mountains

Rivers have been used as a source of water, for obtaining food, for transport, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste. Rivers have been used for navigation for thousands of years. The earliest evidence of navigation is found in the Indus Valley Civilization, which existed in northwestern Pakistan around 3300 BC.[13] Riverine navigation provides a cheap means of transport, and is still used extensively on most major rivers of the world like the Amazon, the Ganges, the Nile, the Mississippi, and the Indus. Since river boats are often not regulated, they contribute a large amount to global greenhouse gas emissions, and to local cancer due to inhaling of particulates emitted by the transports.[14][15] In some heavily forested regions such as Scandinavia and Canada, lumberjacks use the river to float felled trees downstream to lumber camps for further processing, saving much effort and cost by transporting the huge heavy logs by natural means. Rivers have been a source of food since pre-history.[16] They can provide a rich source of fish and other edible aquatic life, and are a major source of fresh water, which can be used for drinking and irrigation. It is therefore no surprise to find most of the major cities of the world situated on the banks of rivers. Rivers help to determine the urban form of cities and neighbourhoods and their corridors often present opportunities for urban renewal through the development of foreshoreways such as riverwalks. Rivers also provide an easy means of disposing of waste-water and, in much of the less developed world, other wastes.

rivers

Subsurface streams Most but not all rivers flow on the surface. Subterranean rivers flow underground in caves or caverns. Such rivers are frequently found in regions with limestone geologic formations. Subglacial streams are the braided rivers that flow at the beds of glaciers and ice sheets, permitting meltwater to be discharged at the front of the glacier. Because of the gradient in pressure due to the overlying weight of the glacier, such streams can even flow uphill. Permanence of flow An intermittent river (or ephemeral river) only flows occasionally and can be dry for several years at a time. These rivers are found in regions with limited or highly variable rainfall, or can occur because of geologic conditions such as having a highly permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter. Such rivers are typically fed from chalk aquifers which recharge from winter rainfall. In the UK these rivers are called Bournes and give their name to place such as Bournemouth and Eastbourne.

Rivers have been classified by many criteria including their topography, their biotic status, their relevance to white water rafting or canoeing activities.

rivers

A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. In 1757, the German hydrologist Albert Brahms empirically observed that the submerged weight of objects that may be carried away by a river is proportional to the sixth power of the river flow speed.[5] (This formulation is also sometimes called Airy's law.[6]) Thus, if the speed of flow were doubled, the flow would dislodge objects with 64 times as much submerged weight. In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks. In U-shaped glaciated valleys, the subsequent river valley can often easily be identified by the V-shaped channel that it has carved. In the middle reaches where the river may flow over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths, if conditions permit. Rivers whose mouths are in saline tidal waters may form estuaries. Throughout the course of the river, the total volume of water transported downstream will often be a combination of the free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain (called the hyporheic zone). For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow.

Topography

The water in a river is usually confined to a channel, made up of a stream bed between banks. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Flood plains may be very wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred especially in urban areas where the floodplain of a river channel can become greatly developed by housing and industry. The term upriver refers to the direction leading to the source of the river, which is against the direction of flow. Likewise, the term downriver describes the direction towards the mouth of the river, in which the current flows The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river. Extensive braided rivers are now found in only a few regions worldwide, such as the South Island of New Zealand. They also occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are also quite rare. They have multiple sinuous channels carrying large volumes of sediment.

Butterfly activities

Butterflies are complex creatures. Their day-to-day lives can be characterized by many activities. If you are observant you may see butterflies involved in many of the follow activities. To observe some activities, such as hybernation, may involve some detective work. To observe other activities such as basking, puddling, or migrating, you will need to be at the proper place at the proper time. Keep an activity log and see how many different butterflies you can spot involved in each activity. The information from the individual butterfly pages may give you some hints as to where (or on what plants) some of these activities are likely to occur.

The larval or caterpillar stage and the adult butterfly have very different food preferences, largely due to the differences in their mouth parts. Both types of foods must be available in order for the butterfly to complete its life cycle. Caterpillars are very particular about what they eat, which is why the female butterfly lays her eggs only on certain plants. She instinctively knows what plants will serve as suitable food for the hungry caterpillars that hatch from her eggs. Caterpillars don't move much and may spend their entire lives on the same plant or even the same leaf! Their primary goal is to eat as much as they can so that they become large enough to pupate. Caterpillars have chewing mouth parts, called mandibles, which enable them to eat leaves and other plant parts. Some caterpillars are considered pests because of the damage they do to crops. Caterpillars do not need to drink additional water because they get all they need from the plants they eat.

