Thursday, October 31, 2013

Good mantids, bad mantids

This sticklike animal with the powerful Popeye forelegs is a Carolina Mantis, Stagmomantis carolina. It's a female, and as is the case with mantids, she's a lot bigger than the male. The Carolina Mantis is our native "praying mantis" in these parts, but they're probably a lot harder to find these days than they once used to be. I made this photograph in Adams County, and southern Ohio is the only place I encounter them. I don't believe I've ever run across one in my heavily developed neck of the woods, which is Columbus, Ohio.

This is the mantid that I run across FAR more frequently than the comparatively diminutive Carolina Mantis, and I bet that's the case with you, too. It's the widespread and ubiquitous Chinese Mantis, Tenodera sinensis, a true giant of a bug. Females can be massive, and this old warrior is probably a good four inches long. I photographed her a few weeks ago on the grounds outside my office, and she's still there. The first truly cold frosty nights will take her out, but unfortunately she's probably already deposited several of her foamy brown egg cases. Each case contains hundreds of eggs, but fortunately the mortality rate is enormous and relatively few of the juveniles will make it too adulthood.

The gorgeous purple-flowered plant is Shale-barren Aster, Symphyotrichum oblongifolium, a native that has made its way into the nursery trade. It truly is a fantastic plant, and a total bug magnet. Shale-barren Aster, in this ornamental form, becomes a small bush bedecked with hundreds of blooms, and it flowers nearly to winter. Mrs. Mantis knows well the allure of these flowers for all manner of pollinating insects; that's why she lives nearly her entire adult life hiding amongst its flowers.

Chinese Mantids have an undeniable charisma, and enchant most people who encounter them. The impressive size, coupled with the formidable "praying" forelegs makes for an impressive spectacle. The animals also have a habit of watching you, cocking their pointy triangular heads to track your movements and sometimes rearing up aggressively if pushed.

As you've probably deciphered from the name, Chinese Mantids are not indigenous to the Americas; they are another in a long list of Asian imports. This species was intentionally brought to North America in the mid-1890's, ostensibly as a control for "pest" insects. In my view, the mantis itself has become the pest, and any benefits from them are far outweighed by the damage they do.

The primary issue with Chinese Mantids is that they are indiscriminate in their choice of victims. About anything that can be seized and overpowered is fair game. This includes butterflies, all manner of invaluable pollinating flies, bees, and wasps, and even prey up to the size of tree frogs and hummingbirds. I and others suspect the reason we no longer see the smaller native Carolina Mantis in many areas is due to competition with this Asian introduction.

I must admit, watching a Chinese Mantis hunt is a fascinating exercise. She's patient as can be, and just sits rigidly next to a pollinator-friendly batch of flowers. When an insect takes the bait and alights, the mantis swiftly lunges and snares the victim in an Iron Maiden death grip from which there is no escape.

While making my photos, this hapless Cabbage White butterfly, Pieris rapae, dropped in and I knew it was toast. Camera at the ready, I managed some photos of the kill. Death by mantis is not a particularly pleasant way to go. First, you're crushed in a viselike grip by spined legs, then the mantis begins methodically consuming your body, usually starting with the head. Insofar as I know, no sedating neurotoxins or anything else that can take the edge off this experience are injected - this is pure unadultered raw carnivory.

If only the Chinese Mantids would stick to other nonnative creatures such as this butterfly, most people would probably not have many problems with them. In fact, we'd probably applaud them and hail the release of mantids as a good thing - an all too rare case of an intentional "biological control" introduction that worked. But they don't, and as a consequence mantis predation is just one more threat that many of our declining species of pollinating animals face.


Avi Eitam said...

Successful biological control is not rare at all. In fact many species of exotic weeds and agricultural pests are effectively controlled by biological control agents without harming native species. While it is true that general predators had been released in the past for biological control, some of them causing considerable harm, biocontrol practitioners have learned from past mistakes. Host specificity tests are currently required on all potential biocontrol agents. Only species with narrow host ranges that will not harm endangered or beneficial species are approved for release by the USDA permit unit.

jaredmizanin said...

Cool post...I've never seen a Carolina Mantid (I live in Cuyahoga County). Question--I seem to be seeing more and more Chinese and less and less European. Am I correct in saying that we have two invasive mantid species (the European generally green with a black-and-white patch on the inner forearm?). I remember seeing those as a youngster, but nowadays it is Chinese, Chinese, Chinese.

Jim McCormac said...

Points taken, Avi, but boy, when we blew it back in the day, we really caused havoc: House Sparrows, Compsilura concinnata, Multicolored Asian Lady Beetle...

I never notice the European Mantid, Jared, although supposedly they're around. That may just be my lack of mantid ID skills, though...

Deborah Otero said...

I just found one of these on my porch any idea how I can get rid of it

MKeenanM said...

We just found one on our porch in Columbus. It actually was found in the corner of our porch last evening and when we came out this AM it was on our pillar. It creeps me out!