water level in the fields, and removal of alternate hosts from the field are also effective. Among biological controls, ducks are good; they can locate larvae hiding in the soil or at the base of plants easily and prey on them. Introduction of '' Cotesia ruficrus'', and '' Eupteromalus parnarae'' also parasitized the larva. Selective pesticides and weedicides can also used in the field. Integrated pest management methods undertaken by governments.

References

External links

Species infoUniprot
{{Taxonbar, from=Q4426559 Mythimna (moth) Moths of Asia Moths of Oceania Moths described in 1865 Taxa named by Francis Walker (entomologist) Insect pests of millets