Clown Bug - Amorbus sp.
Family Coreidae
This page contains pictures and information about Clown Bugs that we found in the Brisbane area, Queensland, Australia.
- length 22mm
There are many common names for the Clown Bugs. They are also known as Coreid Bugs, Gum Tree Bugs, Sap Sucking Bugs or Squash Bugs. The adults are reddish brown in colour, with strong and spiny hind legs. There are many veins on their forewings, with yellow on the wing covers and a short spine on each shoulder. Their antennae are four segmented. Their bodies are long and thin with greenish-yellow to brown colour on the bottom. They are slow moving. When disturbed, they move to other side of the leaf.
In early summer, we can find many them feeding on the young leaves and new tips of Gum trees. We can find different stages of their nymphs feeding on the same trees. They are known to produce smelly defensive liquids when disturbed. We never have this experience from them. Every time we approach them we do it very gently. And they seem not so aggressive as another bugs that we found, the Bronze Orange Bugs, which ejected the smelly liquid to us even we are half a meter away.
The second picture shows an adult with defected wings. The reason of the defect is unknown. We can see the hind wings and the abdomen colour pattern, which is dark bands on orange colour, a warning pattern shown when wings are opened.
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- The small hole between its hind leg and middle leg, is the scent-gland outlet, from which the bug ejects the smelly liquid. The other holes on its abdomen are the spiracles where air enter the insect body for respiration.
- The adult of Clown Bug and the Eucalyptus Tip Bug are look similar, both of them can be found on Gum tree, although their nymphs are look quite different.
- One thing we noticed is that the bugs have spiny strong hind legs. We quite often found the bug that one of their hind leg is missing. Their hind legs may be used for avoid predators or to fright with another male. We have the discussions below.
- Eggs are laid singly on the leaf surface of shoot tip, several eggs may be laid close together.
- After hatching from eggs, Clown Bugs have five immature stages. Different stages instars can be found on the same Gum tree in early summer. For this species, even in the same instars stage, the bugs may have different colourful patterns.
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- Nymphs 1st instars, body length 8mm
- Nymphs can be found feeding in clusters on young shoots. After hatching from eggs, the 1st instars all stay at the new shot of the gum tree and start feeding. They have powerful sucking mouthparts, or stylets, which they insert into the plant to suck the sap. We noticed that on the gum tree there are some wilted young shoots. Otherwise the trees are healthy and seems not affected by those bugs.
- 2nd instars, body length 10mm The different colour 3rd instars, body length 15mm
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- Three different colours of 4th instars, body length 18mm
- Three different colours of last instars, body length 20mm
- Sometimes we can find the dark blue colour as well. The second picture show a blue nymph become black after moulting.
- We can easily see how the wing buds develop in their different instars stage.
- There is one generation per year. All of them are colourful with black, blue and orange colours. However, their colour patterns are different in different instars stages.
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- The second picture shows the mating couple, from them we can tell their male and female are looked the same and about the same size. The picture shows one bug with its wings broken. Reason is unknown, anyways, we can see the bright orange colour and black strips on the top of its abdomen.
Why the Clown Bugs have the strong hind legs?
Some species in Family Coreidae, including the Clown Bugs, have their hind legs expanded and somewhat leaf-like, and some of them are commonly called Leaf Footed Bugs. The bugs cannot jump like grasshoppers. They do not use their legs to catch other insects like preying mantids. Their legs seems not effective as a defence weapon. Why the bugs have their strong hind legs?
- We sometimes found the male bugs standing on the top of a small plant with one hind leg extended. In the second pictures, one of the the bug's hind leg is missing. It did not change it posture even we disturbed.
From our observations, we believe the bugs' strong hind legs is the result of sexual selection. The females choose their mates with stronger hind legs. The males fright with each other with their hind legs.
We have put two male Clown Bugs together, sometimes they fright with each other. They hold each other with the front and middle legs, use their hind legs try to cut the others hind legs. If we inspect carefully, we can see that the front part of their hind leg is like a saw and the middle parts of the hind leg form a cutter. We do see a bugs broken his hind legs after frighting. And the fright was end soon after one loss his hind leg.
We can predict that a male bug will have the stronger hind legs. By checking with a number of mating pair, we found that this is true. And we learn how to tell the gender of a Clown Bugs by looking at its hind legs.
This explain why sometimes we can see a Clown Bugs setting on the plant tip with its hind legs fully extend outwards. This is a male advertising his hind legs are so strong, or at least have not been broken. The strong and well shaped hind legs are used as the sign of fitness by the female bugs.
This also explain for some species, their hind legs are over emphasised as board leaf-like.
This should predict a female will only mate with a male with two good hind legs. We have observed many mating pairs but cannot have conclusion yet. We do sometimes find mating pair with single-hind-leg male. We need more observations on this.