Butterfly life cycle

Both butterflies and moths belong to the same insect group called Lepidoptera. In general, butterflies differ from moths in the following ways: (1) Butterflies usually have clubbed antennae but moths have fuzzy or feathery antennae. (2) Butterflies normally are active during the daytime while most moths are active at night. (3) When a butterfly rests, it will do so with its wings held upright over its body. Moths, on the other hand, rest with their wings spread out flat. Butterflies will, however, bask with their wings out-stretched. (4) Butterflies are generally more brightly colored than moths, however, this is not always the case. There are some very colorful moths. A life cycle is made up of the stages that a living organism goes through during its lifetime from beginning to end. A butterfly undergoes a process called complete metamorphosis during its life cycle. This means that the butterfly changes completely from its early larval stage, when it is a caterpillar, until the final stage, when it becomes a beautiful and graceful adult butterfly. The butterfly life cycle has four stages: egg, larva, pupa, and adult.

butterfly

Butterfly

mp to: navigation, search For other uses, see Butterfly (disambiguation)

mp to: navigation, search For other uses, see Butterfly (disambiguation). Page semi-protected Butterflies Temporal range: Eocene-Recent, 45–0 Ma PreЄ Є O S D C P T J K Pg N Charaxes brutus natalensis in Dar es Salaam, Tanzania Scientific classification Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Lepidoptera (unranked): Rhopalocera Subgroups Superfamily Hedyloidea: Hedylidae Superfamily Hesperioidea: Hesperiidae Superfamily Papilionoidea: Papilionidae Pieridae Nymphalidae Lycaenidae Riodinidae A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. Butterflies comprise the true butterflies (superfamily Papilionoidea), the skippers (superfamily Hesperioidea) and the moth-butterflies (superfamily Hedyloidea). All the many other families within the Lepidoptera are referred to as moths. The earliest known butterfly fossils date to the mid Eocene epoch, between 40–50 million years ago.[1]

Butterflies exhibit polymorphism, mimicry and aposematism. Some, like the Monarch, will migrate over long distances. Some butterflies have evolved symbiotic and parasitic relationships with social insects such as ants. Some species are pests because in their larval stages they can damage domestic crops or trees; however, some species are agents of pollination of some plants, and caterpillars of a few butterflies (e.g., Harvesters) eat harmful insects. Culturally, butterflies are a popular motif in the visual and literary arts.

Eggs

Butterfly eggs are protected by a hard-ridged outer layer of shell, called the chorion. This is lined with a thin coating of wax which prevents the egg from drying out before the larva has had time to fully develop. Each egg contains a number of tiny funnel-shaped openings at one end, called micropyles; the purpose of these holes is to allow sperm to enter and fertilize the egg. Butterfly and moth eggs vary greatly in size between species, but they are all either spherical or ovate.

Butterfly eggs are fixed to a leaf with a special glue which hardens rapidly. As it hardens it contracts, deforming the shape of the egg. This glue is easily seen surrounding the base of every egg forming a meniscus. The nature of the glue is unknown and is a suitable subject for research. The same glue is produced by a pupa to secure the setae of the cremaster. This glue is so hard that the silk pad, to which the setae are glued, cannot be separated. Eggs are almost invariably laid on plants. Each species of butterfly has its own hostplant range and while some species of butterfly are restricted to just one species of plant, others use a range of plant species, often including members of a common family. The egg stage lasts a few weeks in most butterflies but eggs laid close to winter, especially in temperate regions, go through a diapause (resting) stage, and the hatching may take place only in spring. Other butterflies may lay their eggs in the spring and have them hatch in the summer. These butterflies are usually northern species, such as the Mourning Cloak (Camberwell Beauty) and the Large and Small Tortoiseshell butterflies.[citation needed]

Mimicry

Batesian and Mullerian mimicry in butterflies is common. Batesian mimics imitate other species to enjoy the protection of an attribute they do not share, aposematism in this case. The Common Mormon of India has female morphs which imitate the unpalatable red-bodied swallowtails, the Common Rose and the Crimson Rose. Mullerian mimicry occurs when aposematic species evolve to resemble each other, presumably to reduce predator sampling rates, the Heliconius butterflies from the Americas beiHabitsng a good example. Wing markings called eyespots are present in some species; these may have an automimicry role for some species. In others, the function may be intraspecies communication, such as mate attraction. In several cases, however, the function of butterfly eyespots is not clear, and may be an evolutionary anomaly related to the relative elasticity of the genes that encode the spots.

