Arthropods - insect, spiders, crustaceans, & myriapods
Review - kingdom, phylum, class, order, family genus, species
Overview
Introduction
This page includes information for the study of the arthropod phylum, its classes and orders. It includes fact sheets for arthropods: insects, arachnid, crustaceans, myriapod, and chilopoda. Comparison of spiders and insects, keys to identify insects, suggestions for collecting insects, an outline of study or activity sequence, and sample assessments.
The arthropoda (phylum) includes animals which are particularly notable for their head appendages. They also have bilateral symmetry, segmented body parts, hard exoskeletons, jointed legs, and many pairs of legs. They include:
- Insect (Hexapoda - class) has segmented bodies, jointed legs, an exoskeleton and three body regions. Which include the
- Head with mouth parts, eyes, and antennae.
- Thorax with three pairs of legs and usually 1-2 pairs of wings.
- Abdomen with many segments and includes the digestive, excretory, and reproductive systems.
- Arachnid (Chelicerata - class) includes spiders, ticks, mites, and scorpions. These animals have two body parts, eight legs, and do not have wings or antennae.
- Crustacea or crustaceans (class) include sow bug (also called pill bugs and roly-poly) shrimp, crayfish, crabs, horseshoe crabs, lobsters, and barnacles. They have two body regions, 10 or more legs, two pair of antennae, a segmented body, hard (chitinous - like a grasshopper) exoskeleton, paired jointed limbs, and no wings.
- Myriapoda used to include the following classes which are now separate classes:
- Diplopoda include millipedes (class) have worm like elongated bodies, with many segments, two pairs of legs on each segment, and one pair of antennae or none. Most are herbivorous, shun light, living in the soil or under stones and logs.
- Chilopoda include the centipede with worm like bodies, segmented bodies, one pair of legs on each body segment and one pair of antennae or none.
- Pauropoda similar to centipedes. They are small soft-bodied animals with one pair of legs per segment
- Symphyla like centipedes. Are small eyeless animals with one pair of legs per segment, typically living in soil and leaf mold.
Classes Insecta (Hexapoda) - facts
Insect (class hexapoda) have segmented bodies, jointed legs, an exoskeleton and three body regions.
- Head which includes the mouth parts, eyes, and antennae.
- Thorax which has three pairs of legs and usually 1-2 pairs of wings.
- Abdomen which is many segments and includes the digestive, excretory, and reproductive systems.
Insects are useful for pollination, produce useful substances like honey, silk, wax, dyes, and pigments. They control other pests, are scavengers, provide food, and are used in genetic studies. Four-fifths of all animals on the Earth are from this class. There are over one million species of insects. There may be from 500-2000 insects on one square meter of land. This make a total of 4,000,000 on one acre.
Insects have many harmful effects. One of the most recognized is the damage they do to crops. They eat millions of dollars of crops every day. As incredible as this seems, most insects will feed only on certain plants and some only on one variety. One example of an insect that has been in Nebraska for millions of years and not done much damage until recently is the Colorado potato beetle. This insect normally feeds on the buffalo burr plant, but has adapted to feed on potatoes. This is bad news for the potato growers and good news for the buffalo burr.
Besides eating crops insects spread disease. Flies infect many animals. The screw worm infects cattle, the mosquito infects humans with sleeping sickness, yellow fever, malaria, and encephalitis. Fleas infect people with bubonic plague and lice with typhus. Some insects also harm humans by stinging and may cause allergic reactions.
The different growth changes an insects pass through are called metamorphosis (change in form). There are four types of metamorphosis.
- Growth without metamorphosis is when the young insect looks exactly like the adult form when it is hatched from the egg. Insect orders of this type include thysanura (silverfish and firebrats), collembola (springtails), mallophaga (chewing lice), and anoplura (sucking lice). The three growth changes are called egg, young, and adult.
- Gradual metamorphosis is where insects change shape gradually through three stages, with each stage looking more like the adult. Orders of this type include orthoptera (grasshoppers, crickets, preying mantids, walking sticks, and cockroaches), isoptera (termites), corrodentia (book lice), thysanoptera (thrips), hemiptera (true bugs), homoptera (scales, cicadas, and aphids), and dermaptera (earwigs). The three stages are egg, nymphs, and adult.
