- Email: [email protected]
Fowl play
The last word– THAT’S THE SPIRIT After painting, I washed my brush in white spirit and wiped it on a paper towel. Later I noticed the towel was covered in flies that apparently suffered no harm. They stayed there for at least an hour. What kind of flies would be attracted to white spirit? I later found more flies drowned in a jar of white spirit some distance away. (Continued)
● The earlier reply to the question on the strange attraction of white spirit to the fruit fly Anomoia permunda linked their behaviour to the possibility that some substances in the white spirit were similar to those emitted by hawthorn fruit, which attract the flies to lay their eggs there. This reminded me of some work I was party to in South America a few years ago, on the control of the introduced exotic tephritid fruit fly Bactrocera carambolae (commonly known as the star fruit or carambola fruit fly). It showed how such apparently trivial observations can be turned into useful practical measures to control important pest species.
were made from small absorbent strips of board soaked in a mixture of methyl eugenol and the insecticide malathion. When they alighted on the baits, they were rapidly overcome by contact with the insecticide. No native species were affected, nor were the female carambola flies attracted to the baits, so the technique allowed very precisely targeted control of the invading species, and at an astonishingly low cost. This particular infestation – across Suriname, Guyana and French Guiana – occurred when the fly became capable of using local native fruit species to incubate its larval stage. Fortunately, the work we did ensured it was eliminated very quickly and prevented the spread of the fly across much of tropical South America. Doug Cross Lowick Bridge, Cumbria, UK
COOL COLOUR Why is frozen milk yellow?
The male of this species is attracted to traces of airborne methyl eugenol, a component of clove oil, which acts as a mating pheromone. In our tests, male flies were attracted to a ring of baits hung in trees around infested carambola fruit orchards. The baits
● The yellow colour of frozen milk comes from the vitamin riboflavin, which actually got its name from its colour – flavus is the Latin for yellow. Riboflavin is dissolved in the watery portion of milk, which is also filled with minute particles of protein and droplets of butterfat. In fresh milk, all the suspended particles and droplets scatter any light that strikes them evenly, so that the milk appears opaque and white – milky, in other words. However, as the milk freezes and most of its water crystallises into ice before other substances, the normally dilute riboflavin becomes
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.
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.
“Baits were soaked in methyl eugenol, which attracts star-fruit fruit flies, and insecticide”
concentrated in the remaining liquid water. This means these areas start to turn yellow and as the clear water-ice crystals form, we are able to see it. Harold McGee San Francisco, California, US Harold McGee is the author of On Food & Cooking: The science and lore of the kitchen (Fireside, 1997)
THIS WEEK’S QUESTIONS Readers have often contacted us to ask whether there is anything Jon Richfield – a prolific answerer of Last Word questions – does not know. Well, it seems there is – Ed Taste tribulation This is a question that my husband, Jon Richfield, cannot answer to my satisfaction. I find the taste of certain common spices quite horrible. The nasty flavour I get from all of them seems, to me, quite similar.
The spices that taste this way are aniseed, caraway, cumin, fennel and coriander. Tarragon, cardamom and capers also taste awful in the same way. I wonder if there is a food scientist who knows what they have in common, or what my aversion might be. I should add that I am not a fussy eater in general. Bess Richfield Somerset West, South Africa Fowl play This guineafowl feather (pictured below) embodies a challenge to embryologists. How does the bird grow pigmented cells in patterns of spots that must change as the feather grows in order to maintain the pattern? These patterns also overlie a separate and independent pattern contained throughout many feathers whose tissues cannot possibly react to the pigmentation in neighbouring feathers as they grow. So how is the overall pattern retained on the whole bird? Jon Richfield Somerset West, South Africa
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
● The earlier reply to the question on the strange attraction of white spirit to the fruit fly Anomoia permunda linked their behaviour to the possibility that some substances in the white spirit were similar to those emitted by hawthorn fruit, which attract the flies to lay their eggs there. This reminded me of some work I was party to in South America a few years ago, on the control of the introduced exotic tephritid fruit fly Bactrocera carambolae (commonly known as the star fruit or carambola fruit fly). It showed how such apparently trivial observations can be turned into useful practical measures to control important pest species.
were made from small absorbent strips of board soaked in a mixture of methyl eugenol and the insecticide malathion. When they alighted on the baits, they were rapidly overcome by contact with the insecticide. No native species were affected, nor were the female carambola flies attracted to the baits, so the technique allowed very precisely targeted control of the invading species, and at an astonishingly low cost. This particular infestation – across Suriname, Guyana and French Guiana – occurred when the fly became capable of using local native fruit species to incubate its larval stage. Fortunately, the work we did ensured it was eliminated very quickly and prevented the spread of the fly across much of tropical South America. Doug Cross Lowick Bridge, Cumbria, UK
COOL COLOUR Why is frozen milk yellow?
The male of this species is attracted to traces of airborne methyl eugenol, a component of clove oil, which acts as a mating pheromone. In our tests, male flies were attracted to a ring of baits hung in trees around infested carambola fruit orchards. The baits
● The yellow colour of frozen milk comes from the vitamin riboflavin, which actually got its name from its colour – flavus is the Latin for yellow. Riboflavin is dissolved in the watery portion of milk, which is also filled with minute particles of protein and droplets of butterfat. In fresh milk, all the suspended particles and droplets scatter any light that strikes them evenly, so that the milk appears opaque and white – milky, in other words. However, as the milk freezes and most of its water crystallises into ice before other substances, the normally dilute riboflavin becomes
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.
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.
“Baits were soaked in methyl eugenol, which attracts star-fruit fruit flies, and insecticide”
concentrated in the remaining liquid water. This means these areas start to turn yellow and as the clear water-ice crystals form, we are able to see it. Harold McGee San Francisco, California, US Harold McGee is the author of On Food & Cooking: The science and lore of the kitchen (Fireside, 1997)
THIS WEEK’S QUESTIONS Readers have often contacted us to ask whether there is anything Jon Richfield – a prolific answerer of Last Word questions – does not know. Well, it seems there is – Ed Taste tribulation This is a question that my husband, Jon Richfield, cannot answer to my satisfaction. I find the taste of certain common spices quite horrible. The nasty flavour I get from all of them seems, to me, quite similar.
The spices that taste this way are aniseed, caraway, cumin, fennel and coriander. Tarragon, cardamom and capers also taste awful in the same way. I wonder if there is a food scientist who knows what they have in common, or what my aversion might be. I should add that I am not a fussy eater in general. Bess Richfield Somerset West, South Africa Fowl play This guineafowl feather (pictured below) embodies a challenge to embryologists. How does the bird grow pigmented cells in patterns of spots that must change as the feather grows in order to maintain the pattern? These patterns also overlie a separate and independent pattern contained throughout many feathers whose tissues cannot possibly react to the pigmentation in neighbouring feathers as they grow. So how is the overall pattern retained on the whole bird? Jon Richfield Somerset West, South Africa
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