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Nezara viridula, commonly known as the southern green stink bug (USA), southern green shield bug (UK) or green vegetable bug (Australia and New Zealand), is a herbivore Pentatomidae. Believed to have originated in Ethiopia, it can now be found across the world.Squitier J.M. (1997, updated 2007) « Southern green stink bug» Featured creatures, University of Florida Institute of Food and Agricultural services. Because of its preference for certain species of , such as and , it is an economically important pest on such crops.Panizzi A.R. et al. (2000). Stink bugs (Pentatomidae). In: Schaefer C.W. & Panizzi A.R. (eds.). Heteroptera of economic importance, str. 421-747. Boca Raton: CRC Press.
When ready to mate N. viridula produce 100 Hz vibrations with a "tymbal" composed of fused first and second terga (not to be confused with tymbal of cicadas) 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 nymphs gather near the empty eggs and do not feed until three days later, after the first ecdysis. They moult five times before reaching maturity, increasing in size each time. Each instar stage lasts about a week, except for the last one 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 nymphs aggregate together on the host plant; the purpose of this aggregation is probably pooling of chemical defenses against such as .
The most important factor limiting the population in 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.Musolin D.L. (2005). « The Southern Green Shield Bug Nezara viridula (L.) expands its distribution range, not only in the U.K.» Het News - Newsletter of the Heteroptera Recording Schemes. Retrieved on 2008-10-14. 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. The animal's ability to survive the winter also depends on the timely onset of diapause.
Seasonal changes in temperature provide important cues to N. viridula that affect growth, reproduction, and fitness. Warmer temperatures in early spring can increase egg production and accelerate development. Warmer temperatures in the late summer can often be stressful, potentially stunting growth and decrease survival. Finally, warmer winter temperatures can increase survival. In the winter, there are differences in survivorship depending on size in N. viridula, where larger females tend to have higher survival rates. Temperature, in combination with other abiotic factors, can therefore have substantial influence on stink bugs across their lifetime.
Other environmental effects
Short photoperiods during the nymphal stage can increase development when coupled with cooler temperatures, but decrease developmental time when coupled with hot temperatures. Humidity can also affect fitness in N. viridula. In low humidity conditions, eggs require more time to hatch. In high humidity conditions, particularly when coupled with high temperatures, survival and longevity decrease.
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