A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera. Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, an elongated body. Dragonflies can be mistaken for the related group, which are similar in structure, though lighter in build. Dragonflies are agile fliers. Many dragonflies have brilliant iridescent or metallic colours produced by structural coloration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each. Fossils of large dragonfly ancestors in the Protodonata are found from 325 million years ago in Upper Carboniferous rocks. There are about 3,000 extant species. Most are tropical, with fewer species in temperate regions. Dragonflies are predators, both in their aquatic larval stage, they are known as nymphs or naiads, as adults. Several years of their lives are spent as nymphs living in fresh water, they are fast, agile fliers, sometimes migrating across oceans, live near water.
They have a uniquely complex mode of reproduction involving indirect insemination, delayed fertilization, sperm competition. During mating, the male grasps the female at the back of the head, the female curls her abdomen under her body to pick up sperm from the male's secondary genitalia at the front of his abdomen, forming the "heart" or "wheel" posture. Loss of wetland habitat threatens dragonfly populations around the world. Dragonflies are represented in human culture on artifacts such as pottery, rock paintings, Art Nouveau jewellery, they are used in traditional medicine in Japan and China, caught for food in Indonesia. They are symbols of courage and happiness in Japan, but seen as sinister in European folklore, their bright colours and agile flight are admired in the poetry of Lord Tennyson and the prose of H. E. Bates. Dragonflies and their relatives are an ancient group; the oldest fossils are of the Protodonata from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that lived, Meganeuropsis permiana from the early Permian, with a wingspan around 750 mm.
The Protanisoptera, another ancestral group which lacks certain wing vein characters found in modern Odonata, lived from the Early to Late Permian age until the end Permian event, are known from fossil wings from current day United States and Australia, suggesting they might have been cosmopolitan in distribution. The forerunners of modern Odonata are included in a clade called the Panodonata, which include the basal Zygoptera and the Anisoptera. Today there are some 3000 species extant around the world; the relationships of anisopteran families are not resolved as of 2013, but all the families are monophyletic except the Corduliidae. On the cladogram, dashed lines indicate unresolved relationships; the distribution of diversity within the biogeographical regions are summarised below. Dragonflies live on every continent except Antarctica. In contrast to the damselflies, which tend to have restricted distributions, some genera and species are spread across continents. For example, the blue-eyed darner Rhionaeschna multicolor lives all across North America, in Central America.
The globe skimmer Pantala flavescens is the most widespread dragonfly species in the world. Most Anisoptera species are tropical, with far fewer species in temperate regions; some dragonflies, including libellulids and aeshnids, live in desert pools, for example in the Mojave Desert, where they are active in shade temperatures between 18 and 45 °C. Dragonflies live from sea level up to the mountains, their altitudinal limit is about 3700 m, represented by a species of Aeshna in the Pamirs. Dragonflies become scarce at higher latitudes, they are not native to Iceland, but individuals are swept in by strong winds, including a Hemianax ephippiger native to North Africa, an unidentified darter species. In Kamchatka, only a few species of dragonfly including the treeline emerald Somatochlora arctica and some aeshnids such as Aeshna subarctica are found because of the low temperature of the lakes there; the treeline emerald lives in northern Alaska, within the Arctic Circle, making it the most northerly of all dragonflies.
Dragonflies are heavy-bodied, strong-flying insects that hold their win
A primordium in embryology, is an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells. A primordium is the simplest set of cells capable of triggering growth of the would-be organ and the initial foundation from which an organ is able to grow. In flowering plants, a floral primordium gives rise to a flower. Although it is a used term in plant biology, the word is used in describing the biology of all multicellular organisms Plants produce both leaf and flower primordia cells at the shoot apical meristem. Primordium development in plants is critical to the proper positioning and development of plant organs and cells; the process of primordium development is intricately regulated by a set of genes that affect the positioning and differentiation of the primordium. Genes including STM and CUC are involved in defining the borders of the newly formed primordium; the plant hormone auxin has been implicated in this process, with the new primordium being initiated at the placenta, where the auxin concentration is highest.
There is still much to understand about the genes involved in primordium development. Leaf primordia are groups of cells; these new leaves resemble knobby outgrowths or inverted cones. Flower primordia are the little buds. Flower primordia start off as a crease or indentation and form into a bulge; this bulging is caused by less anisotropic, or directionally dependent, growth. Anlage Morphogenesis Primordial phallus List of biological development disorders
Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insects from other arthropods: they have a body divided into three regions, have three pairs of legs, mouthparts located outside of the head capsule, it is this position of the mouthparts which divides them from their closest relatives, the non-insect hexapods, which includes Protura and Collembola. There is enormous variation in body structure amongst insect species. Individuals can range from 0.3 mm to 30 cm across. These modifications allow insects to occupy every ecological niche on the planet, except the deep ocean and the Antarctic; this article describes the basic insect body and some of the major variations of the different body parts. Insects, like all arthropods, have no interior skeleton; the insect body is divided into three parts: the head and abdomen.
The head is specialized for sensory food intake. Although the general function of the three body regions is the same across all insect species, there are major differences in basic structure, with wings, legs and mouthparts being variable from group to group; the insect outer skeleton, the cuticle, is made up of two layers. This is chitinous and much thicker than the epicuticle and has two layers, the outer is the exocuticle while the inner is the endocuticle; the tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each other in a sandwich pattern, while the exocuticle is rigid and sclerotized. The exocuticle is reduced in many soft-bodied insects the larval stages. Chemically, chitin is a long-chain polymer of a derivative of glucose. In its unmodified form, chitin is translucent, pliable and quite tough. In arthropods, however, it is modified, becoming embedded in a hardened proteinaceous matrix, which forms much of the exoskeleton. In its pure form, it is leathery.
The difference between the unmodified and modified forms can be seen by comparing the body wall of a caterpillar to a beetle. From the embryonic stages itself, a layer of columnar or cuboidal epithelial cells gives rise to the external cuticle and an internal basement membrane; the majority of insect material is held in the endocuticle. The cuticle acts as a protective shield as the insect develops. However, since it cannot grow, the external sclerotised part of the cuticle is periodically shed in a process called "moulting"; as the time for moulting approaches, most of the exocuticle material is reabsorbed. In moulting, first the old cuticle separates from the epidermis. Enzymatic moulting fluid is released between the old cuticle and epidermis, which separates the exocuticle by digesting the endocuticle and sequestering its material for the new cuticle; when the new cuticle has formed sufficiently, the epicuticle and reduced exocuticle are shed in ecdysis. The four principal regions of an insect body segment are: tergum or dorsal, sternum or ventral and the two pleura or laterals.
Hardened plates in the exoskeleton are called sclerites, which are subdivisions of the major regions - tergites and pleurites, for the respective regions tergum and pleuron. The head in most insects is enclosed in a hard sclerotized, exoskeletal head capsule'; the main exception is in those species whose larvae are not sclerotised some holometabola. The larvae of Cyclorrhapha however, tend to have hardly any head capsule at all; the head capsule bears most of the main sensory organs, including the antennae and the compound eyes. It bears the mouthparts. In the adult insect the head capsule is unsegmented, though embryological studies show it to consist of six segments that bear the paired head appendages, including the mouthparts, each pair on a specific segment; each such pair occupies one segment, though not all segments in modern insects bear any visible appendages. Of all the insect orders, Orthoptera most conveniently display the greatest variety of features found in the heads of insects, including the sutures and sclerites.
Here, the vertex, or the apex, is situated between the compound eyes for insects with hypognathous and opisthognathous heads. In prognathous insects, the vertex is not found between the compound eyes, but rather, where the ocelli are found; this is because the primary axis of the head is rotated 90° to become parallel to the primary axis of the body. In some species, this region assumes a different name; the ecdysial suture is made of the coronal and epicranial sutures plus the ecdysial and cleavage lines, which vary among different species of insects. T
Damselflies are insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies, which constitute the other odonatan suborder, but are smaller, have slimmer bodies, most species fold the wings along the body when at rest. An ancient group, damselflies have existed since at least the Lower Permian, are found on every continent except Antarctica. All damselflies are predatory; the nymphs are aquatic, with different species living in a variety of freshwater habitats including acid bogs, ponds and rivers. The nymphs moult at the last moult climbing out of the water to undergo metamorphosis; the skin splits down the back, they emerge and inflate their wings and abdomen to gain their adult form. Their presence on a body of water indicates that it is unpolluted, but their dependence on freshwater makes them vulnerable to damage to their wetland habitats; some species of damselfly have elaborate courtship behaviours. Many species are sexually dimorphic, the males being more brightly coloured than the females.
