The Mantasphids were a species of sapient, bioluminescent insects.
Most of the Mantasphids resembled Earth flies, but much larger. They had six legs, two sets of wings, rounded heads and elongated bodies. Their eyes and abdomens naturally glowed green.
The Mantasphid Queen was vastly different in anatomy: She had a bloated abdomen, six large legs and two smaller manipulator limbs, large compound eyes and six large antennae. She towered over humanoids and was capable of speaking. (TV: The Infinite Quest)
During the 40th century, the Mantasphids had invaded the human colony planet Myarr, needing the dung produced by the livestock. There was an all-out war on the planet, with the Mantasphids building huge hives in the forests and slaughtering the human locals.
On Volag-Noc, Ulysees Meregrass learned of the conflict from a Mantasphid who was incarcerated there. He decided to take advantage of it and made a deal to ship weapons to the Mantasphids. While making a delivery, he picked up the Tenth Doctor and Martha Jones and brought them to the Mantasphid queen. At the same time, the humans believed that the war was too far gone and were planning to destroy the Mantasphid city and everything else in a 100 mile radius. Though the Mantasphids intended to fight back, they also refused to pay Meregrass and he refused to give them the weaponry. As there was no other option, the Mantasphids agreed to the Doctor's plan that they surrender to the humans and then cooperate with them by providing their biophosphorescence as an energy source. The Doctor got in contact with the human forces and pretended to be an evil pirate that had been controlling the Mantasphids, removing them of all blame. (TV: The Infinite Quest)