Distribution
The plant is native to Central America and adjacent parts of Mexico, but has become an invasive weed in other areas.
Behavior
Ageratum has evolved an ingenious method of protecting itself from insects; it produces a precocene compound which interferes with the normal function of the corpus allatum, the organ responsible for secreting juvenile hormone. This chemical triggers the next molting cycle to prematurely develop adult structures, and can render most insects sterile if ingested in large enough quantities.
Defense
"Ageratum houstonianum" is toxic to grazing animals, causing liver lesions. It contains pyrrolizidine alkaloids.References:
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