The discovery, which is among the largest of its kind at the airport, was made after a 22-year-old man travelling from Burkina Faso via Istanbul was stopped at the South Terminal.
When officers checked his luggage they discovered tens of thousands of dried caterpillars shrink-wrapped in cellophane, which had been packed into four hessian bags. The man claimed that they were for personal consumption and that they were to be used as food.
The insects were seized by Border Force because they breach controls on the importation of products of animal origin.
Following the detection, which took place on 23 February, the man was warned by officers about the restrictions on bringing dried insects into the country. The insects will be destroyed.
Ingrid Smith, from Border Force, said: ‘This was an unusual seizure but the vigilance of our officers has stopped these dried insects from entering the UK, and possibly posing a risk to our food chain.
‘I would warn travellers not to attempt to bring any products of animal origin into the UK without a permit, as they may not have been inspected to appropriate standards and may contain diseases.’
Restrictions apply to products made from meat, dairy, fish, eggs and honey, as well as some fruit, vegetables and plants.