Orange Black Stink Bug


Gum Tree Shield Bug - Theseus modestus

Family Pentatomidae

This page contains pictures and information about Gum Tree Shield Bugs in genera Theseus that we found in the Brisbane area, Queensland, Australia.

Body length 15mm
This shield bug looks very similar to the Common Gum Tree Shield Bug but about half the body size. Both can be found on the gum tree trunk. However, this shield bug is a bit less common in Brisbane.
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The antenna is clearly 5-segmented on the relatively long head. The juga do not surpassing apex of anteclypeus. the body colours are dark brown punctuations on creamy-white. There are five longitudinal lines on head.   
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They are usually found feeding on large gum tree trunks. Adults can be found on stems and leaves as well. 
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We believe they are on leaves for looking for their mates. 
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Because those difference species of Gum Tree Shield Bugs look so similar and live in the same environments, we believe they may have form a Mullerian mimicry complexIn Mullerian mimicry, the model is not defined and several unpalatable species share warning colors or patterns to evade predation. Both models and mimics are toxic. Several species from several different orders may comprise a mimicry complex. The advantage is that the predators need only encounter one form to shun the entire complex.


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4th instars 
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4th instars 
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5th instars 
We believed they are the nymphs of this species.

1. Insects of Australia, CSIRO, Division of Entomology, Melbourne University Press, 2nd Edition 1991, pp 509.
2. FaunaKeys - Stink Bugs of Australia,  Australian Museum online 2003.
3. Theseus modestus - Australian Biological Resources Study, Department of the Environment and Heritage, Commonwealth of Australia 2005.
4. Poecilometis modestus Stål, 1865 -  Types of Heteroptera, Swedish Museum of Natural History
5. Theseus Stål, 1867 - by Gerry Cassis, Emma Betts and Michael Elliott, Stink Bugs, Fauna Net, Australian Museum 2002. 
6. Plant-feeding and Other Bugs (Hemiptera) of South Australia. Heteroptera-Part II - Gross, G.F. (1976). Adelaide: A.B. James, p285.

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Last updated: August 10, 2010.