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Time to think
The back pages Almost the last word Are tortoises smart, or do they just live a long time?
Nettle effect How is it that stinging nettles don’t seem to affect my dog’s sensitive nose and ears or his relatively fur-free belly while I respond rapidly with a very painful skin rash?
Pamela Manfield Monmouth, UK A friend recently told me that he hasn’t felt nettle stings since a boyhood experience. At the age of 6, riding his new bicycle while wearing shorts and a T-shirt, he overbalanced into a patch of nettles and was badly stung all over his body. Since then, he hasn’t had a problem with them. Perhaps it is the same for dogs. Dogs probably are shielded from stings for the most part, but can feel them. A recent article in Veterinary Record Case Reports (DOI: 10.1136/ vetreccr-2018-000672) describes two gun dogs that were treated for suspected toxic effects from sustained exposure to nettles – Ed
Hourglass figure Why do wasps have such a narrow waist? What could be the advantage of having such a narrow join between thorax and abdomen, which seems like a very weak point?
David Muir Edinburgh, UK Key to the evolution of certain insects was a change from feeding 54 | New Scientist | 23 November 2019
AMMIT/ALAMY STOCK PHOTO
Fiona Hussey Aylesbury, Buckinghamshire, UK Nettles are covered in tiny, hair-like structures called trichomes with fragile ends that break off when touched. The ends act like needles, injecting chemicals that cause irritation and pain. The outer layer of skin on a dog’s nose is very thick, so I suspect that the trichomes are too delicate to penetrate it. The rest of the dog’s body has hair, and even though the ears and belly have much less hair than elsewhere, it probably still provides protection.
shorts when it was just 21°C. Obviously, I had acclimatised to the local weather. Is this a psychological or physiological process? Do any changes occur in the body?
This week’s new questions Time to think Are longer-lived animals such as turtles or tortoises typically more intelligent than those with shorter lifespans? Deborah Hartstein, Sydney, Australia Mind fuel How many calories go on running the brain? Could I burn more calories by trying to do lots of difficult mental arithmetic or solving the New Scientist cryptic crossword? Could I actually think myself thinner? Thomas Reid, Dundee, UK
on plants to laying eggs on or in the bodies of other arthropods. The eggs hatch and the larvae eat their host from the inside, eventually killing them. Around 250 million years ago, at the start of the Triassic period, a species of insect evolved to have a narrow waist, called a petiole. This adaptation allowed greater flexibility and manoeuvrability of the ovipositor, the tubular structure on the female’s rear used to deposit eggs. This insect was the last common ancestor of bees, wasps and ants. In some families of Apocrita, the wasp-waisted insects, the ovipositor has morphed over time into a stinger – as lots of us have discovered to our cost. Hazel Russman London, UK Wasps and bees have a narrow section joining their thorax to their abdomen, so they can curl their abdomens under to sting you while resting on your skin.
Dan O’Donovan, Solihull, West Midlands, UK The waist is narrow for flexibility. This area needs to act like a hinge, but unlike with a finger joint in humans, it isn’t surrounded by flexible skin and flesh. Instead, it has a hard outer casing and a thin membrane that can flex only a little. If this hinge were thicker, the membrane would have to flex further and more quickly. The joint is only as wide as it needs to be for itself, nerves and other plumbing.
Getting used to it I grew up in Perth, Western Australia, where summer days are often in the high 30°Cs. I found this warm, but not too hot. But after a year living in the UK, I was wearing
Neil Holmes Bromsgrove, Worcestershire, UK Acclimatisation will be a factor, but differences in relative humidity of the air are probably more important. In warm weather, the cooling effect of the evaporation of sweat from the skin is vitally important. When the air temperature in Perth is in the high 30°Cs, the relative humidity is usually very low, often about 40 per cent or lower. This allows sweat to readily evaporate from the skin, keeping the body comfortable. The air in the UK in summer is usually more humid. At 21°C and a relative humidity of 70 per cent, there will be less evaporation of sweat from the skin and so less heat loss. So the body will feel comfortable at this lower temperature. Eddy Richards Allanton, Scottish Borders, UK When I moved to Kenya, I experienced the same adaptation, but in reverse. After a few months, I started to put on a jumper when the temperature dropped below about 24°C. Returning to the UK was a bit of a shock, because it was snowing at the time, but I rapidly reacclimatised. However, even 30 years later, I still find high temperatures perfectly pleasant. This makes me think that the effect is psychological and is a reaction to changes in the typical temperature locally. ❚
Want to send us a question or answer?
Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms
Nettle effect How is it that stinging nettles don’t seem to affect my dog’s sensitive nose and ears or his relatively fur-free belly while I respond rapidly with a very painful skin rash?
Pamela Manfield Monmouth, UK A friend recently told me that he hasn’t felt nettle stings since a boyhood experience. At the age of 6, riding his new bicycle while wearing shorts and a T-shirt, he overbalanced into a patch of nettles and was badly stung all over his body. Since then, he hasn’t had a problem with them. Perhaps it is the same for dogs. Dogs probably are shielded from stings for the most part, but can feel them. A recent article in Veterinary Record Case Reports (DOI: 10.1136/ vetreccr-2018-000672) describes two gun dogs that were treated for suspected toxic effects from sustained exposure to nettles – Ed
Hourglass figure Why do wasps have such a narrow waist? What could be the advantage of having such a narrow join between thorax and abdomen, which seems like a very weak point?
David Muir Edinburgh, UK Key to the evolution of certain insects was a change from feeding 54 | New Scientist | 23 November 2019
AMMIT/ALAMY STOCK PHOTO
Fiona Hussey Aylesbury, Buckinghamshire, UK Nettles are covered in tiny, hair-like structures called trichomes with fragile ends that break off when touched. The ends act like needles, injecting chemicals that cause irritation and pain. The outer layer of skin on a dog’s nose is very thick, so I suspect that the trichomes are too delicate to penetrate it. The rest of the dog’s body has hair, and even though the ears and belly have much less hair than elsewhere, it probably still provides protection.
shorts when it was just 21°C. Obviously, I had acclimatised to the local weather. Is this a psychological or physiological process? Do any changes occur in the body?
This week’s new questions Time to think Are longer-lived animals such as turtles or tortoises typically more intelligent than those with shorter lifespans? Deborah Hartstein, Sydney, Australia Mind fuel How many calories go on running the brain? Could I burn more calories by trying to do lots of difficult mental arithmetic or solving the New Scientist cryptic crossword? Could I actually think myself thinner? Thomas Reid, Dundee, UK
on plants to laying eggs on or in the bodies of other arthropods. The eggs hatch and the larvae eat their host from the inside, eventually killing them. Around 250 million years ago, at the start of the Triassic period, a species of insect evolved to have a narrow waist, called a petiole. This adaptation allowed greater flexibility and manoeuvrability of the ovipositor, the tubular structure on the female’s rear used to deposit eggs. This insect was the last common ancestor of bees, wasps and ants. In some families of Apocrita, the wasp-waisted insects, the ovipositor has morphed over time into a stinger – as lots of us have discovered to our cost. Hazel Russman London, UK Wasps and bees have a narrow section joining their thorax to their abdomen, so they can curl their abdomens under to sting you while resting on your skin.
Dan O’Donovan, Solihull, West Midlands, UK The waist is narrow for flexibility. This area needs to act like a hinge, but unlike with a finger joint in humans, it isn’t surrounded by flexible skin and flesh. Instead, it has a hard outer casing and a thin membrane that can flex only a little. If this hinge were thicker, the membrane would have to flex further and more quickly. The joint is only as wide as it needs to be for itself, nerves and other plumbing.
Getting used to it I grew up in Perth, Western Australia, where summer days are often in the high 30°Cs. I found this warm, but not too hot. But after a year living in the UK, I was wearing
Neil Holmes Bromsgrove, Worcestershire, UK Acclimatisation will be a factor, but differences in relative humidity of the air are probably more important. In warm weather, the cooling effect of the evaporation of sweat from the skin is vitally important. When the air temperature in Perth is in the high 30°Cs, the relative humidity is usually very low, often about 40 per cent or lower. This allows sweat to readily evaporate from the skin, keeping the body comfortable. The air in the UK in summer is usually more humid. At 21°C and a relative humidity of 70 per cent, there will be less evaporation of sweat from the skin and so less heat loss. So the body will feel comfortable at this lower temperature. Eddy Richards Allanton, Scottish Borders, UK When I moved to Kenya, I experienced the same adaptation, but in reverse. After a few months, I started to put on a jumper when the temperature dropped below about 24°C. Returning to the UK was a bit of a shock, because it was snowing at the time, but I rapidly reacclimatised. However, even 30 years later, I still find high temperatures perfectly pleasant. This makes me think that the effect is psychological and is a reaction to changes in the typical temperature locally. ❚
Want to send us a question or answer?
Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms