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The mosquito (Culex pipiens) lays its eggs in stagnant water. The eggs stick together in a ‘raft’ and are buoyed up by the air trapped between them. The eggs hatch into larvae which escape into the water from the bottom of the egg cases. The larvae hang from the surface film of the water by means of a breathing tube, through which they take in air. If disturbed, they swim by flicking movements to the bottom, and then return to the surface. They feed on microscopic plants which they collect by whisking movements of their mouthparts which carry a dense fringe of bristles. They shed their ‘skins’ at intervals as they grow.

By the time the last larval ‘skin’ is shed, the larva has turned into a pupa, quite different in appearance from the larva. The pupa does not feed but continues to breath air through two breathing tubes while hanging from the surface film of the water.

By this time, the pupa has developed all the features of the adult: wings, legs, compound eyes etc. but these are all crammed into the pupal skin, giving it a somewhat grotesque comma shape.

The pupal case eventually breaks open at the top and the adult mosquito works its way out and supports itself on the floating pupal case and the surface film while its wings expand and harden before it flies away.

The adult mosquito has 3 pairs of legs and one pair of wings on its thorax. Its head bears a set of mouthparts which are adapted to piercing and sucking. The female mosquito often feeds on blood before she lays her eggs. She lands on a suitable animal and pushes her sharp piercing mouthparts through the skin until they reach a capillary blood vessel. She injects saliva which contains a substance that prevents the blood from clotting, and then sucks up a meal of blood which is digested in her gut. The mouthparts of male mosquitoes cannot penetrate the skin, and males feed on plant juices such as nectar.

When humans are ‘bitten’ by a mosquito, the salivary secretions often lead to an inflamed itchy swelling. In the tropics, however, the bite of a mosquito can transmit the disease malaria.

More information, and illustrations to accompany this article, can be found on biology-resources.com

Astronomy and Cosmology

Cosmology is the name given to a range of natural sciences, including both physics and astronomy that intends to provide an explanation for how the universe works as an integrated entity. Over the centuries, since the Pythagoreans in Greece during the 6th century BC considered the possibility that Earth was spherical, cosmology has come a long way and has integrated a variety of different fields of science.

Cosmology evolved from the observation of these Greeks who interpreted the natural laws of the heavenly bodies from which, eventually, the Ptolemaic model developed during the second century AD. Centuries later, during the 16th century, the Copernican system further developed the theories surrounding astronomy and cosmology – followed, in the 20th century, by the theories of special relativity and Albert Einstein’s Theory of General Relativity. Overall, however, the case for cosmology states that the laws of physics work the same everywhere and that there is homogeneity throughout the universe.

‘The Holographic Universe’, written by Michael Talbot, tells its story in two parts: the first part devotes 55 pages to discussing David Bohm’s holographic model of the universe – simplified into everyday language by Talbot. The second part of the book delves into events of the paranormal while, at the same time, attempting to rationalise the holographic model. Talbot introduces the reader to Karl Pribram as well as the philosophies of David Bohm.

Chemistry

Chemistry and biochemistry often go hand-in-hand, existing in parallel with other scientific disciplines such as dietetics [the science of food]. McCance and Widdowson, who produce ‘The Composition of Foods’ summarises food composition tables and updates much in the way of nutrition as a science. The foreword to the 6th edition has been written by Sir John Krebs while the actual volume itself provides an invaluable source of reference to dieticians and nutritionists the world over.

Meanwhile,’Principles of Biochemistry’ by Nelson D has been described as a ‘modern approach to biochemistry’. Personally, one of the best biochemistry books I have ever encountered was that written by Patterson – now, sadly, long since out of print. I attribute my successful pass in the biochemistry exams to the presence of Patterson which, by the time I had finished with it, was particularly dog-eared! Nelson D’s ‘Principles of Biochemistry’ really is the next best thing to Patterson and a worthy successor.

Earth Sciences and Geography

Earth sciences are a catch-all term covering a different range of natural sciences from those mentioned above. These relate to the study of the earth and how different parts of it are interlinked to produce that homogenous whole that is the classic feature of the scientific world. If you are interested in the world around you then you may be interested in a lovely book by Gavin Pretor-Pinney. This book ‘The Cloud Collector’s Handbook’ is full of charming pictures, below which you will find a short description of each cloud and space for you to record your own sightings. It certainly gives a new connotation to having your head in the clouds!

Education

If you think about it, there is all the difference in the world between someone who loves school and somebody who loves to learn: it doesn’t necessarily follow that, if you love to learn, then you must enjoy school. Education, however, is all about learning for the sheer pleasure of gaining new information. This learning may or may not be associated with school: it can even cover any subject. Evidence of this can be seen in Richard Dawkins’ book ‘The Greatest Show on Earth: The Evidence for Evolution’.

