Southern Green Stink Bug

Appearance

The adult males can reach a body length of about 12.1 millimetres, while females are bigger, reaching a size of about 13.1 millimetres. The body is usually bright green and shield-shaped and the eyes are usually reddish, but they may also be black. There is a row of three white spots on the scutellum. They differ from the similar green stink bug by the shape of their scent gland openings, which are short and wide in "N. viridula", and narrow and long in the green stink bug.

Habitat

It is a highly polyphagous herbivore, able to feed on plants from over 30 families, both monocots and dicots. It has a preference for legumes, preferring to feed on plants that are fruiting or forming pods.

The most important factor limiting the population in temperate zones 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 5 °C. Females are more likely to survive the winter than males, as are larger individuals and those that develop reddish-brown coloration. In recent decades, the species seems to be expanding its range towards the north in the northern hemisphere, possibly because of global warming. The animal's ability to survive the winter also depends on the timely onset of diapause.

Evolution

"Nezara viridula" reproduces throughout the year in tropics. In temperate zones this species presents a reproductive winter diapause, associated with a reversible change of body colouration from green to brown or russet.

When ready to mate "N.viridula" sound 100 Hz vibration with a "tymbal" composed of a fused first and second terga that allow bi-directional communication to any "Nezara" standing on the same plant so they could find each other. 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. The eggs take between 5 and 21 days to develop, depending on the temperature. 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. 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.