Friday, November 4, 2005
When and where seen: Marjorie Johnson found this male walkingstick on October 20 on the side of her house beside the front door. He was demonstrating typical walkingstick behavior by not walking at all. Once in a while he slowly lifted his left rear leg as if some canine gene was in need of expression. These insects are masters of disguise so you are lucky to see one at all. In the daytime, they are usually up a tree keeping very still and looking like a twig. Nighttime is when they move around to feed.
Identification: These insects are hard to mistake for something else. The body is about three inches long for a male and almost four inches for a female, and only about an eighth of an inch wide. The males have a pair of pincers called cerci at the end of the abdomen for grasping the female during mating. The males are usually brown or gray and the females brownish-green. This one was brown except for his two front legs and the "shin" segment of his other four legs, which were green. He was in the characteristic walkingstick pose with his front legs stretched out in perfect alignment with his body which made him look almost six inches long. This posture makes it look like a four-legged insect. The two antennae are very fine and as long as the long front legs. You can barely see them in the photo because they are on top of the front legs. Unlike most insects, they have no wings. And yes, they do have thick thighs.
Life cycle: The female walkingstick lays 100 to 150 eggs at the rate of about 3 a day, starting in mid-August and continuing until the weather get cold in October. She casually drops the eggs one by one as she moves about in the tree tops. In the late 1800s, when walkingsticks were very common destructive pests, they say you could hear the eggs falling like rain through the leaves onto the ground. In this part of their range, the eggs usually remain in the leaf litter for two winters before the nymphs emerge around May or June of the second spring. Further south, most eggs hatch after the first winter. The nymphs are tiny replicas of the adults. They are greenish-yellow and about a quarter inch long at first. They molt five times, gradually changing from their leafy green spring color into the gray-brown twig color of the mature adult by August.
Food chain: Adult walkingsticks eat the leaves of deciduous shrubs and trees, especially oak, wild cherry, and hazelnut. The nymphs feed on low-growing plants like sweetfern and blueberry. The walkingsticks themselves are food for crows, robins and other birds. The main defensive mechanism is camouflage but they can also squirt a nasty substance from glands in the thorax. The two-striped walkingstick, a creature of the southeastern U.S., is noted for this behavior. The substance is harmful to humans if they get it in their eyes.
References: BugGuide.net is a good resource for identifying insects. You can send in photos and request an ID. The Northern Walkingstick page is at http://bugguide.net/node/view/34736; Louis F. Wilson of the USDA Forest Service, Forest Insect and Disease Leaflet 82; G.R. Nielsen, University of Vermont Entomology Leaflet # 249.
Submissions for the Biodiversity Corner are encouraged from everyone. The only requirements are that it exists in the wild and was seen in Carlisle. Send a photo and some field notes to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to firstname.lastname@example.org.
© 2005 The Carlisle Mosquito