Dawkins goes about educating his readers, explaining to them how fossils can be dated accurately, all about plate tectonics etc, before going into the details of how these may be linked with the global distribution of plants and animals and the effects changes in these physical elements can have on them. Dawkins, whilst making it clear that he is aware [and who could not be?] of the great debate on creation v evolution, doesn’t get drawn into the minutiae surrounding this eternal dispute.

Engineering and Technology

One book that I simply have to recommend is a fantastic book written by Jo Marchant. You will find it in our Science and Nature section under the heading of Engineering and Technology. The first thing to say is that this is not some dry and boring technical tome. This book relates the story behind a particularly ancient Greek artefact and what it took to decode its hidden mysteries. The book is called ‘Decoding the Heavens: Solving the Mystery of the World’s First Computer’. I wish Jo Marchant had found a more intriguing title for her book because this title really doesn’t do this book justice.

The book relates the story of the Antikythera Mechanism which has been shown to have amazing capabilities as an astronomical calculator: scientists believe its complexity was at least 1500 years before its time. The Antikythera Mechanism artifact is a good 2,000 years old and was found during a dive in 1901. Scientists have been attempting to unravel its secrets ever since. So, if it’s a true-life mystery you are interested, or a book that’s a bit different I would strongly recommend this well-written and interesting book of Jo Marchant’s.

There are innumerable other sub-genres to be found within our Science and Nature section, covering quite an array of subjects. If you are a fan of the border collie, Barbara Sykes writes a delightful treatise on ‘Understanding Border Collies’. This is an excellent book written by somebody who really does understand the intricacies that go to make up this breed of dog and is an absolute ‘must have’ for all the lovers of border collies out there. Changing from dogs to elephants, I would certainly recommend ‘The Elephant Whisperer: Learning about Life, Loyalty and Freedom from a Remarkable Herd of Elephants’ – it will really pull on your heartstrings then have you howling with laughter! Check out all the other options within this section – you will probably amaze yourself at the treasure trove of titles hidden within our web pages!

Aphids are representative of a group of insects which obtain their food by piercing plant or animal tissues with sharp mouthparts and sucking up the body fluids. To gardeners and farmers, aphids can be serious pests. The gardener will be familiar with ‘greenfly’ on roses and ‘blackfly’ on broad bean plants.

Life cycle. In the summer months, all the aphids seen will be females and most of those on plants will be wingless. They reproduce at this time by a process called ‘parthenogenesis’ in which no sexual process occurs. The females do not lay eggs but deliver their young, called nymphs, alive.

The nymphs are like miniature adults and soon reach full size after a series of ‘moults’. From time to time, some of these nymphs develop wings and fly off to infest new plants.

In Autumn, some of the winged forms are males which fly off to a nearby tree or shrub. They are joined by winged females which produce wingless daughters. These daughters then mate with the males and lay eggs on the branches of the tree. The eggs have thick shells and can withstand low temperatures throughout the winter. In Spring, the eggs hatch to wingless females which feed on the young tree leaves, producing daughters parthenogenetically. Some of these daughters will be winged and fly away to reach the plants on which they feed during the Summer.

Feeding. Aphids have elongated mouth parts which fit together to form a piercing and sucking tube, a proboscis. On a leaf, they insert this proboscis through the leaf tissue until it reaches the food-conducting cells (phloem cells). They inject a little saliva which starts to digest the cell contents and then suck up the fluid into their gut.

The plant sap contains more sugars than amino acids (protein precursors) and the aphids excrete a solution of the excess sugar through their anus. This liquid is popularly called ‘honey dew’ and when it falls on the leaf, it encourages the growth of mould. However, ants have a great liking for this ‘honey dew’ and clamber over the feeding aphids to collect it.

The feeding habits of aphids damage the leaves, making them curl up, dry out and fall off. This effect coupled with the fact that the plant is deprived of some of its nutrients can cause a loss in yield from crop plants and vegetables. Aphids also spread plant viruses by their feeding habits.

Control The aphids are preyed upon by ladybirds and their larvae and the larvae of lacewings. These predators control the aphid population to some extent but gardeners and farmers often have to resort to pesticides. Some of these simply kill the aphids on contact and may be as innocuous as soap solution. Since the aphid penetrates the plant leaf in order to feed, spreading insecticide on the leaf surface is ineffective and recourse is made to systemic insecticides. The plant absorbs these insecticides into its tissues so that the aphid is poisoned when it takes up the cellular fluids. The insecticides break down after a short time so they are not present in the harvested crop.