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The Mystery of the Donut's Hole

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Published on: Jan. 2, 1996

Last revision: Oct. 20, 2010

collect camel crickets for Ted's mapping purposes (10 year-olds are best; they are patient, thorough, capable of intellectual excitement, and are, generally, badly underemployed.)

I have four notebooks filled with personal observations of my captive camel crickets. Although I have witnessed many of their wooings and matings I have never seen a female feed from the male's orange gland, if that is what it is. I suspect the pronota of older males simply ruptures from the wear and tear of life on a fragile part of the insect body. For two years running I've been cross breeding camel crickets from the rim of the donut with those inside of the hole.

Last year I isolated a virgin female from my house, one of the notched pronotum population, which I'll call "holers" from now on, and let her breed once with a local male. Then, weeks later, I mated her, also just once, with a male from 20 miles distant, one from the smooth pronotal population, henceforth known as "rimmers," a resident of the rim of the donut. The reason I had to wait so long to mate her the second time is that rimmers take longer to mature than do the holers, a situation which I find interesting and perhaps significant in helping to solve the puzzle.

The female's first batch of offspring hatched out and grew up. The males had the characteristic notched pronata with the orange bulb. The second hatch, which came along much later, was about a zillion baby camel crickets. They took a much longer time to mature than did the first hatch, corroborating my observation of the rimmers in the wild. But they had a lot of trouble growing up.

The zillion rapidly decreased in number. Many died while molting from one stage to another, trapped in their old exoskeleton; some were deformed, legless. There were many monsters in the population with abnormally thickened or distorted bodies. They climbed and jumped less than their step brothers and sisters. In the end, only two females and a single male - and yes, he had a smooth pronotum - grew to sexual maturity. They mated and the females laid eggs which were fertile and young camel crickets hatched from them.

A species is defined as that population which interbreeds and produces fertile offspring, so this cross breeding indicates that these two populations are still a single species. But it also suggests something to be tested out in later experiments: the males' genes are the ones that determine whether or not the male offspring will have notched pronota with an orange bulb. In the wild where the two populations overlap they seem to be separated by differing speeds of maturity so they would, in fact, have little chance to interbreed. Could this separation in time be the isolating mechanism that allows a new species to form?

In the spring I simplified the experiment. I segregated males and females from both populations. Unfortunately the male rimmers all died or ate one another while in vulnerable molt before I could give them to mates. I'll have to catch more next year and separate the males, each to his own jar. But I was able to bring along some of the female rimmers and presented one, mature, but virgin, to a local male, a holer, who had been mature but unmated for weeks. They mated. It is August as I write this. The male has long since died at a ripe old age for his kind, but the female lives on. I have seen her lay eggs. and I hope to see them hatch and will watch to see what kind of males are among the offspring.

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