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What are insects? Sometimes people might take the misconception that spider is a kind of eight-leg-insect. If you think so, it's t ime for you to learn more! Now, let's take a look at the classification of insects.
In the field of biological classification , insects are grouped under Class Insecta, phylum Arthropoda, which is the largest phylum in Kingdom Animalia. In phylum Arthropoda, insects are the unique group that are winged and capable to fly.
Let's study to the word "insect". The word "insect" came from the Latin insectum , the prefix " in" means "above" and " sectum" has the denotation of "to cut in". Integrating those meanings then "insect" means many segments.
Adult insects have a segmented body, divided into a head, thorax and abdomen. They also have the following characteristics: a head with a pair of antennae, a pair of compound eyes, 0-3 ocelli, and mouthparts; thorax with 3 pairs of legs, wingless or usually two pairs of wings; a genital opening at the end of abdomen. Besides, the insect has a tracheal system for respiration, and a main excretory organ called Malpighian tubules.
Spiders, for instance, have eight legs and their body is divided into two parts: the cephalothorax and the abdomen. These characteristics are quite different from that of insects, so spiders are not insects. Spiders are also the members of Arthropoda but belong to class Arachnida, which makes them relatives of insects.
insect |
not insect |
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Lepidoptera |
spider |
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Classification of Insects |
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There are around one million discovered and described species of insects worldwide. It is estimated that at least some 30-80 million species of organisms yet to be discovered or named , because many places have not been investigated. As presum ing that insects account for over 50% of all species on the Earth. Why is there such a diversity of insects? The answer lies in their ability to adapt to various environments by developing various structures and behaviors through long-term evolution by natural selections. The characteristics they have developed include small body size, exoskeleton, flight, metamorphosis, complicated sensory and nervous transmitting systems, high reproductive rate and short generation time.
How we classify such a high ly divers e species? In the past, various hierachical classifications were adopted by scientists with different viewpoints. At present, with adva nce in technology, more evidences support that orders Protura, Collembola and Diplura should be removed from Insecta and form two cla sses: that is, Class Parainsecta incorporating Protura and Collembola, and Class Entognatha formed by Diplura independently. T hese two new Classes and Class Insecta combined are called Hexapoda. However, if the generalized definition of insect that Arthropoda encompasses with three pairs of legs , Protura, Collembola, and Diplura will still be included in the class of Insecta. Base on strict definition , Class of Inseta excludes the three o rders and divided into two subclasses of Apterygota and Pterygota, representing 30 orders in total. The strictly define d classification categories including order characteristics are listed as below.
Heapoda |
Protura |
Collembola |
Diplura |
Insecta |
Apterygota |
Archaeognatha (Members of the order were once grouped under Thysanura) |
Thysanura (This is the narrowly defined Thysanura, which excludes archaeognathans) |
Pterygta |
Palaeoptera |
Ephemeroptera |
Odonata |
Neoptera |
Exopterygota |
Grylloblattodea |
Mantodea |
Isoptera |
Blattodea |
Dermaptera |
Plecoptera |
Embiidina |
Orthoptera |
Phasmatodea |
Zoraptera |
Psocoptera |
Phthiraptera (This order comprises members of Mallophaga and Anoplura) |
Hemiptera (This order comprises members of Hemiptera and Homoptera) |
Thysanoptera |
Mantophasmatodea |
Endopterygota |
Megaloptera |
Raphidioptera (Members of this order were once grouped under Neuroptera in traditional scheme) |
Neuroptera |
Coleoptera |
Strepsiptera |
Mecoptera |
Diptera |
Siphonaptera |
Lepidoptera |
Trichoptera |
Hymenoptera |
Order/Class |
Common Name |
Characteristics |
Photo |
Protura |
Proturans |
Proturans are small and soft-bodied insects that inhabit soil. They lack compound eyes and feed on fungi. There are more than 20 species known at the moment in Taiwan. It is estimated that Taiwan has at least 60 species. |
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Collembola |
Springtails |
Springtails are small-sized insects that can spring by using their forked organ (furcula) at the end of their abdomen. Springtails are primarily scavengers but some also feed on pollen and algae. Most springtails are terrestrial with only few living on the surface of fresh water and seawater. It is estimated that Taiwan has more than 150 species of springtails. |
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Diplura |
two-pronged bristletails |
Two-pronged bristletails are small to medium-sized, long, slender, terrestrial and without compound eyes. Most species live under stones, in soil, dead wood or leaf litter. They have a distinct pair of cerci at the end of the abdomen. There are more than 30 species of them in Taiwan. |
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Archaeognatha |
Bristletails |
Bristletails are spindle-shaped with thorax arched dorsally and tapered posteriorly. Their antennae are filiform and multisegmented. Maxillary palpi are seven-segmented. Their bodies are usually covered with scales. Their compound eyes are large and connected to each other. They have two short multisegmented cerci and a long median caudal filament on the abdomen. They are swift movers and jumpers, feeding as scavengers. Most bristletails live in shadowy places, such as on mosses and lichens or in rock crevices. |
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Thysanura |
Silverfishes |
Silverfishes have spindle-shaped, dorsoventrally flattened and often scaly bodies. Their compound eyes are vestigial or small. Maxillary palpi are five-segmented. Two cerci and one median caudal filament on the abdomen are of the same length. Silverfishes are swift mover, feeding as scavengers. They are found in human dwellings and dark, damp places in the wild. |
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Ephemeroptera |
Mayflies |
Mayflies go through an aquatic nymph stage and two adult stages (the subimago and the imago). Adult mayflies are soft-bodied, with short antennae. Their mouthparts are reduced so they do not feed. Their forewings are large while hindwings are rather small and rounded. They have long cerci and a median caudal filament at the end of the abdomen. There are around 62 species of mayflies in Taiwan. |
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Odonata |
Dragonflies, damselflies |
Immature dragonflies and damselflies (naiads) are aquatic while adults are terrestrial. The adults have a big mobile head with large compound eyes and short antennae. They have a vestigial, neck-like prothorax and two pairs of wings, which are net-veined and almost equal in size. According to Lieftinck et al. (1984), 135 species and subspecies belonging to 78 genera, 14 families have been recorded in Taiwan. |
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Blattodea |
Cockroaches |
Cockroaches are dorsoventrally flattened and have filiform antennae and well-developed compound eyes. Their head is concealed under the prothorax. The Mesothorax and metathorax are poorly developed. Forewings are thickened while hindwings are membranous and folded beneath the forewings. They are found in human dwellings. They also live outdoors and prefer dark places, such as caves, dead branches or leaf litter. There are around 75 recorded species of Blattodea in Taiwan. |
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Mantodea |
Praying mantes |
Praying mantes have a mobile triangular head with large compound eyes. Their elongated prothorax looks like a long neck. The two forelegs are specialized into a pair of sickle-shaped feet for catching small insects. They have two pairs of wings. Forewings are slender and thickened while hindwings, large and membranous. A mantis egg case is called an ootheca. |
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Isoptera |
Termites |
Termites are pale-colored, soft-bodied, with bead-like moniliform antennae and large and round compound eyes. Some are winged and some are wingless. Those winged have two pairs of membranous and slender wings. Forewings and hindwings are all similar in shape and size. Termites are gregarious insects with a caste colony structure. There are around 16 known species in Taiwan but the actual number of species occurring is likely to be higher. |
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Grylloblattodea |
Rock crawlers, icebugs |
Adult rock crawlers have a cylindrical body covered with tiny hair. They have filiform antennae and small or no compound eyes. They are wingless. Terga of prothorax, mesothorax and metathorax are similar in shape and mobile. They have long and segmented cerci at the posterior end of the abdomen. They are found in caves or on ice or snow in areas of lower temperatures. They have never been found in Taiwan. |
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Dermaptera |
Earwigs |
Earwigs are elongated and dorsoventrally flattened insects. The head is prognathous, flattened and with obvious Y-shaped epicranial suture. The compound eyes are present or absent. No ocelli. The antennae are filiform. The pronotum is nearly quadrangular. The forewings are short and leathery while the hindwings are large and membranous, with radically arranged veins, and folded under the forewings when at rest. There are thick and strong cerci at the posterior end of the abdomen. Earwigs are omnivorous and usually wander around at night and hide in soil or under rocks during the day. There are around 42 recorded species in Taiwan. |
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Plecoptera |
Stoneflies |
Naiads are aquatic and often dwell in waters of high oxygen concentration. Adults have a soft body and a wide head with well-developed compound eyes. Their wings are folded horizontally back over the thorax and abdomen when at rest. The prothorax is large and mobile. |
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Embiidina |
Web spinners |
Web spinners have an elongated and narrow body. The compound eyes are small and reniform. No ocelli. The antennae are long and filiform. Foretarsi are enlarged at the base and contain silk gland. There are two recorded species in Taiwan. At present, the taxonomy of this order is not studied on the island. |
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Orthoptera |
Locusts, katydids, crickets |
Orthopterans have an elongated body and well-developed compound eyes. The pronotum is saddle-shaped or shield-shaped. Forewings consist of tegmina. The hindwings are large. Enlarged hind femurs are used for jumping. Orthopterans have a short pair of cerci at the posterior end of the abdomen. In Taiwan, there are around 41 different families of crickets, encompassing 18 species of Trigonidiidae and 14 species of Nemobiidae. |
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Phasmatodea |
Stick insects |
Stick insects have a cylindrical or leaf-like body, which is usually cryptically colored. The pronotum is short. The wings are present or absent. The forewings are narrow, thick and sturdy. Legs are long. There are 10 genera and 27 species of stick insects recorded in Taiwan. |
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Zoraptera |
zorapterans |
Zorapterans are fragile and small in size and have sexual dimorphism. Some have vestigial compound eyes and no wings while some have darkly pigmented compound eyes and two pairs of wings. They have 9-segmented antennae and a short pair of cerci at the posterior end of the abdomen. There is only one species found in Taiwan now. |
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Psocoptera |
Booklice, barklice |
Psocopterans have an enlarged postclypecus on the large head with huge compound eyes and filiform antennae. When at rest, the wings held roof-like over back. The thorax humped in side view. The brachypterous and apterous forms are common in this order. According to Chou (1997), there are 66 recorded species on the island. |
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Phthiraptera |
Sucking lice, Chewing lice |
Phthirapterans are external parasites. They are dorsoventrally flattened, wingless, with chewing or sucking mouthparts, small or no compound eyes. The antennae are short and sturdy. The legs are short and strong. The tarsi and claws are adapted to gripping the hair of their hosts. There are around 17 recorded species in Taiwan, but the taxonomy of this order is not studied presently. |
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Hemiptera |
True bugs, aphids, cicadas, plant hoppers, leaf hoppers, jumping plant lice |
Hemipterans have piercing-sucking mouthparts and two pairs of wings. The forewings are toughened with few membranous areas or completely membranous. |
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Thysanoptera |
Thrips |
Thrips are small and slender insects with short antennae. The compound eyes are protruding, round or reniform. They have rasping-sucking mouthparts. They are winged or have reduced wings. The two pairs of wings are narrow and haired marginally. The tarsi have bladders between claws. Thysanoptera are divided into two suborders, Terebrantia and Tubulifera. There are more than 200 recorded species in Taiwan. |
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Megaloptera |
dobsonflies |
Dobsonflies have well-developed compound eyes, filiform antennae and well-developed mandibles. The two pairs of wings are similar in size. The hindwings have large anal lobes. When at rest, they hold their wings roof-like over their body. Their larvae are aquatic. |
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Raphidioptera |
Snakeflies |
The insects in this order have a flattened head, elongated prothorax and filiform antennae. Ocelli are present or absent. The two pairs of wings are similar in size. Female has a conspicuous ovipositor. |
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Neuroptera |
Lacewings, antlions, owl flies |
Neuropterans have filiform antennae and conspicuous compound eyes. Ocelli are present or absent. The two pairs of wings are similar in size and held rooflike when at rest. The wings have reticulated venation with main vein forked abundantly along the leading edge. There are around 120 recorded species in Taiwan. Green lacewings are popular biocontrol agents used as natural enemies against pests. |
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Coleoptera |
Beetles |
Beetles'antennae usually have less than 11 segments. No ocelli. The prothorax is usually large and conspicuous. Their forewings are hardened into elytra and connected at the center. The hindwings are mostly membranous. There are more than 375,000 named species worldwide. |
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Strepsiptera |
Stylops |
Adults show sexual dimorphism. Adult females are endoparasitic in their hosts and have no compound eyes, antennae, mouthparts, legs and wings. Adult males are free-living and have branched antennae, reduced and club-like forewings, and large and fan-shaped hindwings. |
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Mecoptera |
Scorpionflies |
Scorpionflies are slender insects. They have an extended head with beak-like mouthparts near its tip. They have filiform antennae, large compound eyes, and two pairs of large and narrow wings. Some species are short-winged or wingless. |
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Diptera |
Flies, mosquitoes, horseflies, blackflies |
Dipterans have a mobile head, large compound eyes and three ocelli. The forewings are membranous while the hindwings are reduced into a small pair of halteres. The mesothorax is enlarged because of developed flight muscle. There are 83 families and 2,748 species of Dipterans in Taiwan. |
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Siphonaptera |
Fleas |
Fleas are small and bilaterally flattened and hardened insects. Their antennae are very short and recessed in grooves on the head. They have piercing and sucking mouthparts. The compound eyes are as simple as ocelli.Comblike structures are pesent around the head and the first thoracic tergite. They have many spines and bristles. The hind femurs are enlarged for jumping. Siphonaptera is a smaller order in Insecta. There are around 2,500 species or subspecies worldwide. In Taiwan, there are about 6 families, 21 genera and 31 species of them. Fleas can transmit black death, endemic typhus, tapeworm disease and other diseases that are transmittable between human and animals. |
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Lepidoptera |
Butterflies, moths |
Their body and wings are often covered with microscopic scales or hairs. They have large compound eyes and Siphoning type of mouthparts. According to 'Lepidoptera of Taiwan,' published in 1992, there are around 94 families and 3,976 species under this order. It also estimates Taiwan has about 5,000 species of Lepidoptera. |
