Coreid Bugs
Wingless Coreid

Cotton Plant Bug - Aulacosternum nigrorubrum

Family Coreidae

This page contains pictures and information about Cotton Plant Bugs that we found in the Brisbane area, Queensland, Australia

Body length male 18mm, female 20mm

This Cotton Plant Bugs are easily found on the Hibiscus plants in our back yard. The bugs are red orange in colour with black legs. They are slow moving, always found sucking the juice from the young shoots or flower buds. 

The bugs are also known as False Cotton Stainer, as this name implies they are the pest on cotton. 

Followings are our records on the Cotton Plant Bug's life cycle. 
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Adult female                                                          Adult male                                                           Mating couple
Cotton Plant Bug adult females are a little bit larger than the adult male. The male has brighter orange wings colour. When mating, unlike other Coreid Bugs which facing tail to tail, their copulation occurs with the bodies in parallel and head close together.
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Mating bugs, 24 SEP                                            Eggs length 1.5mm, 5 OCT                                  1st instars, 4mm, 04 NOV
Those Cotton Plant Bugs suck juice from plants. They lay eggs on new fully grown leaf surface in a batches of 3-14. Those eggs are brown in colour with two black dots. They are 1 x 1.5 mm in size. 
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2nd instars, 5mm                                                  3rd instars, 7mm                                                  4th instars, 9mm
After about a month, we saw all the eggs hatched into small bugs. They are called nymphs. The are 5mm in body length. They have a pair of long antennae and three pair of long legs. Their heads are black, thoraxes are yellow and abdomens are red. They stay together for a few days. At this stage, they look like ants. 
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5th instars, 12mm, 22 NOV 
After three week they grew to half the size of an adult. They look similar to the adult except they are wingless. They grow periodically shedding their outer skin, which allow them to expand and make room for growing. Notice the wing buds become obvious. 
                                                                            03 DEC 2000 
A week later, we can see their wings buds start to grow longer from their back. Actually those young bugs live the same ways and share the same food as their adults.
A few days later, we find them start to change into an adults. This is the final stage of moulting. They become capable of reproduction and have wings. The photo shows the bug just come out from it last shedding skin (small photo). Its colour will change to the adult colour few hours later. 
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04 DEC 2000
Cotton Plant Bug is feeding on flower bud juice. All different bugs have one common characteristic: their sucking mouths. All of them suck juice from plants or other insects.  

The Native Food Plant

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Native Rosella - Hibiscus Heterophyllus
Along the Enoggera Trail in Brisbane Forest Park, there are many Native Rosella. On them we easily find the Cotton Plant Bugs, which suck sap from of all different kinds of Hibiscus.
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Bug's Life - In-complete Life Cycle

Bug's development is a good example of in-complete life cycle, or gradual metamorphosis. Let familiar with different stages of in-complete life cycle  by the following diagram.
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1. Studies on the biology, immature stages, and relative growth of some Australian bugs of the superfamily Coreoidea (Hemiptera: Heteroptera) - Kumar, R. 1966, Australian Journal of Zoology 14: 895-991 [908].

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Last updated: September 04, 2010.