Thursday, December 08, 2005

ENV: Insect Lifespans

Mike Quinn is the state invertebrate biologist for the Texas Parks & Wildlife Department. He's the one with the dynamite Texas Entomology website that has pix of the new U.S. butterflies i posted about below. I think it's largely coincidental but he's forwarded on a number of really cool things today that interest me. Another i posted below is the recovery plan announcement for some Alabama snails.

Well, here i'm relaying some intriguing info from his TX-Ento listserv. A correspondent opens with a question about life span in the genus Zopherus (that's those cool black-dotted white beetles that you often find clinging to hackberry trees. I've always called them Hackberry Borers, but the usual common name is Ironclad Beetle.

Anyway, her question is answered by Dr. Michael Merchant and then by Mike Quinn, both of whom impart some very intriguing details.

Here's the discussion (actually excerpts of the pertinent portions, with minor edits for clarity):

Thursday, December 08, 2005 1:09 PM

Hello. I have just read about the Ironclad on the TCE website.

I am particularly interested in Zopherus chilensis, which I understand is the species usually inset with jewels to become a living broach.

Do you have any information on the lifespan of Zopherus chilensis? I have been led to understand that these broaches are passed on through generations, which doesn't make sense to me. Do any beetles live that long?

Best regards,
merilyn simonds

Ms. Simonds:
I don't have much information about the longevity of Zopherus species (Z. nodulosus haldemani is the Texas variety), a.k.a. Ironclad Beetles. These insects are known to be highly resistant to desiccation, which implies that they could probably live for a pretty long time, in insect time, glued to the end of a stickpin.

If a generation means 20-30 years, however, I would say it is not possible that an insect would survive this long. Common lore is that the 17-year locust is the longest living insect, though there have been reports of longer-living insects. For example, an article in American Entomologist reported that an ant queen lived to be 14 years old, a Margarodes vitium nymph was found alive 17 years after being deposited in a collection, Yucca Moths with a 16-17 year diapause have been reported and Buprestid beetles 10-26 years old have been found in structural wood (Berenbaum, M. 1994, Bull. Entomol. Soc. Am. 40 (4):196) On the other extreme, some midge insects have a one-hour lifespan.

Oh, and by the way, importing living beetles on jewelry like this into the U.S. is considered illegal by our government. Living jewelry is interesting but not very environmentally friendly practice, as it can lead to the endangerment of rare and valuable species.

Michael Merchant, PhD, BCE
Urban Entomologist, Texas Cooperative Extension
Dallas, Texas

The life cycle of a number of insects stretches out over several years, particularly up north or in wood boring insects, but I think it is extremely rare for a non-social adult insect to live more than 12 or 18 months. . .

Dr. Burke (1976) writes that little is known of the life history of many southwestern insects, including Zopherus nodulosus haldemani. . .

Burke, H.R. 1976. The beetle, Zopherus nodulosus haldemani: Symbol of the Southwestern Entomological Society. Southwestern Entomologist, 1(3):105-106.

Under exceptional conditions, some individuals of wood-boring beetles (Cerambycidae and Buprestidae) have the longest life cycle. One Buprestis aurulenta larva emerged after 51 years. Three species of 17-year periodical cicadas, Magicicada septendecim, M. cassini, and M. septendecula, are well-known to have the longest synchronized development times in natural conditions.

Zeng, Yong. 1995. University of Florida Book of Insect Records, Chapter 12 Longest Life Cycle. University of Florida, Department of Entomology & Nematology, Gainesville, Florida. 8 May 1995 .

Mike Quinn, Austin


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