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Trichoptera |
Caddisflies |
Caddisflies have a slender body, large compound eyes, filiform antennae and reduced mouthparts. Ocelli are present or absent. The body and wings are covered with hairs. The wings are similar in size and held rooflike when at rest. There are 27 families, 62 genera and 178 species of them in Taiwan. |
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Hymenoptera |
Bees, ants |
Hymenopterans have filiform antennae, well-developed compound eyes and two pairs of membranous wings. The wings are connected by a series of interlocking hooks when in flight. The members in suborder Apocrita have a constricted waist formed by the front part of the abdomen. The taxonomy of Hymenoptera is seldom studied in Taiwan. There are around 2,790 species known on the island, accounting for only 2.5% of species worldwide, but the exact number of species should be much higher. |
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Mantophasmatodea |
Gladiators |
Mantophasmatodea is a new insect order of insect just found in 2002. The members of this order look like praying mantids, stick insects, or grasshoppers. They are wingless, with has longer antennae and carnivorous. Body length of adult is about 2-3cm. It is distributed in South Africa. |
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Flow Chart of Insect Collection Management |
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The flow chart of insect collection management in NMNS ENT.
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Features of Insects and Eriophyoidea Collections |
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A hoverfly resting on the leaf. |
A true bug exhibiting metallic luster. |
The current task of Section of Entomology focuses on insect and mites collections from Taiwan and will gradually expand to include collections from the Asia Pacific region and other parts of the world. The section has placed particular emphasis on collection of specimens from the orders of Lepidoptera and Homoptera and maintains collections of p inned specimens, slide-mounted specimens, frozen specimens, alcohol-preserved specimens, nest specimens and gall specimens. At present, the whole collection contains nearly 400,000 specimens, including those retrieved from Malaise traps set up from mid-elevations to high-elevations in Taiwan, Bao-Sing Chang's collections and specimens acquired during insect surveys in Lanyu area.
Presently, the section has five researchers. Their work focuses on the taxonomy of Sphingidae , Pyralidoidea ( Lepidoptera) , Psocoptera, Miridae ( Heteroptera) and eriophyoid mites. They also study interaction between insects and plants, including host plants of l epidopterans; ecology of adult insects and larvae; ecology of eriophyoid mites and their host plants; pest monitoring for museums; pest monitoring for greenhouses of botanical gardens; researches on the physiology and chemoecology of insects. Visiting researcher Dr. Man-Miao Yang is doing researches on galls and gall biology as well as collecting gall specimens . Another visiting researcher Dr. Yu-Feng Hsu is doing researches on phylogeny, biogeography and conservation biology of butterflies. There are one technician to assist in the collection, rearing and cateloging of insect specimens and 14 volunteers to help with the specimen management, including specimen preparation, preliminary sorting , data transcription and computer data entry. At times when full-time human resource is insufficient, these people have provided indispensable impetus for the advancement of the section.
In addition to specimens, the section also collects published literature pertaining to new species found in Taiwan and related identification publications and data informations relating to type specimens of Taiwan. Besides, it also exchanges specimens and related informations with others worldwide. By so doing, the division purposes to become an information center of Taiwan's insect specimens and literature, hoping to attract more people to use museum resources in support of their research.
With the help of Computer Science Division, the Section of Entomology established the Insect Collection and Data Management System and has since been able to manage and use collections and specimen-associated data in a more efficient setting. The multifunctional system allows staff to store and modify specimen-associated data and literature, print labels, conduct statistics, make inquiry and print reports etc. .. Presently, around 32,000 record entries about 100,000 specimens have been made and will be on -lin e for the use of other research institutions. The Taiwan Digital Archives program is under way, digitalizing the type specimens and important specimens maintained by the section . In the future, more data and literature pertaining to type specimens of local insect species and other important specimens will be collected and digitalized, allowing more people to use them on-line.
In addition to collection and research work, the researchers of the section often support exhibition and education activities in due time. They provide exhibition materials and specimens, write or review articles, and answer visitors' queries. They also give speeches, train museum guides and assist in the design of teaching plans and activities in line with science education and exhibition activities.
The science education and exhibition tasks that have been completed include "Taiwan's Butterflies," a long-distance teaching program, "Butterfly's Ecology," an element of the on-line Digital Museum program, and "Mega-Insects Park" and "Bugs Park," a special exhibition launched by the Museum. |
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