WOOD-EATING COCKROACHES INVADE VIRGINIA

By Arthur V. Evans

Just kidding. Wood-eating cockroaches have really been here in the Commonwealth all along. But they only eat really rotten wood, so they pose no threat to buildings or furniture. Let’s start at the beginning.

A few years ago, while conducting an insect survey in Shenandoah National Park, I pulled apart a very moist, rotten log to find several shiny black cockroaches over an inch long living in flattened tunnels apparently chewed out of the wood. With chunky, wingless bodies, and thick spiny legs, they resembled somewhat stunted versions of Madagascan hissing cockroaches, popular denizens of insect zoos and the occasional of pet shop.

I recognized these cockroaches immediately as the famous brown-hooded wood cockroach, a native species that has figured prominently in the scientific literature, especially over the last 10 years. Samuel Hubbard Scudder described Cryptocercus punctulatus in 1862 from a single specimen collected right here in Virginia. Draper Valley in Pulaski County, to be exact.

The brown-hooded wood cockroach, Cryptocercus punctulatus Scudder

Scudder was a noted authority not only of grasshoppers, cockroaches, and their relatives, but also of butterflies and fossil insects. He coined the term “Cryptocercus” from the Greek “krypto,” meaning to hide or conceal, and “kerkos,” or tail. This is in reference to the fact that the last three abdominal segments of Cryptocercus are hidden within a chamber created by the seventh abdominal segment.

Cryptocercus cockroaches are no ordinary cockroaches. They takes four to five years to reach maturity, mate for life, reproduce only once in their lifetime and only after they have lived as a couple for a year. Both sexes actively care for their young for up to three years. Most other cockroaches live only two or three years, are quite promiscuous, breed repeatedly, and never see their young, abandoning their eggs before they hatch.

Like termites, adult Cryptocercus chew meandering galleries in rotten logs of both coniferous and hardwood trees. The galleries consist of intersecting tunnels and arena-like chambers in which they raise their young. Females imbed egg cases, or oothecae, in the walls of the tunnels. The larvae, up to as many as 75 in a single brood, change from ivory or golden in color to progressively darker shades of reddish brown as they mature before eventually turning nearly black.

Both parents and offspring eat rotten wood and rely on bacterial and protozoan symbionts in their gut to help them metabolize their food; only termites and Cryptocerus cockroaches harbor these same specific gut symbionts. Since they come into this world without the necessary compliment of gut symbionts, Cryptocercus larvae must obtain them from special anal fluids produced by their parents, just like termites. Up to six cockroach larvae at a time will bury their heads deep within the anal chamber of an adult cockroach to suck up an elixir rich in life-giving bacteria and protozoa.

Young cockroaches grow by molting, or shedding their exoskeletons. As they molt, part of their intestinal lining is also shed, and along with it goes their gut symbionts. After each successful molt they must re-infect themselves by imbibing the anal fluids of their parents in order to metabolize wood and stay alive. By the time they reach their third or fourth larval stage, the young Cryptocercus no longer lose their gut symbionts with each molt and have become nutritionally independent of their parents. Also like termites.

Scientists have long thought that termites were offshoots of ancient cockroaches. Whether Cryptocercus cockroaches are “living fossils”  closely related to termites, or a more recently evolved line of cockroach that just happens to share an amazing number of features in common with termites is still hotly debated in the scientific literature.

Scientists eager to explore the interface of population genetics and environment, the key evolutionary forces that drive the development of new adaptations and speciation, find these cockroaches elegant research subjects. After all, they are dependent on a patchy resource (rotten logs), have limited powers of dispersal, and live in close-knit family units. Plus, whether they are primitive or not, the reproductive behavior of Cryptocercus mirrors that of a king and queen termite starting a new colony, which makes them the best living models for studying the development of social behavior in modern termites.

In the 1930’s two additional species of Cryptocercus were discovered in eastern Russia and western China. In 1997, comparative DNA analysis of populations in Appalachia and the Pacific Northwest produced results indicating that each population was actually a distinct species. A similar analysis of the Appalachian populations revealed a complex of four closely related species. One of the new species was named, predictably enough, after Charles Darwin (C. darwini), while another was named in honor of Jerry Garcia (C. garciai) of the Grateful Dead.

