The discovery by Danish and German researchers is detailed in a paper appearing in Friday's issue of the journal Science.
Just three of the paperclip-sized insects are known. They have been placed in the new category "mantophasmatodea."
The insects are just under an inch long and two of the examples under study in laboratories came from tropical Africa. The two had been in museums. An additional example was found encased in amber from Europe's Baltic region.
The age of the African examples, now held for study in museums, is not known. The example in amber "is 45 million years old, but you can argue that they are surely much much older," said Klaus-Dieter Klass of the Max-Planck Institute for Limnology in Plon, Germany.
He said that when comparing characteristics of these insects with known orders the researchers found they did not fit with any other group.
They look a bit like crickets, for example, but lack the jumping hind legs that mark that order.
The scientists said that based on their stomach contents the insects appear to be carnivores.
In biology, an order is a primary classification of related animals, which is then subdivided into genera and species.
The researchers assigned one female insect from Namibia to the genus Mantophasma zephrya and a male from Tanzinia as Mantophasma solana. In addition they assigned the insect in Baltic amber, known as Raptophasma Zompro, to the Mantophasma order. That insect had previously been classified in the order Orthoptera, which also includes cockroaches, crickets and grasshoppers.
The closest relatives of the new order may be the grylloblattodea (ice-crawlers) or the phasmatodea (stick insects), but there isn't enough evidence yet to be sure, the authors say.
While several different groups of marine animals have been discovered in the last fifty years, the many insects discovered have all fit into known orders, until now. The last time a new order of insects was discovered was in 1914.
The discovery was reported by researchers at the Max-Planck Institute and University of Copenhagen, Denmark.
The new insects have jaws with three small teeth and long antennae, the scientists reported. The examples found had external sex organs indicating they were adults. They lacked wings.
By Randolph E. Schmid