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Invertebrate: Caterpillar, Karoo

Find, identify & discuss the insects of SANParks
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Addo Elephant
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Invertebrate: Caterpillar, Karoo

Unread postby Addo Elephant » Tue Dec 11, 2007 9:41 am

Those of you who have the chance to visit Camdeboo National Park soon, or have been lucky enough to visit recently, will notice that the veld which was so green has started to turn brown.

This miraculous transformation is caused by a small (1cm long) caterpillar commonly known as the karoo "rusper" with a scientific name of Loxostege frustalis. When there has been a drought, followed by good rains, these caterpillars hatch out and proceed to consume the karoo bush, particularly concentrating on Pentzia species. They defoliate the plants, causing the veld to look brown.

They then pupate into moths about 12mm long, brown with small white spots. If you have been in a karoo town at night(or even in Addo) you will see these moths drawn to the light in their thousands.

Two generations of moth are produced a year, in the spring and then again in March-April. The moths feed on nectar of flowers.

This is a natural process that occurs in a karoo ecosystems, much like the locust outbreaks and as such, is left to run its natural course.
Megan Taplin
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Unread postby DuQues » Tue Dec 11, 2007 10:19 am

Are there any permanent changes caused? I can imagine the weaker plants not surviving such an onslaught, and that probably causes other species to have more space...
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Unread postby Addo Elephant » Tue Dec 11, 2007 3:22 pm

I don't think it would cause a whole species to become locally extinct, unless there were other factors such as climate change at work.

You could compare the effect of this caterpillar (or the brown locust which may also occur here) on the karoo ecosystem to the effect that fire has on grasslands. It rejuvenates the system. All the plant matter is reduced and the bush starts to grow again from scratch. This gives other species which may have been outcompeted before, a chance to grow again.
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Unread postby restio » Tue Dec 18, 2007 7:37 pm

Really interesting - thanks, Megan!

We stopped at Three Sisters in the Karoo on our way back from KNP, and there were thousands of moths, covering practically every surface. We wondered what they were - and I think you've us the answer! :D
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