The cockroach could be the largest in the world, at 10cm long.
A "monster" cockroach and other new insects have been discovered in the jungles of Borneo, scientists say.
An expedition of caves and cliffs, led by the Nature Conservancy, also said it saw previously unknown fish and plants.
"In just five weeks, the expedition team discovered numerous new species previously unknown to science," the conservancy's Scott Stanley said.
"Who knows what else is out there?" he added, calling for the area surveyed in East Kalimantan to be preserved.
"If something is not done soon to protect these areas, dozens of species could disappear before anyone knew they ever existed."
Borneo is one of the world's richest regions, in terms of biodiversity, but the area had no special status that might have protected it against illegal mining or logging.
The team of scientists explored four "karst" systems of limestone caves, cliffs and sinkholes in the Sangkulirang Peninsula, about 1,200km (750 miles) north-west of Indonesia's capital, Jakarta.
At 10cm (4in) long, the newly-discovered cockroach is believed to be the largest in the world.
As well as the "monster" cockroach, the scientists reported a new "micro-crab", a pure-white 6.5cm-long millipede, two new species of begonia, two new species of snail and several new types of fish, the conservancy said.