Habits

Butterflies feed primarily on nectar from flowers. Some also derive nourishment from pollen,[22] tree sap, rotting fruit, dung, decaying flesh, and dissolved minerals in wet sand or dirt. Butterflies are important as pollinators for some species of plants although in general they do not carry as much pollen load as bees. They are however capable of moving pollen over greater distances.[23] Flower constancy has been observed for at least one species of butterfly.

Many species of butterfly maintain territories and actively chase other species or individuals that may stray into them. Some species will bask or perch on chosen perches. The flight styles of butterfliMigrationes are often characteristic and some species have courtship flight displays. Basking is an activity which is more common in the cooler hours of the morning. Many species will orient themselves to gather heat from the sun. Some species have evolved dark wingbases to help in gathering more heat and this is especially evident in alpine forms.

Migration

Many butterflies migrate over long distances. Particularly famous migrations are those of the Monarch butterfly from Mexico to northern USA and southern Canada, a distance of about 4000 to 4800 km (2500–3000 miles). Other well known migratory species include the Painted Lady and several of the Danaine butterflies. Spectacular and large scale migrations associated with the Monsoons are seen in peninsular India.[35] Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes.[36][37] Butterflies have been shown to navigate using time compensated sun compasses. They can see polarized light and therefore orient even in cloudy conditions. The polarized light in the region close to the ultraviolet spectrum is suggested to be particularly important.[38] It is suggested that most migratory butterflies are those that belong to semi-arid areas where breeding seasons are short.[39] The life-histories of their..

es. Many butterflies migrate over long distances. Particularly famous migrations are those of the Monarch butterfly from Mexico to northern USA and southern Canada, a distance of about 4000 to 4800 km (2500–3000 miles). Other well known migratory species include the Painted Lady and several of the Danaine butterflies. Spectacular and large scale migrations associated with the Monsoons are seen in peninsular India.^[35] Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes.
Butterflies have been shown to navigate using time compensated sun compasses. They can see polarized light and therefore orient even in cloudy conditions. The polarized light in the region close to the ultraviolet spectrum is suggested to be particularly important.
It is suggested that most migratory butterflies are those that belong to semi-arid ar Butterflies have been shown to navigate using time compensated sun compasses. They can see polarized light and therefore orient even in cloudy conditions. The polarized light in the region close to the ultraviolet spectrum is suggested to be particularly important.
eas where breeding seasons are short. The life-histories of their host plants also influence the strategies of

It is suggested that most migratory butterflies are those that belong to semi-arid areas where breeding seasons are short.[39] The life-histories of their host plants also influence the strategies of the butterflies.[40]

It is suggested that most migratory butterflies are those that belong to semi-arid areas where breeding seasons are shot...

Defense

Butterflies are threatened in their early stages by parasitoids and in all stages by predators, diseases and

environmental factors. They protect themselves by a variety of means. Chemical defenses are widespread and are mostly based on chemicals of plant origin. In many cases the plants themselves evolved these toxic substances as protection against herbivores. Butterflies have evolved mechanisms to sequester these plant toxins and use them instead in their own defense.[41] These defense mechanisms are effective only if they are also well advertised and this has led to the evolution of bright colours in unpalatable butterflies. This signal may be mimicked by other butterflies. These mimetic forms are usually restricted to the females.

Life cycle and foodplants

The eggs are laid singularly on a wide range of foodplants including Hedge mustard Sisybrium officinale Garlic Mustard Alliaria petiolata, Cuckooflower Cardamine pratense, Water-cress Rorippa nastutium-aquaticum, Charlock Sinapis arvensis, Large bitter-cress Cardamine amara, wild cabbage Brassica oleracea and wild Radish Raphanus raphanistrum and so it is rarely a pest in gardens. The caterpillar is green and well camouflaged. It is often found feeding on the same plant as the Orange Tip but never competes for food because it only feeds on the leaves whereas the Orange Tip caterpillar feeds on the flowers and developing seed pods. Like other Pieris spp. it overwinters as a pupa. Habitat

Habitat

Pieris napi is found in damp, grassy places with some shade, forest edges, hedgerows, meadows and wooded river valleys. The later generations, widen their catchment areas in the search for alternative forage crops in drier, but flowery places . In the Mediterranean the insect is also found in scrub around mountain streams or springs and on floodplains with Nasturtium officinale. It is found from sea level to high altitude (2500m. in Central Europe centrale, 2600 m in Italy).