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From egg to adult moth! How thrilling is the life of a true army moth?
The true army moth (Mythimna unipuncta) is a species of insect from the family Noctuidae. The life cycle of this creature is full of drama and challenges. From egg to adult, it not only faces the threat of natural enemies, but also needs to find the right environment to ensure successful reproduction.
Biological features and habitats
This moth is widespread in North and South America, most of Europe, Africa, and parts of Asia. In North America, they are found mainly east of the Rocky Mountains and north into Canada. The larval stage of the true armyworm moth, commonly known as army bugs, can cause significant damage to crops, making it considered one of the agricultural pests.
Army bugs live up to their name because they gather in large groups and migrate in army-like swarms, wreaking havoc on farmland.
Four stages of the life cycle
The life cycle of the true army moth is divided into four stages: egg, larva, pupa and adult. Among them, there are usually two to three generations of production in a year, and the production cycle of each generation takes about 30 to 50 days.
Egg laying
The female moth usually lays 50 to 80 eggs on dry leaves or grass. The eggs change color from white or yellowish to gray before hatching, and have a sticky substance on the surface that helps them hide among the surrounding vegetation.
Growth of larvae
The larval stage lasts about 20 days, during which time it undergoes at least six molts. The larvae are usually grey-green or grey-brown with distinct stripes on their bodies and show very active growth characteristics, growing from 4 to 35 mm.
Pupa Development
The larvae make silky pupae underground, a stage that lasts 7 to 14 days and changes color from yellow-brown to mahogany (reddish-brown). The pupae appear yellowish-brown at first, but quickly turn a darker color.
Characteristics of Adults
The adult is a nocturnal insect with a lifespan of about 9 to 10 days in a high temperature environment and up to 19 days in a lower temperature environment. The adult has a wingspan of about 4 cm, with the forewings having black spots and a dark area in the center, and the hindwings being grayish in tone.
Migration Behavior
True army moths have a very distinct migratory behavior, migrating north in the spring to escape the heat and south in the winter to escape the cold. This behavior not only ensures that they mate in the right environment, but also increases their reproductive success rate.
Mature female moths migrate north in the spring with well-developed ovaries, whereas female moths that migrate south in the fall often do not have well-developed reproductive organs.
Biological Enemies
True armyworms encounter many natural enemies during their life journey, including ground beetles, predatory insects, birds, etc. Perhaps most threatening, however, are the more than 60 species of parasitic wasps and flies that use the true armyworm as their primary host, extracting nutrients from it and causing the death of the host.
Reproductive Behavior
Female true armyworms release sex pheromones to attract males when the environment is right, which usually happens within 4 to 6 days before they lay eggs. Males also have their own scent organs, which are very important for reproduction.
Male males have to wait six hours after mating before they can mate again, showing their reproductive limitations.
Human Impact
Reflecting on humanity’s relationship with these creatures, the damage that true armyworms can cause to growing crops cannot be underestimated, especially in agricultural societies. Effective monitoring measures, including the use of sex pheromone traps, can detect adult populations early and action can be taken to prevent an infestation.
What unknown challenges and opportunities are hidden in the life cycle of the true army moth? Will it have unexpected impacts on crops and the ecological environment?
