By Patrick Clinton

I remember, as a lad, counting cricket chirps to come up with the temperature, but I've forgotten the formula. Can you help?
Dan Boles, Revelstoke, British Columbia

Count the chirps over a 13-second period and add 40. That'll give the temperature in degrees Fahrenheit, give or take a bit. The only trick is that the formula works for just one species: the snowy tree cricket, Oecanthus fultoni.

Luckily, though, snowy tree crickets are found throughout most of North America. (In the West, there's a related species with a slightly faster chirp; in the Southeast, you're out of luck.) To find them, go out in the evening, starting in mid-July, and listen for what University of Florida entomologist Tom Walker calls "a low-pitched melodious chirp" like you might hear in night scenes on TV westerns. Walker should know: He named the species back in the 1960s.

"All crickets are pretty good thermometers," Walker explains. "They rub their wings at a rate directly proportional to the temperature." It's just that snowy tree crickets are more accurate than most; their chirps are slow enough to count, and they synchronize their singing, so you don't have to struggle to pick out a pattern from the surrounding din. Nature goes to a lot of trouble so you can amaze your friends. Be grateful.

When lightning hits water, how come the fish aren't electrocuted?
J. T. Stanton, Princeton, New Jersey

They are electrocuted. You're just too busy scrambling from the water to see it. As lightning expert Martin A. Uman puts it, when a bolt strikes a river or lake, all the fish within a few yards "come up dead, their little mouths pointing toward the sky as if in prayer."

Fish don't seem to have any special tolerance for high voltage. "Electric eels kill their prey by shocking them," notes Uman. "Some people even go fishing that way. They'll put high voltage things in the water and just scoop 'em up."

What purpose do male nipples serve?
Rolf Spencer, Norfolk, Virginia

If you're asking, "what is the evolutionary advantage?" the answer is probably none. You got your nipples in your first few months as a fetus, back when you were anatomically indistinguishable from a little girl. At about 14 weeks, hormones kicked in and caused you to develop the anatomy you know and love today. The nipples stayed, though. It would be too much trouble to suppress them, and besides, they don't do any harm.

Actually, there's no compelling reason why males can't give milk. Men are equipped with small mammary glands and ducts; all that's missing are the hormones to make them work. But there are certain rare hormonal imbalances that are known to enlarge male mammary glands, and there have even been a few reported cases of illnesses that caused men to lactate.

What about other mammals? In July 1992 a team of biologists working in Malaysia discovered that male Dayak fruit bats were producing milk, possibly to nurse their young. (Noticing that the male nipples were unusually large, the biologists gave them a little squeeze--and voilà.) It is the first case of male lactation ever documented in the wild. The team returns to Malaysia this fall, and we can only hope for answers to the burning question: Are Dayak fruit bats suffering from some kind of endocrine dysfunction--or are they just real family-oriented guys?

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