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| Nymphs of Green Shield Backed Bug sitting on Red-Eyed Wattle. Note the seeds and the seed pods. |
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| Nymphs of Green Shield Backed Bug with the Red-Eyed Wattle pods. |
Location: Bunbury
Season: Early Summer
Class: Insecta
Order: Hemiptera
Suborder: Heteroptera
Infraorder: Pentatomomorpha
Superfamily: Pentatomoidea
Family: Scutelleridae
Coleotichus costatus
These colourful nymphs were found on Red-Eyed Wattle (Acacia cyclops).
Relationship between Red-Eyed Wattle and Green Shield Backed Bug
Red-Eyed Wattle has dry twisted pods within which lie glossy black seeds encircled by two folds of a large orange to bright red fleshy stalk-like structure. The black seed looks like an eye and the surrounding orange-red aril looks like a stalk, giving it the name Red-Eyed Acacia and the botanical name cyclops (stalk eyed).The seeds attract ants and birds. Birds like Honey-eaters and Wattle Birds feed on the seed, digesting the red aril and excreting the black seed which helps in dispersion of the seed and propagation of the plant. The interaction with ants is one of the most important mutualistic mechanisms for seed dispersal. Ants carry the seed with the encircling aril into their underground nests. The aril is nutritious but the ant cannot pierce the hard seed. The seeds are cast away, sometimes burst out of the nests during bush fires, helping the dispersal of the seed and propagation of the plant. This process is called Myrmecochory.
Red-Eyed Wattle is one of the known host plants for Green Shield Backed Bug. The nymphs and adults feed on the plant. Their piercing mouth parts are strong enough to penetrate the hard seed. The nymphs of the Green Shield Backed Bug resemble the seed and almost indistinguishable from the seeds unless examined closely. This a mimicry model. The insect nymph is at risk of predation from birds due to its bright colour. This has probably been exploited by the plant which mimics the insect to get the attention of birds for seed dispersal. Hence, the nymph may be the model and the seed may be the mimic.
The bugs have evolved to protect themselves. In order to deter the predators, these shield bugs emit toxic alkaloids. These alkaloids can be emitted when the bug is handled by humans as well. These chemicals are also responsible to the 'stinkiness' of the stink bug. They also have strength in numbers. They line up resembling a longer insect (like a caterpillar) to confuse the predators. The adult has the colouring of the seed pod. It camouflages itself from the predators, contrary to the nymphs which stand out.
Description of Green Shield Backed Bug
Eggs: These hatched eggs are typical of hemiptera eggs. They have pearlescent shine and a neatly cut circular cap from which the nymph has emerged. It was found on the pod of the Red-Eyed Wattle.
Early Instar nymphs: These are tiny, about 2 cms in length. They closely resemble the red eyed wattle seeds. They have dark dark centre with an encircling red pattern. They are highly iridescent.
4 to 5th Instar nymphs: (given the progression of the wing bud and the 3 segment antennae). These nymphs are 2 - 3 cms in length, much bigger than the seed. They have a red and green iridescent pattern.
Just hatched adult: Immdediately after ecdysis, the adult is pink in colour. It has a smooth body and doesn't use its wings. It was noticed that the adult crawled out of the shell, rather than flying out. As they grow, the colour of the adult body changes. The pink gradually becomes brown. It develops green metallic patches on the body which shine with the light. The colour is very similar to the seed pod of the red-eyed wattle, offering it camouflage and protection from predators. The adults are shy, slow moving and were not seen flying at all.
The adults have a simple eye, one red dot above each of the compound eyes.
Relationship between Red-Eyed Wattle and Green Shield Backed Bug
Red-Eyed Wattle has dry twisted pods within which lie glossy black seeds encircled by two folds of a large orange to bright red fleshy stalk-like structure. The black seed looks like an eye and the surrounding orange-red aril looks like a stalk, giving it the name Red-Eyed Acacia and the botanical name cyclops (stalk eyed).The seeds attract ants and birds. Birds like Honey-eaters and Wattle Birds feed on the seed, digesting the red aril and excreting the black seed which helps in dispersion of the seed and propagation of the plant. The interaction with ants is one of the most important mutualistic mechanisms for seed dispersal. Ants carry the seed with the encircling aril into their underground nests. The aril is nutritious but the ant cannot pierce the hard seed. The seeds are cast away, sometimes burst out of the nests during bush fires, helping the dispersal of the seed and propagation of the plant. This process is called Myrmecochory.
Red-Eyed Wattle is one of the known host plants for Green Shield Backed Bug. The nymphs and adults feed on the plant. Their piercing mouth parts are strong enough to penetrate the hard seed. The nymphs of the Green Shield Backed Bug resemble the seed and almost indistinguishable from the seeds unless examined closely. This a mimicry model. The insect nymph is at risk of predation from birds due to its bright colour. This has probably been exploited by the plant which mimics the insect to get the attention of birds for seed dispersal. Hence, the nymph may be the model and the seed may be the mimic.
The bugs have evolved to protect themselves. In order to deter the predators, these shield bugs emit toxic alkaloids. These alkaloids can be emitted when the bug is handled by humans as well. These chemicals are also responsible to the 'stinkiness' of the stink bug. They also have strength in numbers. They line up resembling a longer insect (like a caterpillar) to confuse the predators. The adult has the colouring of the seed pod. It camouflages itself from the predators, contrary to the nymphs which stand out.
Description of Green Shield Backed Bug
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Life Cycle of Coleotichus costatus
Top left: Eggs hatched
Top right: Early instar nymphs
Bottom left: 4 or 5th instar nymph
Bottom centre: ecdysis nymph to an adult
Bottom right: adult nymph
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Early Instar nymphs: These are tiny, about 2 cms in length. They closely resemble the red eyed wattle seeds. They have dark dark centre with an encircling red pattern. They are highly iridescent.
4 to 5th Instar nymphs: (given the progression of the wing bud and the 3 segment antennae). These nymphs are 2 - 3 cms in length, much bigger than the seed. They have a red and green iridescent pattern.
Just hatched adult: Immdediately after ecdysis, the adult is pink in colour. It has a smooth body and doesn't use its wings. It was noticed that the adult crawled out of the shell, rather than flying out. As they grow, the colour of the adult body changes. The pink gradually becomes brown. It develops green metallic patches on the body which shine with the light. The colour is very similar to the seed pod of the red-eyed wattle, offering it camouflage and protection from predators. The adults are shy, slow moving and were not seen flying at all.
The adults have a simple eye, one red dot above each of the compound eyes.
The family Scutelleridae is a family of Jewel Shield Bugs. Most Shield Bugs of this family have bright colours and metallic sheen making them one of the most attractive bugs of the Hemipterans. The famous Cotton Harlequin Bug belongs to this family. It is only found in East Coast of Australia. The West Coast has Red Jewel Bug which has different markings on the abdomen than the Green Backed Jewel Bug.
These Shield Bugs are True Bugs. They often confused with beetles (Coleoptera), which are essentially very different to the Hemipterans. A few general features of Hemiptera can be seen here.
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| Different stages of the Coleotichus costatus showing the Red Eyed Wattle seeds and seed pods. |
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| Fully grown adult |
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| Ecdysis, 5th instar nymph and adult |
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| exoskeleton after ecdysis |
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