Like dragonflies, they reproduce using delayed fertilisation. A mating pair form a shape known as a "heart" or "wheel", the male clasping the female at the back of the head, the female curling her abdomen down to pick up sperm from secondary genitalia at the base of the male's abdomen; the pair remain together with the male still clasping the female while she lays eggs within the tissue of plants in or near water using a robust ovipositor. Fishing flies. Damselflies sometimes provide the subject for personal jewellery such as brooches; the Zygoptera are an ancient group, with fossils known from the lower Permian, at least 250 million years ago. All the fossils of that age are of adults, similar in structure to modern damselflies, so it is not known whether their larvae were aquatic at that time; the earliest larval odonate. Fossils of damselfly-like Protozygoptera date back further to 311–30 Mya. Well-preserved Eocene damselfly larvae and exuviae are known from fossils preserved in amber in the Baltic region.
Molecular analysis in 2013 confirms that most of the traditional families are monophyletic, but shows that the Amphipterygidae, Megapodagrionidae and Protoneuridae are paraphyletic and will need to be reorganised. The Protoneuridae in particular is shown to be composed of six clades from five families; the result so far is 27 damselfly families, with 7 more to be created. The discovered clades did not agree well with traditional characteristics used to classify living and fossil Zygoptera such as wing venation, so fossil taxa will need to be revisited; the 18 extant traditional families are provisionally rearranged as follows: Dashed lines indicate unresolved relationships. The general body plan of a damselfly is similar to that of a dragonfly; the compound eyes are large but are more separated and smaller than those of a dragonfly. Above the eyes is the frons or forehead, below this the clypeus, on the upper lip the labrum, an extensible organ used in the capture of prey; the top of the head bears three simple eyes, which may measure light intensity, a tiny pair of antennae that serve no olfactory function but may measure air speed.
Many species are sexually dimorphic. For example, in Coenagrion, the Eurasian bluets, the males are bright blue with black markings, while the females are predominantly green or brown with black. A few dimorphic species show female-limited polymorphism, the females being in two forms, one form distinct and the other with the patterning as in males; the ones that look like males, are under a third of the female population but the proportion can rise and a theory that explains this response suggests that it helps overcome harassment by males. Some Coenagrionid damselflies show male-limited polymorphism, an less understood phenomenon. In general, damselflies are smaller than dragonflies, the smallest being members of the genus Agriocnemis. However, members of the Pseudostigmatidae are exceptionally large for the group, with wingspans as much as 19 cm in Megaloprepus and body length up to 13 cm in Pseudostigma aberrans; the first thoracic segment is the prothorax. The joint between head and prothorax is slender and flexible, which enables the damselfly to swivel its head and to manoeuvre more when flying.
The remaining thoracic segments are the fused mesothorax and metathorax, each with a pair of wings and a pair of legs. A dark stripe known as the humeral stripe runs from the base of the front wings to the second pair of legs, just in front of this is the pale-coloured, antehumeral stripe; the forewings and hindwings are similar in appearance and are membranous, being strengthened and supported by longitudinal veins that are linked by many cross-veins and that are filled with haemolymph. Species markers include quadrangular markings on the wings known as the pterostigma or stigma, in all species, there is a nodus near the leading edge; the thorax houses the flight muscles. Many damselflies have clear wings, but some have coloured wings, whether uniformly suffused with colour or boldly marked with a coloured patch. In species such as the banded demoiselle, Calopteryx splendens the males have both a d
Bombyx mandarina, the wild silkmoth, is an insect from the moth family Bombycidae. It is the closest relative of Bombyx mori the domesticated silkmoth or "silkworm". Unlike the domesticated relative, unable to fly or indeed persist outside human care, the wild silkmoth is a ordinary lepidopteran, its main difference from the domesticated taxon is the more slender body with well-developed wings in males, the dull greyish-brown colour. Bombyx mandarina and the domesticated Bombyx mori constitute two of the identified eight species of the genus Bombyx, the true or mulberry silkmoths; the origin of the domesticated silkmoth is enigmatic. It has been suggested that it is the survivor of an extinct species which diverged from the ancestors of Bombyx mandarina millions of years ago. However, this is based on an untenable molecular clock hypothesis that assumes that wild and domestic silkmoths evolved fast after their lineages diverged. Rather, the effects of artificial selection have accelerated evolution in the domestic form to a point where it is hard to trace the origin of the numerous breeds of domestic silkworms with the most modern molecular phylogeny methods.
Conceivably, today's domesticated silkworms are all descended from an initial stock of B. mandarina collected as late as 5000 years ago. While wild silk could have been collected and used as threads, etc. since much earlier, the technology to breed and use silkworms from a domesticated stock did not exist before the late Neolithic. However, it has been possible to trace the geographical origin of the domestic silkmoth; the wild species occurs over a considerable range from inland China to Korea and Japan, shows much variation. The populations from the northeastern end of the range, for example, differ in karyotype from those of inland China. Domestic silkmoths are closer to the latter regarding mtDNA sequence data, lack some genetic apomorphies of the northeastern B. mandarina. Thus, the initial domestic stock came from inland China. B. Mandarina is able to hybridize with B. mori. Both in the wild and in a domesticated environment, females release pheromones and wait for males to be attracted and fly to them.