- Incomplete metamorphosis is where the insects change shape gradually but do not look like adults until they shed their last skin, then they change fast. Orders of this type include ephemeroptera (May flies), odonata (dragon and damsel flies), and plecoptera (stonefly). The three stages are called egg, nymph, and adult.
- Complete metamorphosis is when the insect changes shape through four stages of growth. The young do not look like the adult and there is a great change in shape from the pupa stage to the adult stage. Orders of this type include neuroptera (aphid lions, ant lions, dobson flies), coleoptera (beetles), strepsiptera, mecoptera (scorpion flies), tricoptera (caddis flies), lepidoptera (butterflies and moths), diptera (flies), siphonaptera (fleas), and hymenoptera (bees, wasps, and ants).The four stages are the egg, larvae, pupa, and adult.
Insect eggs vary greatly in color and shape. Only a few may survive from masses of a thousand or more deposited.
The embryo usually develops from a fertilized egg but in some cases (wasps and bees) the unfertilized egg produces a male.
The caterpillar bites its way out of the egg. The flea has a hatching spine that splits open the shell.
Larvae must store enough energy to become an adult. Some types of larvae are caterpillars, grubs, wire worms, and maggots.
The pupa is the resting stage of the insect before it becomes an adult. In this stage there may be a cocoon, a case that looks like a seed, or it may have a small immature bug like shape.
Insects protect themselves by secreting poison, stinging, and protective coloration. Insects control their body temperature by how they position themselves relative to the sun. A temperature of 38 -40 degrees Celsius is necessary for them to warm their wings for optimum flight.
Insect (orders)
- Coleoptera - beetles
- Lepidoptera - butterflies and moths
- Hymenoptera - bees, wasps, and ants (Early grade activity - make a bee model and explore pollination)
- Diptera - flies
- Orthoptera - grasshoppers, crickets, preying mantis, walking sticks, and cockroaches
- Hemiptera - true bugs
- Homoptera - scales, cicadas, and aphids
- Odonata - dragon and damsel flies
- Mallophaga - chewing lice
- Tricoptera - caddis flies
- Neuroptera - aphid lions, ant lions, and dobson flies
- Siphonaptera - fleas and mosquitoes
- Corrodentia - book lice
- Ephemeroptera - may flies
- Dermaptera - earwigs
- Thysanoptera - thrips
- Anoplura - sucking lice
- Mecoptera - scorpion flies
- Collembola - springtails
- Thysanura - silverfish and firebrats
- Isoptera - termites
Spiders (Arachnids) - facts
Spiders (class Chelicerata or arachnid) include spiders, ticks, mites, and scorpions. They have two body parts, eight legs, and do not have wings or antennae.
The word spider is related to the Old English word spinnan which means to spin. While most people associate spiders with spinning webs wandering spiders build none at all. They do use silk in other ways.
Most spiders release a line of thread as they walk called a drag line. As they move they attach the drag line to the surface on which they walk. If they happen to fall or jump they are supported by the line.
The spider also uses the silk to wrap its prey, build a nest for eggs; molting; hibernating; or to rest in a protected area, females use it to make egg sacs, and males to make sperm webs. The most familiar use of webs is for snares. Snare webs are made as sheet webs, funnel webs, orb webs, and combinations of theses. Another interesting use of the web is as a flotation device. The spider climbs on a plant and releases threads from its spinnerets and when there are enough to support the spider it will let go of its support and float away in the air.
The eggs are always laid in silk and the number of eggs varies from one to two, 25-30, and 100-300 in most. Once there were 2652 counted in one sac. Some spiders make more than one sac and some up to as many as twenty or more.
Spiders molt (shed their outer covering) as they become older. If they loose a leg they may be able to regenerate it if the molt is not too near. The regenerated leg will be somewhat smaller than normal.
Spiders are carnivorous and are attracted to the movement of their prey. Most live on insects. There are two ways spiders ingest their food. Those with weak jaws puncture the body of the insect with their fangs and then inject digestive juices into this hole and suck the digested liquid back into their body until there is only an empty shell left. The tarantulas, wolf spider, large orb weavers, and others with strong jaws mash the insect to a pulp with their jaws and regurgitate the digestive juices over it. Ingesting the digested material.
