Why do mosquitoes whine and why do their bites sting? Both of these give warning of their presence, and neither do more than irritate any of their prey. One would have thought that natural selection would have removed or at least diminished both.
The whine of a mosquito, a female if it is about to attack you, is a simple product of its wingbeat, albeit at a higher frequency than the buzz of a bee. The male mosquitoes have plumed antennae, with which they detect the flying females — hence, no whine, no sex. The mosquitoes that pose the greatest threat to human existence, members of the genus Anopheles, are more lightly built than the so-called “nuisance mosquitoes”, mostly members of the genus Aedes or of the genus Culex. As a consequence they make much less of a whine and so do not disturb the sleeping prey (most Anopheles bite at night).
In a similar vein, my experience is that the “sting” of the bite is much greater in non-Anophelines. While some very large species, by mosquito standards, actually cause pain simply by penetrating the skin deeply enough to stimulate pain sensors, the irritation is mostly due to the adverse reaction to the injection of anti-coagulants and comes after the meal is over. The mosquito saliva may also contain anaesthetic components which ensure the prey does not realise it is being attacked.
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Dr Brian Taylor, Nottingham
It has been claimed that terrorists, or even lay people, could make an atomic weapon. Is it as easy as is sometimes claimed? Has it ever been done?
The basic physics and engineering of atom bombs have been known for decades. There are two types of weapon: the “gun” bomb and the implosion bomb. The gun bomb is simple to construct (South Africa produced some in the 1990s) but works only with highly enriched uranium (HEU) and not plutonium. HEU is produced only for military purposes and needs a large industrial facility. The implosion bomb works with either HEU or plutonium. However, making one requires a good deal of precision engineering — and exact knowledge of the ways the components interact.
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But in either case, the major problem is obtaining sufficient weapons-grade plutonium or uranium. That you cannot buy “off the shelf”, and plutonium produced in most commercial reactors is more difficult to use as it has more of the heavier isotopes of plutonium which are less suitable for military use.
Nicholas Hill, Farncombe, Surrey
Assuming access to the necessary implements and cooking facilities, how long could a person survive if trapped in a typical supermarket?
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The survival time would be far less than one would assume. The vital ingredient to survive is liquid. If our supermarket is anything to go by, the bulk of liquid in stock is alcoholic so the trapped person would die either of thirst or alcohol poisoning.
Dennis Ruddle, Cardiff