He works at its Museum of Comparative Zoology. Most crustaceans live in the water, Farrell points out. But some woodlice, also called rollie pollies, dwell on land. You probably know the two main types of myriapods: millipedes and centipedes.
Myriapods live on land and most have lots of legs. These fangs are not chelicera. Centipedes instead eat with mandibles, as crustaceans and insects do. But they also have a pair of venomous, fang-like legs. Millipedes, in contrast, are herbivores. So millipedes are much slower than centipedes. There are more species of insects on land than all other arthropods combined, says Kip Will. Bees fly, beetles crawl like tiny armored tanks and the Australian walking stick has camouflaged itself to look like a leaf mixed with a scorpion.
Different as insects can be, pretty much all of them have six legs and the same three body parts — head, thorax and abdomen. It might be due to the world they live in.
Their small size, Will says, means insects see the world differently from us. That group includes stinkbugs and bed bugs. Why most animals are insects. Insects are arthropods. Arthropods are characterised by having the following features: a hard external skeleton called a exoskeleton a segmented body at least three pairs of jointed legs The Arthropoda is divided into a number of classes.
Insect are successful and important The insects have proved to be the most successful arthropods. Close Modal Dialog. Stay in the know Get our monthly emails for amazing animals, research insights and museum events. Sign up today. Insect classification Modern insect classification divides the Insecta into 29 orders, many of which have common names.
Some of the more common orders are: Mantodea - praying mantids Blattodea - cockroaches Isoptera - termites Siphonaptera - fleas Odonata - dragonflies and damselflies Dermaptera - earwigs Diptera - flies Lepidoptera - butterflies and moths Orthoptera - grasshoppers, katydids, crickets Coleoptera - beetles Hymenoptera - wasps, bees, ants, sawflies. The insect body. Insect features The insect body is divided into three main parts, the head, thorax and abdomen. Insects have no internal skeleton, instead they are covered in an external shell exoskeleton that protects their soft internal organs.
No insect has more than three pairs of legs, except for some immature forms such as caterpillars that have prolegs. These are appendages that serve the purpose of legs. The typical insect mouth has a pair of lower jaws maxillae and upper jaws mandibles which are designed to bite.
There are many variations to this structure, as many moths and butterflies have tubular sucking mouthparts, many bugs and other blood-sucking insects have sucking stabbing mouthparts and some adult insects simply don't have functional mouthparts. Insects have one pair of antennae located on the head Most insects have one or two pairs of wings although some insects such as lice, fleas, bristletails and silverfish are completely wingless. Together these features can help us distinguish insects from other arthropods.
Insect evolution. Types of insects. Moths and butterflies The scale-winged insects, Order Lepidoptera. Moths, butterflies and skippers: Order Lepidoptera What are the differences between butterflies and moths? Butterfly and moth sketches by the Scott family. Ants, wasps, bees and sawflies The heavy-winged insects, Order Hymenoptera.
This includes places such as leaf litter and soil and beneath bark and stones. A few are occasionally pests of cultivated plants, but they usually feed on organic debris. Those that can roll into a ball are called pillbugs or roly-polys; those that can not form a ball are the sowbugs. Class Arachnida uh-rak-nid-uh , spiders, ticks, mites, scorpions and others. This is a diverse class which belongs to a subphylum of the Arthropoda known as the Chelicerata. Chelicerata are characterized as having two distinct body regions, a cephlothorax and an abdomen.
Chelicerates have six pairs of appendages, the first two pairs being mouthparts and the following four pairs being legs. They do not have antennae. The first pair of mouthparts are the chelicerae sing.
They are three-segmented and pincher-like. In spiders, the terminal third segment is often called a fang. The second pair of mouthparts are the six-segmented pedipalps. They may appear leg-like spiders or claw-like scorpions. The legs of most Chelicerata have seven segments.
Compared to insects, whose legs have six segments, there is an extra segment, called the patella, between the third segment the femur and the fourth segment the tibia. Common orders of Arachnida include:. Order Araneae a-ran-e-uh , the spiders. No antennae. Abdomen joined to cephlothorax by slender pedicel. Four pairs of legs. Mouthparts: One pair chelicerae and one pair of pedipalps.
Eyes simple ocelli. Usually eight, sometimes fewer. Poison apparatus opens on the fangs of the chelicerae. Silk apparatus always present at end of abdomen, below anus. This is a large order, having about species in North America. Although nearly all spiders have venom glands, spiders seldom bite man.
Only a few U. In Nebraska, the black widow and the brown recluse are the only seriously venomous spiders. Order Acari ak-a-ri , the mites and ticks. Abdomen broadly joined to cephlothorax no pedicel. Four pairs of legs in adults; only three pairs at hatching. Ticks and mites occur just about anywhere animal life is found. They may be terrestrial or aquatic, free-living or parasitic.
They may feed on organic debris beneficial scavengers or on living plants or animals. Some of the plant feeders are serious pests of crops. Some of the parasitic forms are pests of animals and man. Some are vectors of diseases. A few of the predatory and parasitic mites are considered beneficial because they feed on insects or other pests.
Over 30, species of ticks and mites have been described. Order Scorpiones scor-pi-on-es , the scorpions. No pedicel between cephlothorax and abdomen. Four pairs of legs on cephlothorax. One pair of chelicerae and one pair of long, pincher-like pedipalpsAbdomen with seven broad segments anteriorly, followed by five narrower segments which end with a large stinger. Scorpions feed mostly on insects and spiders which they catch with their pedipalps. They may or may not sting their prey.
Scorpions do not ordinarily attack man, but they will sting if disturbed or cornered. Of the forty-some species that occur in the U. One Arizona species, however, is very venomous, and its sting can be fatal. Class Chilopoda chi-lo-po-da , the centipedes. Two tagmata head and trunk One pair of antennae with 14 or more segments. Mouthparts: one pair of mandibles and two pairs of maxillae. Appendages on the first trunk segment are clawlike poison jaws or fangs with which centipedes paralyze their prey.
The class name refers to the lip- like appearance of the fused bases of these appendages.
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