Most spiders can survive long periods of fasting and many can go long periods without water. However, some species may die if deprived of water for only a few days. Spiders may feed on other spiders and this tendency of cannibalism does not make them a social animal.
The male spider will wander to find a mate. When he meets a female he will many times dance to attract her attention. It is not true that the female will always kill the male and eat him. This is only happens in very few species. In some species the male will leave and seek another mate. In some cases the male will stay and share the same web for a period of time. The male can be expected to die sooner than the female and even though many females die soon after laying their eggs some species will live two or three years more after laying their eggs.
Spiders have been found almost everywhere. Near water, in or on top of the ground, from caves to the top of mountains (Mount Everest 22,000 feet) and some have actually been collected 5000 feet in the air from planes. The number of spiders per acre has been found in one instance to be 407,000 in a clay meadow and 2,200,000 in a grassy field.
More spider & insect information
Comparison of spiders and insects characteristics:
| Spider | Insect | |
|---|---|---|
| Body region | two | three |
| Antennae | none | one pair |
| Legs | four pair | three pair |
| Pedipalps | one pair six segments | none |
| Poison apparatus | on fangs | If present on abdomen |
| Wings | none | most adults have |
| Eyes | Simple ocelli commonly 8-6 | compound plus some have 2-3 ocelli |
| Silk apparatus | always present on the end of the abdomen | only in some larvae at the lower lip |
| Food digestion | always before swallowing by regurgitation | usually after swallowing |
| Development | direst no larval stage spiderlings look like parents | may have metamorphosis with larval and pupa stage or nymphs |
Arthropod classification check list
| Animal | Bilateral symmetry | Segmented body | Exoskeleton | Leg joints | Pairs of legs | |
|---|---|---|---|---|---|---|
| Spider | ||||||
| Tick | ||||||
| Fly | ||||||
| Dog | ||||||
| Centipede | ||||||
| Pill bug | ||||||
| Lego
Exo-Force, Supernova, or Bionicle |
||||||
| Enter one of your own | ||||||
| Enter another of your own |
Insect & spider container
Spider & egg sacs
Spider island
Collecting insects
Insects can be collected with a net and transferred to a collection jar to be observed or to plastic bags to be placed in a freezer to be killed for mounting, or to a killing jar. If a grassy field, tree, or shrub is swept with a net, by quickly swinging the net in a figure 8 over the plants, then it is easier to tranfer the insects to a large plastic bag and deal with them there than inside a net. Source for more information on collecting.
While insects may be collected all year, they are most numerous during the warm days of spring, summer and fall. Places to find them include:
Places to find insects:
- Around flowers for butterflies, moths, and bees.
- Under rocks and boards for beetles and many other kinds.
- On trees and shrubs for leaf hoppers, treehoppers, and leaf beetles.
- On fermenting fruits for many kinds of bees, beetles, and butterflies.
- Dead animals for scavenger beetles.
- In the vegetable garden for the many garden pests and beneficial insects.
- Legumes for bugs and bees.
- Corn for rootworm beetles, corn borers, aphids, and aphid lions.
- Grasses and weeds have a great variety that can be collected with a sweep net.
- Do not overlook the insects that live in the home, in water, or on animals.
Mounting insects suggestions
When insects become dry, they need to be relaxed so they will not break, before they are manipulated and pinned.
Relaxing jar
To relax dried insects place a bit of cotton or blotting paper in the bottom of a pint jar. Moisten the cotton or paper with water and add a drop or two of Lysol to prevent mold. Place insect specimens in this jar for two days, or until they have become relaxed so that the legs, body, and wings may be moved without breaking.
Pinning insects
Most insects are pinned directly through the body using a special insect pin. A county agricultural agent can provide a source for insect pins as well as other valuable information.
The place of pinning depends upon the type of insect. The diagram shows methods of pinning different orders of insects.
Very small insects should be glued to small cardboard triangles which may be made or obtained from an extension entomologist or your county agent.
The distance from the head of the pin to the body of the insect should be the same on all specimens. This can be measured with a pinning block. First place the pin through the body of the insect to within 1/4 inch of the head of the pin. Then place the head of the pin in the hole of the shortest section of the pinning block to measure the distance from the pin head. The next 1/4 inch sections are for label spacing.
