Monday, September 29, 2014

A Tale of Two Mantis

Carolina Mantis gravid (pregnant) with eggs.

Chinese Mantis gravid with eggs.

     "Praying" mantis have long fascinated people. The very term "mantis" comes from ancient Greek meaning "prophet" or "seer" due to the way they hold their legs in prayer-like fashion. Most folks know that a more appropriate name would be "preying" mantis because of their predatory nature.
     All mantis have a unique ability to turn their heads around much more than other insects. They are said to be the only insects that can look over their shoulders. Perhaps this along with their religious pose, triangular heads, and large eyes endear them to people as well. There are 20 species of mantis in North America. Unfortunately, of the two we commonly see around here, the most likely one we encounter is the non-native Chinese Mantis (Tenodera aridifolia). Our native Carolina Mantis (Stagmomantis carolina) is no longer seen as often any more, especially near cities.
     There are some distinct differences between the two, at least once they are full grown. Carolina Mantis are smaller, the flightless females (which are always bigger than males in  mantis) being under 3" long. Chinese Mantis are larger, the females getting to about 4". Chinese Mantis also have wings that extend beyond their abdomen, while the female Carolina Mantis have wings that only extend part way along the back (see photos, though doesn't hold as true for males). The Chinese Mantis also usually has a light colored line along the bottom edge of its wings that the other often lacks (especially if they are green or brown in color). The egg cases (called "ootheca") also differ, with the Carolina having a long egg case while the Chinese has an oblong one (see photos below). Both species can vary widely in color, though the Chinese Mantis tend to be green rather than the other colors of grey or brown. 

Chinese Mantis egg case (ootheca)
Carolina Mantis egg case (ootheca)











     Various mantis were introduced into North America because of their purported value as beneficial insects that feed on pest species. The Chinese Mantis for example was first released in 1896 and are now by far our most common species. Mantis unfortunately are not very good as biological control agents. First of all, you can not make them eat what you target them to prey on. They will go for the easiest food item they can skewer with their raptorial spiny legs. They are just as likely to eat pollinators or other beneficial insects as pest species. Some studies even point out that Chinese Mantis grow larger and produce more eggs if they consume pollen as part of their diet, especially for females that are gravid full of eggs. It is no coincidence then that we often find large Chinese Mantis perched on flowering plants and eating the pollen covered pollinators that visit the flowers.


A Chinese Mantis feeds on a pollinator off a goldenrod bloom.

     Mantis are also cannibalistic, so you never have enough of them around to make much of an impact on pest species. Since big mantis eat little mantis, our smaller native Carolina Mantis are becoming more and more scarce as more gardeners introduce Chinese Mantis into their gardens in the mistaken intention of using them as biological controls. It doesn't help that a typical Carolina ootheca produces about 50 eggs, while the Chinese might produce 350 eggs.
     Here's a video of one feasting on a bumblebee perched atop goldenrod:
                    https://www.youtube.com/watch?v=X1jIR9lXdOs


Carolina Mantis, gravid and showing a color variation. Note the smaller size as compared to the Chinese Mantis also pictured on my hand in the photo above.

     As already mentioned, mantis are cannibalistic and will eat anything smaller than themselves (and sometimes they go after larger prey which account for stories of Chinese Mantis catching small hummingbirds, lizards, frogs, and even mice). This makes mating a dangerous prospect for the smaller males. Often times they are eaten in the process, losing their heads first. They have evolved however to be able to continue to mate even if headless. Some theorize that the extra large meal helps the female to produce even more eggs, perhaps a last sacrifice by the father. Finding a headless mantis this time of year is usually a sign of these reproductive activities.
     Even if mantis survive mating, find plenty of food, and/or are taken indoors, their days are numbered. Regardless of circumstances, they do not survive much longer than late November. They last a single season, eating and being eaten. There is so much that fascinates about these creatures (I didn't go into how they develop a single ear between their legs, the only creatures in the world with a solitary ear). I have fond memories of the many I raised as a kid and others I watched hunting in meadows, or them watching me over their shoulders like only mantis can do.

4 comments:

  1. Thanks for the great pictures and telling about the Mantis. I am wondering where you found the Carolina Mantis if they don't come near cities?

    ReplyDelete
  2. Where there is enough cover and places to hide they can manage to survive, just no where near as plentiful as the Chinese mantis, especially near urban areas. I found the one pictured and the egg mass near one of our Natural Resource Conservation Areas in Arlington County, VA, the Barcroft meadow. Thanks.

    ReplyDelete
  3. New Diet Taps into Innovative Concept to Help Dieters Lose 15 Pounds in Just 21 Days!

    ReplyDelete