Why did Zompro's discovery lead to the creation of a new insect order?

Thousands of new species are discovered every year, and many of these new-to-science critters are insects. But almost invariably these newly found species fit into one of the roughly 30 insect orders (I say roughly because the ordinal level taxonomy of some groups is still debated). Discovering a species that requires creation of a new order is a much more surprising event.

In 2001, Oliver Zompro received a 45 million year old insect specimen preserved in amber that stumped him. It showed characteristics of several different orders (including the Orthoptera, Mantodea and Phasmatodea), but he couldn't definitively place it in a single order. He eventually found similar specimens in a museum collection, and after leading an expedition to Namibia, a group of entomologists found several live specimens. By examining the anatomy of these "Gladiators," as they came to be known, Zompro and his colleagues decided that the insects were physiologically unique enough to warrant the creation of a new insect order. They named the group Mantophasmatodea, a combination of the ordinal names Mantodea (the praying mantids) and Phasmatodea (the walking sticks).

What specifically was so different about Mantophasmatodea that they could not be lumped into a pre-existing insect order? Zompro et. al concluded that the insects resembled the other Orthopteroid insects (a grouping including the orders Orthoptera, Mantodea, Phasmatodea and others), but had characteristics that prevented them from falling into any one described order.

Despite looking vaguely walking stick like (Order Phasmatodea), the Mantophasmatodea differ in that they have a hypognathous (downward pointing) head, they lack the defensive chemical releasing glands of Phasmatodea, there are differences in the female genitalia and the Mantophasmatodea have a separation between the sternites (hard plates on the ventral, or belly, side) or the thorax and abdomen.

Mantophasmatodea differs from Mantodea (the mantids) and the similar orders Isoptera (termites) and Blattodea (cockroaches) again by differences in the female genitalia and also the structure of the internal head "skeleton" (the tentorium) and the central ganglion in the abdomen.

While many strange and wingless Orthoptera (grasshoppers, crickets and katydids) exist, the Mantophasmatodea were excluded from this group because the structure of the pronotum (the first segment of the thorax) differed from all known Orthoptera. Again, differences in the female genitalia also provided evidence against placing the new species in the order Orthoptera.

After carefully scrutinizing the anatomy of their specimens, Zompro and his collaborators ultimately felt confident that these creatures differed enough from the known taxa to justify placing them in their own order and family (Order Mantophasmatodea, Family Mantophasmida). They separated the specimens into two species, which you can read more about if you dive into the paper referenced below. However, Zompro’s conclusions are hardly final. As genetic techniques become more available and affordable, researchers have been exploring the genetic similarities and differences between groups of insects to determine their evolutionary relatedness. While molecular evidence can solidify the relationships determined using phenotypic (physical) traits, in many cases it disputes these findings and suggests alternative organizations to the tree of life. Since Zompro’s discovery, other entomologists have argued to combine the Mantophasmatodea with another rare insect order the Grylloblattodea. It may take years of research and discussion before the scientific community comes to a consensus.

Adis J, O Zompro, E Moombolah-Goagoses and E Marais (2002). Gladiators: A New Order of Insect- A Six-legged discovery in Africa stuns entomologists and solves a mystery in amber. Scientific American, 287, no 5: 60

Klass, K. D., Zompro, O., Kristensen, N. P., & Adis, J. (2002). Mantophasmatodea: a new insect order with extant members in the Afrotropics. Science, 296(5572), 1456-1459.

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