Cover art by Gerald McConnell
"In an overpopulated world seeking living room in the jungles, the International Ecological Organization was systematically exterminating the voracious insects which made these areas uninhabitable. Using deadly foamal bombs and newly developed vibration weapons, men like Joao Martinho and his co-workers fought to clear the green hell on the Mato Grosso.
But somehow those areas which had been completely cleared were becoming reinfested. Tales were coming out from the jungles... of mutated insects that have grown to incredible sizes and able to produce deadly toxins... of insects who seem to be men, but whose eyes gleamed with chitinous sheen of insects."
The Green Brain, Frank Herbert, Ace Books © 1966