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The Pittosporum Shield Bug (Monteithiella humeralis) was once native to Australia but was introduced to New Zealand in the 1950’s.

The Pittosporum shield bug has been classed as a minor pest in New Zealand it is a member of the Pentatomidae family and can be found throughout Australia and New Zealand. It can be found throughout New Zealand but is most predominant in the “Auckland region around transitional facilities”.

Some of the main identifying features of the adult Pittosporum Shield Bug are similar to the Australasian green shield bug, with the difference of being brown in colour rather than green and they are also slightly smaller in size.

The lifecycle of the shield bug consists of the egg stage, then developing into nymphs and finally adults once they have reached maturity. The Pittosporum Shield Bug will typically reproduce multiple times over the Spring to Summer period. When the eggs hatch the nymphs can reproduce and lay another set of eggs during the Autumn period.

Description:

The Pittosporum Shield Bug’s identification is going to change whilst it matures from the egg stage to the nymph stage and finally the fully matured adult stage of their lifecycle.

At the egg stage of the shield bugs life cycle they can be identified by seeing the eggs in a large quantity, this is due to a greater chance of survival of the offspring, due to predators targeting these eggs as a food source. The eggs are going to be white in colour and will also be located in a cluster, the individual eggs are also going to be around 1 – 1.5mm in length.

Once the eggs have hatched they are now classed as nymphs, which are the juvenile Pittosporum Shield Bug. The nymphs are still going to be the same size as they were at the egg stage and are going to have a circular like body shape. Some of the main identifying features are going to be that they are going to remain on the same leaf that they have hatched on, also the broken egg shells are still going to remain on the leaf. They are going to have a dark brown or black colour on their abdomen. Once they have begin to grow the abdomen is going to turn into a more brown colour. Another easily identifiable feature is that they are going to contain white coloured spots running throughout the abdomen, and whilst they mature these spots are going to gradually turn into a more yellow colour.

The adult Pittosporum shield bug is going to be approximately 4mm to 9mm in length. It will also have some similarities to the un-matured nymph, with the same brown coloured abdomen and the same yellow spots. The body shape is going to remain with the same body shape as it had in the nymph stage of the lifecycle.

Distribution:

The Pittosporum shield bug was once native to Australia and was introduced into New Zealand around the 1950's to help and control Nezara viridula populations, by competing with their food source.

The pittosporum shield bug can be found throughout New Zealand with a larger population in the Auckland region.

The Pittosporum Shield Bug gets its name due to the chosen host plant being the Pittosporum species, they can also be found a variety of other habitats which includes parks, gardens and native ecosystem. The shield bug will typically feeds on the stems, leaves and any fruit tissue and seeds of unripe fruit in the area.

Life cycle:

The Pittosporum shield bug's will be observed mating around the time when the host plants of the Pittosporum species begin to show unripe fruit, this is generally going to be around Spring and until Summer time. The eggs will then be laid on the underside of the Pittosporum host plant. The mature shield bug's are going to have the ability to lay eggs around 6 to 8 times throughout this time period. This in turn means that there is going to be a variety in the levels of maturity throughout the shield bug's. Once the eggs have hatched the nymphs are going to be seen throughout all of November and up in till late April.

For the Pittosporum shield bug to reach its fully maturity it takes approximately 41 days from when the eggs where laid. And once the shield bug has reached its maturity the unripe fruit on the chosen Pittosporum host plant is going to be used as their food source.

Since the maturity time of the shield bug is relatively low they have the ability to reproduce up to 3 times from Spring till end of Summer time.

Interactions:

The Pittosporum shield bug is going to feed on their chosen host plant which is the Pittosporum plants throughout New Zealand and Australia.

The Pittosporum shield bug does have one parasite, it is called Trissolcus oenone or the native shield bug egg parasitoid. When the shield bug lays its eggs on the underside of the host plants leaf, the egg parasitoid will come and will lay its very own egg inside the shield bugs eggs. A way to be able to tell if the egg has the parasitoid inside of it is that it will begin to develop a black ring at the top of the egg. This is the parasitoid developing inside, the wasp will then hatch inside the shield bugs egg and consume the bug. When the wasp is close to full maturity a thicker black ring will present its self on the egg it will then break through the egg shell.

Further information:

Shield bugs commonly get referred to as stink bugs this is due to the shield bugs having a specific gland that produces a bad smelling liquid. This gland is located by the thorax and the first and second pair of legs. This bad smelling liquid is used as a defensive strategy to try and scare off any predators.