However, B. mori males cannot fly. Hybridisation in the wild, therefore means breeding between domestic females and wild males. Hybridization is possible in both directions in a domesticated environment; the two silkmoths have been united as subspecies of a single species. However, today it is recognized that the domesticated silkmoth is dependent on human care for its survival and thus has a level of reproductive isolation from its wild relatives. Japanese Moths: Bombyx mandarina. Contains many photos. Retrieved 18 July 2007. Copulation between female B. mandarina and male B. mori in captivity. Note stunted wings of male. Retrieved 18 July 2007
Anatomical terms of location
Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans. All vertebrates have the same basic body plan – they are bilaterally symmetrical in early embryonic stages and bilaterally symmetrical in adulthood; that is, they have mirror-image left and right halves if divided down the middle. For these reasons, the basic directional terms can be considered to be those used in vertebrates. By extension, the same terms are used for many other organisms as well. While these terms are standardized within specific fields of biology, there are unavoidable, sometimes dramatic, differences between some disciplines. For example, differences in terminology remain a problem that, to some extent, still separates the terminology of human anatomy from that used in the study of various other zoological categories. Standardized anatomical and zoological terms of location have been developed based on Latin and Greek words, to enable all biological and medical scientists to delineate and communicate information about animal bodies and their component organs though the meaning of some of the terms is context-sensitive.
The vertebrates and Craniata share a substantial heritage and common structure, so many of the same terms are used for location. To avoid ambiguities this terminology is based on the anatomy of each animal in a standard way. For humans, one type of vertebrate, anatomical terms may differ from other forms of vertebrates. For one reason, this is because humans have a different neuraxis and, unlike animals that rest on four limbs, humans are considered when describing anatomy as being in the standard anatomical position, thus what is on "top" of a human is the head, whereas the "top" of a dog may be its back, the "top" of a flounder could refer to either its left or its right side. For invertebrates, standard application of locational terminology becomes difficult or debatable at best when the differences in morphology are so radical that common concepts are not homologous and do not refer to common concepts. For example, many species are not bilaterally symmetrical. In these species, terminology depends on their type of symmetry.
Because animals can change orientation with respect to their environment, because appendages like limbs and tentacles can change position with respect to the main body, positional descriptive terms need to refer to the animal as in its standard anatomical position. All descriptions are with respect to the organism in its standard anatomical position when the organism in question has appendages in another position; this helps avoid confusion in terminology. In humans, this refers to the body in a standing position with arms at the side and palms facing forward. While the universal vertebrate terminology used in veterinary medicine would work in human medicine, the human terms are thought to be too well established to be worth changing. Many anatomical terms can be combined, either to indicate a position in two axes or to indicate the direction of a movement relative to the body. For example, "anterolateral" indicates a position, both anterior and lateral to the body axis. In radiology, an X-ray image may be said to be "anteroposterior", indicating that the beam of X-rays pass from their source to patient's anterior body wall through the body to exit through posterior body wall.
There is no definite limit to the contexts in which terms may be modified to qualify each other in such combinations. The modifier term is truncated and an "o" or an "i" is added in prefixing it to the qualified term. For example, a view of an animal from an aspect at once dorsal and lateral might be called a "dorsolateral" view. Again, in describing the morphology of an organ or habitus of an animal such as many of the Platyhelminthes, one might speak of it as "dorsiventrally" flattened as opposed to bilaterally flattened animals such as ocean sunfish. Where desirable three or more terms may be agglutinated or concatenated, as in "anteriodorsolateral"; such terms sometimes used to be hyphenated. There is however little basis for any strict rule to interfere with choice of convenience in such usage. Three basic reference planes are used to describe location; the sagittal plane is a plane parallel to the sagittal suture. All other sagittal planes are parallel to it, it is known as a "longitudinal plane".
