Thursday, February 25, 2010

Prehistoric insects theme for 27th annual Insect Fear Film Festival at U of I

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The theme of this year’s Insect Fear Film Festival may be prehistoric insects, but you can rest assured you won’t learn anything about insects, prehistoric or otherwise, in the evening’s feature films, which depict people doing battle with monster-sized scorpions (not insects) and killer trilobites (not insects and long extinct).

In that light, the members of the UI Entomology Graduate Student Association I checked in with recently thought listeners might be interested to take a quick trip back through time, for a more realistic glimpse of where today’s insects come from.

Rob Mitchell, Laura Steele, Scott Shreve and Nils Cordes collaborated on this report.

[Rob M.] Insects are everywhere, and so common we barely give them a second thought when they aren’t intruding in our homes. Few people would guess that these diminutive critters have been dominating the planet since before the dinosaurs. Together with other animals like crabs, scorpions, and centipedes, insects have been on Earth for hundreds of millions of years, and they were the first pioneers to crawl onto land and fly in the air. Scientists call this group of hard-bodied animals “arthropods,” and over the eons they have taken some amazing forms, from familiar but dog-sized dragonflies to shuffling, spiny creatures whose true shapes are only the vaguest hints of fossils.

[Laura] Some insects that occur today may seem enormous, such as the giant walking sticks that reach 13 inches in length. But such creatures pale in comparison to their ancient relatives. Approximately 300 million years ago there lived a dragonfly-like insect called Meganeura, whose wingspan measured close to 30 inches. [Among the fossils on display at the IFFF will be this beautifully preserved fossil dragonfly from the Cretaceous Period of Brazil. Photo by Sam W. Heads.] Like dragonflies of today, Meganeura were predatory, and they may have even fed on small amphibians. What enabled some prehistoric insects to grow to such large sizes? Scientists think it was likely the higher levels of oxygen present in the atmosphere during that time period.

[Scott] Fossil evidence suggests that the first insects likely appeared late in the Silurian geological period, about 425 million years ago. These earliest insects probably looked most like the silverfish and springtails we see today. Insects didn’t have any wings and couldn’t fly until about 390 million years ago. Some of the first flying insects, similar in appearance to mayflies and dragonflies, had what look like a third pair of smaller wings in addition to the four wings we see today. These were called “paranotal lobes,” and they couldn’t flap or move like the normal wings.

[Nils] But even before the earliest insects, there lived a highly diverse, widely dispersed class of related creatures that must be seen to be believed, the trilobites. While trilobites were not insects at all, they were very similar to them in appearance. [Ph.D. student Scott Shreve displays a trilobite fossil from the UI Department of Entomology teaching collection that will be on display at the IFFF.] Like insects, they had a rigid outer shell and had to molt several times to grow. Trilobites had three lengthwise body segments, or lobes, which gave them their name: Tri-lob-ite. They lived under water but came in all shapes and sizes. The smallest trilobite was less than a millimeter in size, but the biggest one grew to be over two feet long. Many had hundreds of impressive-looking spikes on their backs.

While trilobites became extinct about 250 million years ago, they can still be found in the form of fossils today. Fossils of trilobites are common in the Northern U.S., and Mazon Creek, near Morris, Illinois, is a great place to start looking.

Or just come to the Insect Fear Film Festival on Saturday, where fossils of trilobites and a variety of prehistoric insects will be on display. The festival will take place at the Foellinger Auditorium on the UI campus, with festivities beginning at 6:00 p.m. and films beginning at 7:00. Further details are available on the Web at