Leaping Cockroaches!

That’s not a quote from a Batman Episode; it’s a new species found in only one area in South Africa.  They were discovered by accident when two entomologists were sweep-netting a meadow. 

BOHN, H., M. PICKER, K.-D. KLASS & J. COLVILLE 2010.A jumping cockroach from South Africa, Saltoblattella montistabularis, gen. nov., spec. nov. (Blattodea: Blattellidae). - Arthropod Systematics & Phylogeny, 68 (1): 53-69.

As you can see from these photos, the cockroaches have unusual hind legs that are modified for jumping, just like a grasshopper.  (The authors christened this animal the “leaproach”, although I would have lobbied for “cockhopper” myself.)

Now, I know that a lot of people don’t count roaches in their list of favorite insects.  So, a roach that can bound around like a kangaroo, which -I- think is really cool, is probably a nightmare for some.  Humans are most familiar with pest roaches, but those species only make up an estimated 1% of total roach diversity.  The rest of the 4000 species of roaches are benign, and often essential to ecosystem health.

Roaches have an amazing amount of modifications to the basic roachy body plan that let them survive in all sorts of environments.  There are diving roaches, sand-burrowing cockroaches, wood-eating roaches, and bioluminescent roaches.  Frustratingly, there is little information in the paper about why these leaproaches might have left scuttling behind for leaping.  The biggest hint is that they are found hopping around in grasslands during the day, pretty much side-by-side with grasshoppers.  Being able to jump long distances to avoid predators and find new food sources is handy for both grasshoppers and roaches.

Regular roaches can jump pretty well; the common German cockroach Blattella germanica can jump distances of 4 cm without any special leg modifications.  It’s not hard to imagine that day-active roaches that could jump a bit farther might be selected for over many generations.

cockhopper

Leaproaches are a really neat example of convergent evolution. Convergent evolution describes what happens when species that are distantly related–a grasshopper and a roach, for example–become more similar in appearance or structure because of natural selection.

Convergent evolution is the reason why a salmon, a shark, and a dolphin have similar body shapes, while they are not closely related taxonomically.  The physical environment they live in shaped their evolution in similar ways to solve similar problems–moving through an aquatic environment, in this example.

The  leaproach in this photo clearly has several body changes that are analogous with what you see on a grasshopper–primarily enlarged hind legs and big eyes.

Why not enlarged front legs? Well, if you want to go forward, the direction your eyes and other sensory organs are pointed, large jumpy front legs are not that helpful.  Hind legs help to propel you in the right direction, plus you have 4 legs you can reach out in front as you jump to grab onto passing stems of grass and hold on.

Similar environment, similar environmental constraints, and TA DA!  Leaproaches.  Neato!