The winter rainfall region of the Western Cape Province is often regarded as a climatic barrier to the southward range expansion of insects. However, the availability of suitable food is usually the critical factor enabling migrants to settle, temporarily or permanently, and allowing increase in insect numbers in a biome. Own observations and the literature indicate an array of lepidopterous insects that, by switching to endemic or to introduced foodplants, have become established in the Western Cape. Some alien insects have likewise established themselves on exotic foodplants, which enabled the insects to expand their range in this region and to invade biomes to the north.
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