Since 1999, an additional five species have been found in East Asia, bringing the total number of species in the world to an even dozen. More species no doubt await discovery by scientists. From Draper Valley, Virginia to China, our understanding of Cryoptocercus and the light they might shed on the very dawn of termites continues to be a long, strange, yet very illuminating trip.

© 2010, A.V. Evans

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12 Responses to “WOOD-EATING COCKROACHES INVADE VIRGINIA”

  1. I’ve long been fascinated by the concept of termites being essentially derived cockroaches. It seems to make sense morphologically/behaviorally – I wonder if any molecular studies are underway that would answer which lineage of cockroaches they came from (assuming that lineage is extant still).

  2. Thanks, Art, I have a sentimental fascination with these cockroaches. Growing up in Oregon, I learned about them and collected a few specimens. Had no idea of what has transpired in their classification since then. Thank you so much for the new info!

    • Arthur Evans Says:

      Thanks Eric!

      I see that you are now back in Tucson. Maybe I will see you this summer during my visit at the end of July!

      Cheers, ART

  3. Hi Dr Evans, I just found your website and wanted to let you know how much pleasure your Inordinate Fondness book has brought me. It never leaves my nightstand and has generated many a wonderful dream in which I turn over a long and find masses of lovely brightly colored metallic beetles. As an insect-lover and avid amateur photographer, it marries my two favorite disciplines perfectly. Your blog is fantastic too.
    from a bug-lover in Pennsylvania,
    Melody

    • Arthur Evans Says:

      Melody,

      Thank you for your very kind note! It is always nice to hear from people who enjoy the book that I wrote with my good friend and colleague, Chuck Bellamy. After a long winter, I start dreaming about beetles, too! I dream in color and to genus. The beetles are the size of footballs and hang off the branches like ripe fruit. I never seem to have a jar big enough to capture them!

      I enjoyed looking reading your blog page and looking at all the wonderful images. Keep up the great work!

      Best always, ART EVANS

  4. Arthur, I found this article whilst doing a google search: I’m in QLD, Australia, and wish to know – do cockroaches eat termites here??? I wish to point out that there is an Australian cockroach.

    thanks.

  5. ….if the answer to my above question is negative…I’m led to an unanswered question on Wikipedia: “Do cockroaches eat ants?”
    Who would know the answer to this?

  6. Matthew Roseler Says:

    Greetings Dr.Evans;

    I just found what is most assuredly a cockroach walking across my bathroom floor. I toilet paper corralled it took a good look at it and then smushed and flushed. My wife was in the bathroom… I had to kill it.

    Anyway I believe it to be a female Pennsylvania Wood Cockroach (I am rather hoping that it is) as I have noticed some similarities between them and the American cockroach. As I no longer have the visual aid, and cannot remember exactly if the bottom half was dark or not, I am hoping you might shed some light on this find for me.

    This is the first one I have ever seen in our home. It did not have any wings to speak of as I could see the the segmented coverlets of its “body.” It was reddish-brown. It was in the bathroom and was wandering about in the early morning. I have checked underneath the sinks of the entire house as well as under cupboards and cabinets. I can find no other sign of them. Is there a chance that this was a lone despot that might have made it in on some fire would which gets stored in not so air tight wood box next to the wood stove? I live in Central New York State, near Keuka Lake (A Finger Lake) and am wondering if the wood cockroach that you write about lives this far North, and if not then could the Pennsylvania Wood Cockroach be a likely and logical candidate? What steps can I do to find out if this is going to be a problem and how do I prevent it?

    Thanks for your time and insight. I look forward to your response. Feel free to email me if your analytics are more lengthy than a simple blog post.

    • Sorry, but without a body or photo I am reluctant to guess as to which species of cockroach that you saw. Given your location, there are several possibilities, including both native and pest species. Try this link and see if it helps . Also, feel free to post a photo on my Facebook page and I will try to help you.

  7. Hi Dr. Evans,
    Very interesting piece you have here on wood cockroach.
    Would you mind letting me know if you think the insect I found yesterday in Catskill Mtns (NY State) is a wood roach? See link below –

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