The insects are the Madagascar hissing cockroach and the Argentine cockroach, both banned in Australia. The seizure is the largest ever of exotic invertebrates in the country, the Australian Department of the Environment said.
"We take our job of protecting Australia's unique biodiversity and breaches of national environmental laws very seriously," a department spokesperson said.
Reptile expert Stefanie Lesser told ABC that the cockroaches are likely being sold as reptile food. The cockroaches are larger than those native to Australia, making them cost-effective for feeding reptiles because fewer are needed per feeding.
