The Carlisle Mosquito Online

Friday, June 29, 2007

Features

Biodiversity Corner

(Photo by Kay Fairweather)
Dodder

Name. The American Heritage Dictionary has two definitions for dodder; one is a noun meaning "any of various parasitic vines of the genus Cuscuta" and the other is a verb meaning "to progress in a feeble or unsteady manner." I haven't been able to discover how this vigorous vine came to be called dodder. Lots of other people too must have felt the name is inappropriate because it is also known as strangle weed, tangle-gut, devil's-guts, goldthread, pull-down, devil's-ringlet, hellbine, hairweed, angel's hair, devil's hair and witches' shoelaces. The plant used to be classified in the Convolvulus family along with bindweeds and morning glories but has lately been relegated to a family of its own. There are over 150 species of dodder, worldwide, and they differ in their degree of preference for a specific host. This one may be Cuscuta gronovii which is not very picky — it seems to attack almost any green plant in its path.

When and where found. Last fall, Mark Duffy mentioned dodder to me and said I would probably be able to see it in the Cranberry Bog this summer. On the day of the summer solstice, I spotted the tell-tale yellow patches as I walked around the bog.

Distinguishing characteristics. Most of what you see is a mess of yellow threads. It looks as if someone in a solstice ritual unraveled a ball of smooth fine yarn the color of the sun and flung it about over the other plants in the bog. Some of the threads are now firmly twisted around green host plants. Some are reaching out for additional hosts. The plant has no leaves, very tiny flowers, and most of the time no roots. The threads in the photo represent the entire plant. In the lower right corner there are two small host plants which have been attacked and wrapped by the dodder. The little nodules you can see there are the dodder flower buds.

Life cycle. Dodder starts life like any other plant — it germinates from a tiny seed and puts out a shoot. But then, having little or no chlorophyll, the shoot immediately seeks a green plant from which to steal food. It has enough food of its own in the seed to sustain its search for about ten days. When it encounters a plant, it wraps it counterclockwise a couple of times, and then another strange thing happens. It determines if the potential host has suitable nutrients. If so, a secondary stimulus causes it to develop specialized structures called haustoria which tap into the host vascular tissue and suck out water and food. At this point its connection to the seed and the soil wither away.

The farmers' dodder. Farmers are not amused by stories about their dodder. While dodder does not usually kill the host, it weakens it, makes it susceptible to disease and reduces the yield of crop plants. It is also a difficult plant to eradicate. The seeds remain viable for five or more years. I found a reference to dodder on the web that summed it all up under the heading of "plants that suck."

References. Integrated pest management program, UC Davis, at www.ipm.ucdavis.edu (search for dodder); Common Wildflowers of Northeastern United States by Carol H Woodward and Harold W Rickett; Weeds in Winter by Lauren Brown; Swarthmore College Biology Dept at www.swarthmore.edu/NatSci/cpurrin1/dodder.htm.

Green Marvel moth and Goldsmith beetle

The Green Marvel moth.
Close-up of the Green Marvel's face. (Photo by Betsy Fell)
The Green Marvel moth and the Goldsmith beetle have little in common except that both are handsome night-flying insects attracted to light, and both were found by Betsy Fell in the first week of June. The Green Marvel turned up in Betsy's bathroom and the Goldsmith beetle was sitting on the welcome mat one morning at the new Mosquito office on Bedford Road.

Green Marvel. The Green Marvel moth is Agriopodes fallax. It is a member of the huge Noctuidae family of moths which includes owlets, forester, and underwings. There are nearly three thousand species of Noctuids in North America some of which are called cutworm moths because their caterpillars eat shoots of young plants often cutting the plant off at the ground — a behavior well-known to most gardeners. The gardener-friendly Green Marvel caterpillar feeds on viburnums, notably the native arrowwood species, Viburnum dentatum (which can be seen in flower now near the Maple Street bridge). The Green Marvel moth can be recognized by its green forewings with prominent black triangular markings. The wingspan is about one and a quarter inches. There is a tuft of greenish hair sticking up between the wings near the thorax. The hind wings and the underside of the moth are pale gray-brown with no distinctive marks.

Department of Defense. Noctuid moths have specialized auditory organs which may allow them to detect and evade bats. These "ears" can detect frequencies in the range of 3 to 100 kHz. Bats emit high-pitched clicks ranging up to 80kHz (well within the range detectable by the moth) and find prey in total darkness using echo-location from the clicks. Human hearing, by comparison, has its upper limit around 15 to 16 kHz.

Goldsmith beetle. This handsome scarab beetle is Cotalpa lanigera. The scarab family of beetles has over 1,400 species in North America. The Goldsmith belongs to the sub-family Rutelinae,
The brilliantly gold Goldsmith beetle
also known as the Shining Leaf Chafers, the most notorious member of which is the Japanese beetle. Despite having pestiferous relatives, Goldsmith beetles feed on the leaves of deciduous trees like catalpa, willow, aspen, and poplar, and the larvae eat rotten wood and roots. The Goldsmith beetleß is about an inch long and half an inch wide. I set this hefty beetle free at the top of the Banta-Davis Land. It flew off like a big-bellied cargo plane above the aspens. You can recognize the Goldsmith by its size, its yellow color and metallic luster. The tips of the legs and the underside of the legs are blue-green and iridescent. The belly is very hairy.

Literary connections. The Goldsmith beetle is thought by some to be the "gold bug" featured in a short story by Edgar Allen Poe: "Well!" I said after contemplating it for some minutes, "this is a strange scarabaeus, I must confess; new to me; never saw anything like it before." I said something similar when Betsy first showed me the beetle. Like Poe's beetle, this one was reluctant to show its antennae but on the other hand I wasn't moved to ask if "the two upper black spots look like eyes, eh?" because there were no such spots. I wasn't bitten and am not hunting for treasure.

References: Discovering Moths — Nighttime Jewels in Your Own Backyard by John Himmelman; Borror and Delong's Introduction to the Study of Insects by Charles A. Triplehorn and Norman F. Johnson; Lynn Scott's Lepidoptera images at www.acleris.com/dls/09281.html. Special thanks to David Kleiman at Bug Guide for his ID help; see http://bugguide.net/node/view/115880.


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