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Soda soother
The last word– on sap from the leaves. The sap is rich in sugars but poor in protein. What protein it does contain is extracted by the insect’s gut, but most of the rest of the sap is excreted, coating the leaves on which the insects feed with honeydew. Some ant species actually farm aphids for their honeydew, collecting and carrying the aphids to suitable plants. When stimulated, the aphids excrete a droplet of honeydew which the ants feed on. The relationship is mutually beneficial: in return, the ants keep any aphid predators at bay. Terence Hollingworth Blagnac, France
PLANT DEPRESSION When I was growing up in Luanda, Angola, I remember a peculiar bush. When you touched it, the area where contact was made wilted immediately, with all the leaves drooping. This lasted for only 2 or 3 minutes, after which the leaves slowly returned to normal. Does anyone know the name of this bush and why it behaves in this way? (Continued)
G My botanist father offers another theory as to why Mimosa pudica, the drooping plant your correspondent observed, behaves like this: the ploy discourages herbivores. If a herbivore starts chomping at the leaves and immediately the plant starts to wilt, pretty soon it will look rather unappetising. Presumably a lush bush appears to contain more nutrients than one that is wilting, so the herbivore moves on to lusher-looking plants instead. This seems a rather neat defence mechanism. Chris Wright Hampton East, Victoria, Australia
FLIGHT PATH There is a tree outside my window that is frequented by bees. Any time I look out there are at least a few bees flying from leaf to leaf, and stopping to walk around the leaves they land on (see Photo). I’ve seen individual bees continue this behaviour for a while. Why are they doing this?
G The insect pictured appears to be a social wasp (or yellow jacket as it is Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
known in the US) rather than a bee. The foliage the wasp is sitting on is that of the tulip tree, Liriodendron tulipifera. I suspect this particular tree is infested with a pale green aphid, Illinoia liriodendri, which is a common pest on that plant. Heavy infestations build up during the summer and the foliage becomes increasingly sticky as a fine drizzle of sugary honeydew, excreted by the aphids, accumulates on it. Honeydew is eaten by a wide range of insects,
“Ants farm aphids for honeydew, collecting and carrying aphids to suitable plants” including wasps, flies and sometimes bees. The wasps you saw will have been tucking into the honeydew. The tulip-tree aphid is a North American species that has recently become established in the UK. Since New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.newscientist.com/lastword.ns (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
it was first found here in 2004 in the London area, it has turned up in a number of places in southern England and south Wales. Andrew Halstead Principal Entomologist Royal Horticultural Society Wisley, Surrey, UK G This photograph is of a wasp, not a bee. The most likely explanation is that the wasps are attracted by honeydew, though it is conceivable that they also come to drink droplets of water on the leaves. Wasps are normally carnivorous, but in the autumn the colonies break up and the nests are abandoned, leaving the wasps to fend for themselves. It is at this time especially that they are attracted by sugary liquids, such as those found in fruit, jam and honeydew. Honeydew is excreted by aphids and plant hoppers whose piercing mouthparts enable them to feed
THIS WEEK’S QUESTIONS Eye level The eye views images upside-down in the manner of a camera lens, but our brains reinterpret this input to allow us to see things the correct way up. Have there been any examples of damage to this part of the brain, causing people to see the world upside down? How does this happen, is the brain able to compensate and if so, how? Kel Gladesville, New South Wales, Australia Soda soother Whenever I burn myself, I use my grandmother’s old remedy to help relieve the pain and cool the wound: bicarbonate of soda, mixed with a little water and applied directly to the affected area. It works, but how? Alexandra Winter Dundee, UK
How to Fossilise Your Hamster
The latest collection from New Scientist featuring experiments for armchair scientists Available from booksellers and at www.newscientist.com/hamster
Last Words past and present, plus questions, at www.newscientist.com/lastword
PLANT DEPRESSION When I was growing up in Luanda, Angola, I remember a peculiar bush. When you touched it, the area where contact was made wilted immediately, with all the leaves drooping. This lasted for only 2 or 3 minutes, after which the leaves slowly returned to normal. Does anyone know the name of this bush and why it behaves in this way? (Continued)
G My botanist father offers another theory as to why Mimosa pudica, the drooping plant your correspondent observed, behaves like this: the ploy discourages herbivores. If a herbivore starts chomping at the leaves and immediately the plant starts to wilt, pretty soon it will look rather unappetising. Presumably a lush bush appears to contain more nutrients than one that is wilting, so the herbivore moves on to lusher-looking plants instead. This seems a rather neat defence mechanism. Chris Wright Hampton East, Victoria, Australia
FLIGHT PATH There is a tree outside my window that is frequented by bees. Any time I look out there are at least a few bees flying from leaf to leaf, and stopping to walk around the leaves they land on (see Photo). I’ve seen individual bees continue this behaviour for a while. Why are they doing this?
G The insect pictured appears to be a social wasp (or yellow jacket as it is Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
known in the US) rather than a bee. The foliage the wasp is sitting on is that of the tulip tree, Liriodendron tulipifera. I suspect this particular tree is infested with a pale green aphid, Illinoia liriodendri, which is a common pest on that plant. Heavy infestations build up during the summer and the foliage becomes increasingly sticky as a fine drizzle of sugary honeydew, excreted by the aphids, accumulates on it. Honeydew is eaten by a wide range of insects,
“Ants farm aphids for honeydew, collecting and carrying aphids to suitable plants” including wasps, flies and sometimes bees. The wasps you saw will have been tucking into the honeydew. The tulip-tree aphid is a North American species that has recently become established in the UK. Since New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.newscientist.com/lastword.ns (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
it was first found here in 2004 in the London area, it has turned up in a number of places in southern England and south Wales. Andrew Halstead Principal Entomologist Royal Horticultural Society Wisley, Surrey, UK G This photograph is of a wasp, not a bee. The most likely explanation is that the wasps are attracted by honeydew, though it is conceivable that they also come to drink droplets of water on the leaves. Wasps are normally carnivorous, but in the autumn the colonies break up and the nests are abandoned, leaving the wasps to fend for themselves. It is at this time especially that they are attracted by sugary liquids, such as those found in fruit, jam and honeydew. Honeydew is excreted by aphids and plant hoppers whose piercing mouthparts enable them to feed
THIS WEEK’S QUESTIONS Eye level The eye views images upside-down in the manner of a camera lens, but our brains reinterpret this input to allow us to see things the correct way up. Have there been any examples of damage to this part of the brain, causing people to see the world upside down? How does this happen, is the brain able to compensate and if so, how? Kel Gladesville, New South Wales, Australia Soda soother Whenever I burn myself, I use my grandmother’s old remedy to help relieve the pain and cool the wound: bicarbonate of soda, mixed with a little water and applied directly to the affected area. It works, but how? Alexandra Winter Dundee, UK
How to Fossilise Your Hamster
The latest collection from New Scientist featuring experiments for armchair scientists Available from booksellers and at www.newscientist.com/hamster
Last Words past and present, plus questions, at www.newscientist.com/lastword