Eucalyptus Tip Bug, Clown Bug - Amorbus robustus

Family Coreidae

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

Female, body 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 orange yellow on the wing covers and a sharp angle on each shoulder. Their antennae are four segmented. Their abdomen are long and thin with greenish-yellow to brown colour on the bottom, bright orange black banded on the top, covered by wing-covers. They are slow moving. When disturbed, they move to other side of the leaf. The bug may eject smelly liquid as defence.
This is the most common Amorbus species in Brisbane. As all other bugs in this genus, they feed on shoots of Eucalyptus trees. Males have shouter hind femora and spiny hind legs. Their nymphs are variable mixed bright colours.

Male and Female

Males have shouter hind femora and spiny hind legs. 
wpe7.jpg (35112 bytes) wpe1A.jpg (45607 bytes) wpe7.jpg (34810 bytes)
DSC_2067d.jpg (78752 bytes) DSC_2737.jpg (86262 bytes) wpe17.jpg (29186 bytes)
wpe6.jpg (23775 bytes)
Mating pair                                                           Male and female
The above picture shows the mating couple, from them we can tell their male and female are looked very similar 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.


DSCN1083.JPG (91620 bytes)
Coreid eggs                                                           
After mating, female lay eggs on host plants. Eggs are laid singly on the leaf surface of shoot tip, several eggs may be laid close together. The picture above shows some Coreid eggs. We are not sure what species of coreid lays those eggs, but most coreid eggs look very similar to these, including this species.         

Five Instars Stages

Their life cycle is one generation per year. In early summer, we easily found many of them feeding on the young leaves and new shoots on different Gum trees. After hatching from eggs, Clown Bugs have five immature stages. Different stages instars are found on the same Gum tree in early summer.  They are in vary colours and patterns.
wpeE.jpg (22750 bytes) DSC_9144.jpg (89203 bytes) DSC_0827.jpg (92791 bytes)
1st instars, body length 8mm, as far as we found, all 1st instars are same colour patterns.
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. 
wpe11.jpg (19322 bytes) DSC_2257.jpg (86305 bytes)
2nd instars, body length 10mm                               
We noticed that on the gum tree there are some wilted young shoots. Otherwise the trees are healthy and seems not affected very much by those bugs.
wpe8.jpg (29703 bytes) DSC_0833.jpg (77945 bytes) wpe13.jpg (19542 bytes)  
3rd instars, body length 15mm 
Notice how the wing buds developed in different instars stage.
wpeB.jpg (23412 bytes) wpe13.jpg (23731 bytes) DSC_2787.jpg (88045 bytes)
4th instars, body length 18mm 
DSC_2720.jpg (115505 bytes) wpe11.jpg (27739 bytes) wpe15.jpg (24262 bytes)
5th or last instars, body length 20mm
The above 3rd picture show a pale blue nymph become black/yellow after moulting.
wpeA.jpg (32085 bytes) DSC_4322.jpg (96551 bytes)
There are the dark blue colour forms as well.

The Smelly Bug

They are known to produce smelly defensive liquids when disturbed. We never have this experience from them. Every time when we approach them, we do it very gently. They seem not so aggressive as another stink bugs that we found, such as the Bronze Orange Bugs, which ejected the smelly liquid to us even we are half a meter away.
wpe8.jpg (36521 bytes) DSCN0731.JPG (118295 bytes) 
Scent-gland outlet 
In the above first pictures, 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.
wpeF.jpg (28179 bytes) wpe17.jpg (27747 bytes) DSCN0073.JPG (92420 bytes)
The above first picture shows an adult with defected wings. The reason of the defect is unknown. We can see the abdomen colour pattern, which is dark bands on orange colour, a warning pattern shown when wings are opened.

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. 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?
DSC_2059d.jpg (86898 bytes) wpe6.jpg (25717 bytes) wpe8.jpg (23534 bytes)  
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.

1. Insects of Australia, CSIRO, Division of Entomology, Melbourne University Press, 2nd Edition 1991, pp 504.
2. Specimen Image Index - Insect Reference Collection Database - ICDB, Western Australian Department of Agriculture, 2006. 
3. Insects of Australia and New Zealand - R. J. Tillyard, Angus & Robertson, Ltd, Sydney, 1926, p147. 

Back to top

Up ] Wingless Coreid Bug ] Eucalyptus Tip Bug I ] Eucalyptus Tip Bug II ] [ Clown Bug ] Wilted-tip-mimicking Squash Bug ] Armoured Tip-wilter ] Crusader Bug ] Large Squash Bug ] Fruit-spotting Bug ] Cotton Plant Bug ] Horned Coreid Bug ]


See us in our Home page. Download large pictures in our Wallpaper web page. Give us comments in our Guest Book, or send email to us. A great way to support us is to buy the CD from us.  
Last updated: April 13, 2008.