| Nezara viridula | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hemiptera |
| Suborder: | Heteroptera |
| Infraorder: | Pentatomomorpha |
| Superfamily: | Pentatomoidea |
| Family: | Pentatomidae |
| Genus: | Nezara |
| Species: | N. viridula |
| Binomial name | |
| Nezara viridula Linnaeus, 1758 |
|
Nezara viridula, commonly known as the southern green stink bug (USA) or green vegetable bug (Australia & New Zealand), is a plant-feeding stink bug. Although believed to have originated in Ethiopia, it can now be found around the world.[1] Because of its preference for certain species of legumes, such as beans and soybeans, it is an economically important pest on such crops.[2]
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Adults are approximately a centimeter long, bright green and shield-shaped. They differ from the similar N. hilaris species by the shape of their scent gland openings, which are short and wide in N. viridula, and narrow and long in N. hilaris.[1]
Several distinct morphs can be distinguished by the pattern of their exoskeleton coloration. The back can be completely green in one morph, the other has three parallel white spots on the scutellum, and the third has white front margins on the head and the thorax.
Nezara viridula reproduces throughout the year in tropics, and except for the winter time, in temperate zones as well. The female lays 30 to 130 eggs at a time, in the form of an egg mass glued firmly to the bottom of a leaf. The eggs are barrel-shaped, with an opening on the top.[1] The eggs take between 5 and 21 days to develop, depending on the temperature.[3] The newborn larvae gather near the empty eggs and do not feed until three days later, after the first moult. They moult five times before reaching maturity, increasing in size each time. Each instar stage lasts about a week, except for the last one before the metamorphosis, which is a day longer.[1] Up to four generations can develop in one year, with eggs developing into adults in as few as 35 days in mid-summer. Up until their third moult the larvae aggregate together on the host plant, the purpose of this aggregation is probably pooling of chemical defenses against predators, for example ants.[3]
It is a highly polyphagous herbivore, able to feed on plants from over 30 families, both monocots and dicots.[3] It has a preference for legumes, preferring to feed on plants that are fruiting or forming pods.[3]
The most important factor limiting the population in temperate zone is winter cold. Mortality of overwintering individuals is between 30 and 80%, and the population cannot survive in areas where the average mid-winter temperature is below 5ºC.[4] Females are more likely to survive the winter than males, as are larger individuals and those that develop reddish-brown coloration.[3] In recent decades, the species seems to be expanding its range towards the north, possibly because of global warming.[4][5] The animal's ability to survive the winter also depends on the timely onset of diapause.
Nezara viridula is a cosmopolitan species, living in tropical and subtropical regions of Americas, Africa, Asia, Australasia and Europe between 45 degrees north and 45 degrees south.[3] Its exact origin is unknown, but it is believed to have originated from the Ethiopia region of East Africa, from where it has spread around the world thanks to its strong flight and human trade routes.[3]