The plane is perpendicular to the ground. The median plane or midsagittal plane is in the midline of the body, divides the body into left and right portions; this passes through the head, spinal cord, and, in many animals, the tail. The term "median plane" can refer to the midsagittal plane of other structures, such as a digit; the frontal plane or coronal plane divides the body into ventral portions. For post-embryonic humans a coronal plane is vertical and a transverse plane is horizontal, but for embryos and quadrupeds a coronal plane is horizontal and a transverse plane is vertical. A longitudinal plane is any plane perpendicular to the transverse plane; the coronal plane and the sagittal plane are examples of longitudinal planes. A transverse plane known as a cross-section, divides the body into cranial and caudal portions. In human anatomy: A transverse plane is an X-Z plane, parallel to the ground, which s
Lepidoptera is an order of insects that includes butterflies and moths. About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 per cent of the total described species of living organisms, it is one of the most widespread and recognizable insect orders in the world. The Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest the order may have more species than earlier thought, is among the four most speciose orders, along with the Hymenoptera and Coleoptera. Lepidopteran species are characterized by more than three derived features; the most apparent is the presence of scales that cover the bodies, a proboscis. The scales are modified, flattened "hairs", give butterflies and moths their wide variety of colors and patterns. All species have some form of membranous wings, except for a few that have reduced wings or are wingless. Mating and the laying of eggs are carried out by adults near or on host plants for the larvae.
Like most other insects and moths are holometabolous, meaning they undergo complete metamorphosis. The larvae are called caterpillars, are different from their adult moth or butterfly forms, having a cylindrical body with a well-developed head, mandible mouth parts, three pairs of thoracic legs and from none up to five pairs of prolegs; as they grow, these larvae change in appearance, going through a series of stages called instars. Once matured, the larva develops into a pupa. A few butterflies and many moth species spin a silk case or cocoon prior to pupating, while others do not, instead going underground. A butterfly pupa, called a chrysalis, has a hard skin with no cocoon. Once the pupa has completed its metamorphosis, a sexually mature adult emerges; the Lepidoptera have, over millions of years, evolved a wide range of wing patterns and coloration ranging from drab moths akin to the related order Trichoptera, to the brightly colored and complex-patterned butterflies. Accordingly, this is the most recognized and popular of insect orders with many people involved in the observation, collection, rearing of, commerce in these insects.
A person who collects or studies this order is referred to as a lepidopterist. Butterflies and moths play an important role in the natural ecosystem as pollinators and as food in the food chain. In many species, the female may produce from 200 to 600 eggs, while in others, the number may approach 30,000 eggs in one day; the caterpillars hatching from these eggs can cause damage to large quantities of crops. Many moth and butterfly species are of economic interest by virtue of their role as pollinators, the silk they produce, or as pest species; the term was coined by Linnaeus in 1735 and is derived from Greek λεπίς, gen. λεπίδος and πτερόν. Sometimes, the term Rhopalocera is used for the clade of all butterfly species, derived from the Ancient Greek ῥόπαλον and κέρας meaning "club" and "horn" coming from the shape of the antennae of butterflies; the origins of the common names "butterfly" and "moth" are varied and obscure. The English word butterfly is with many variations in spelling. Other than that, the origin is unknown, although it could be derived from the pale yellow color of many species' wings suggesting the color of butter.
The species of Heterocera are called moths. The origins of the English word moth are more clear, deriving from the Old English moððe" from Common Germanic, its origins are related to Old English maða meaning "maggot" or from the root of "midge", which until the 16th century was used to indicate the larva in reference to devouring clothes. The etymological origins of the word "caterpillar", the larval form of butterflies and moths, are from the early 16th century, from Middle English catirpel, catirpeller an alteration of Old North French catepelose: cate, cat + pelose, hairy; the Lepidoptera are among the most successful groups of insects. They are found on all continents, except Antarctica, inhabit all terrestrial habitats ranging from desert to rainforest, from lowland grasslands to mountain plateaus, but always associated with higher plants angiosperms. Among the most northern dwelling species of butterflies and moths is the Arctic Apollo, found in the Arctic Circle in northeastern Yakutia, at an altitude of 1500 m above sea level.
In the Himalayas, various Apollo species such as Parnassius epaphus have been recorded to occur up to an altitude of 6,000 m above sea level. Some lepidopteran species exhibit symbiotic, phoretic, or parasitic lifestyles, inhabiting the bodies of organisms rather than the environment. Coprophagous pyralid moth species, called sloth moths, such as Bradipodicola hahneli and Cryptoses choloepi, are unusual in that they are found inhabiting the fur of sloths, mammals found in Central and South America. Two species of Tinea moths have been recorded as feeding on horny tissue and have been bred from the horns of cattle; the larva of Zenodochium coccivorella is an internal parasite of the coccid Kermes species. Many species have been recorded as breeding in natural materials or refuse such as owl pellets, bat caves, honeycombs or diseased fruit; as of 2007, there was 174,250 lepi