Monday, August 13, 2007

Duckweed firetail


The park hasn't seen a drop of rain since June 21, when the rain gauge measured a measly .5". Premature acorns are jettisoning off the oaks and the stinging nettles are dropping their leaves 2 months early in protest. In a landscape of drastically altered hydrology, the lack of rainwater pooling has had detrimental effects on the summer's turtle survey. The water that sat since September is a mere memory, thanks to the adjacent landowner who tore down the beaver dam that was responsible for keeping water in the swamp this summer. And in case you were wondering, the Clean Water Act does little to nothing to protect fragile nature preserves from the needs of the farmer.

Last week, I was visited by one of my more esoteric colleagues, an entomologist who worked for the Illinois Natural Heritage program. He loves finding species new to science and will go to great lengths to get his records published. He cut his teeth on the insects of the embayment, so a visit to southeast Missouri to check out our embayment insects was in the cards this year. He had two goals in mind when he came to the park; he wanted to see the butterfly Portlandia, a pale version of the Creole Pearly Eye that lives in cane, and a damselfly called the duckweed firetail, a bright red damselfly that only perches on duckweed mats.

Anyone can imagine my colleague's disappointment when I told him that there was only one section in the entire park, entirely classified as a wetland, where duckweed mats might be found (if they hadn't dried up, too). We hiked to the small patch of water left since the destruction of the beaver dam. We looked for about 3 minutes before I found one, perched on the duckweed in all its fiery redness. My herpetologist took pictures (above) for evidence that the embayment insect persists in the park, despite the recent drainage of the swamp.

Damselflies and dragonflies belong to the order Odonata. The differences between the two are obvious: dragonflies rest with their four wings open while damselflies close their wings behind their bodies. A dragonfly's eyes generally touch one another while a damselfly's eyes are widely spaced. Dragonflies can live without standing water, but damselflies will only perch near water. Needless to say, we have many more dragonflies than damselflies these days.

Odonates breed while flying and deposit their eggs on or near water. Odonate larvae are entirely aquatic and require clean water for breeding. In fact, they are one of the bioindicators of water quality. Odonates are voracious feeders, eating everything from small fish and mosquito larvae to salamander larvae and tadpoles. Adult odonates can live for 1 to 9 months and feed entirely on insects. They are largely responsible for keeping mosquito populations in check.

The duckweed firetail larva, like many other species, emerges as an adult in the spring. The emergence is fascinating to watch--the nymph crawls out of the water, breaks open its skin along the midline and releases a winged adult. Unlike other damselflies, the duckweed firetail matures deep in the forest, rather far away from aquatic habitats. This insect is rather uncommon west of the Mississippi and has only been documented in eastern Louisiana from two sites and in Texas at one site. The adults tend to perch on duckweed simply because the larvae tend to congregate underneath. After they emerge, they stay near their nursery site until they set out for the forest for maturation.

We only saw one of the embayment damselflies last week before my colleague (who spends way too much time in the office) got overheated. I can't imagine the populations are very healthy in such an altered landscape devoid of available habitat, but maybe if it rains soon, very soon, they can hold on for at least another year.

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