Labeling insects
Itis customary to place two labels on the pin below the specimen.
The top label identifies the county where the specimen was collected, the date it was collected, and the name of the collector.
The lower label has the order of the insect.
Spreading boards
The wings of butterflies and moths should be spread before they dry.
This preserves them in a position most attractive for displays.
Place the body of the butterfly or moth (or other insects if you wish) in the slot between the two boards, the wings spread and held in place with narrow strips of paper pinned to the surface of the boards. They should remain on the board about three days to allow the wings to set. Larger bodied specimens may require a longer time to dry. The pin should be placed through the insect before it is spread. If pinned after drying the specimen will break
DISPLAY BOXES
Cigar boxes with soft, corrugated cardboard bottoms are good collecting boxes for first year projects or for storing insects.
A better display box for exhibiting insects can be made at small cost. A glass top box should be 12 x 18 × 2 1/2 to 3 1/2 inches deep. Groove the sides of the box so that the glass will slide out the narrow end of the box. Use celotex, corn board, or other soft material for the bottom so that pins can be inserted easily. Most hardware stores or lumber yards have standard window glass 12" x 18". It is easier to build the box around the standard size glass than to cut glass to fit a box.
Killing jar
After an insect is collected it should be placed in a killing jar to kill it quickly to prevent damage to the specimen.
A safe and effective killing bottle is made by placing several layers of cardboard in bottom of a glass jar, or a layer of cotton covered with a cardboard disk. Saturate the cotton or cardboard with NON FIAMABLE spot remover, or fingernail polish remover. Pour off the excess and keep the lid screwed on tightly to prevent loss of fumes.
As the bottle is used it will lose its strength so the killing fluid must be replenished from
Crustaceans
An arthropod of a large, mainly aquatic group. Includes crab, lobster, shrimp, barnacle, ...
Myriapods
An arthropod group with elongated bodies and numerous leg-bearing segments. Includes centipedes, millipedes, ...
Study outline
Vocabulary for concepts, generalizations, and outcomes:
Plants, animals, protists, arthropods, insect, arachnid, phylum, class, order, family, genus, species, metamorphosis, crustacean, amphibia, fish, diplopoda, reptile, bird, chilopoda, head, thorax, abdomen, compound eyes, wings, leg, antennae.
Classification systems organize living organism by their common properties (characteristic).
Classification of insects
Characteristics of spiders
Differences between spiders and insects.
Harmful and beneficial aspects of insects.
Activity sequence:
- Review kingdom: plant, animal and add protist
- Review plant: vascular, nonvascular, dicot, monocot, ferns, mosses, conifer, deciduous, angiosperms, gymnosperms
- Review animal classifications: mammal, fish, bird, reptile, amphibian
- Review what learners know about classification with a dichotmous key.
- Review what learners know about insects. For example may have done activities such as classification of insects & make an insect.
- Encourage learners to explore outside areas with their own insect spider explorations with starter notes.
- Review vertebrates and invertebrates.
- Introduce phylum arthropods: crustacean, insect, arachnid, diplopoda chilopoda
- What is an arthropod Smithsonian video (2.41 min)
- Discuss general characteristics of the different phylum of arthropods: crustacean, insect, arachnid, diplopoda, and chilopoda
- Make insect collections
- Discuss how to collect
- Discuss how to classify by order using the key.
- Classify insects into orders. Coleoptera, lepidoptera, hymenoptera, diptera, orthoptera, hemiptera, odonata, mallophaga, tricoptera, neuroptera, siponaptera, corrodentia, ephemeroptera, dermaptera, thysanoptera, anoplura, mecoptera, collembola, thysanura, isoptera
- Collect insects
- Classify and mount
- Repeat for two days - collect and classify
- Discuss the classification system kingdom, phylum, class, order, family, genus, species
- Read insect handout
- Discuss metamorphosis - mealworms, butterfly, grasshopper
- Monarch butterfly story (1.15 min)
- Read spider handout
- Discuss differences of spiders and insects:
- Assessment review ... 🕷
Sample focus questions, assessment questions, review ...
Name the three main parts of the insect.
Name the two main parts of the spider.
Tell four differences between spiders and insects.
Name four harmful things insects do.
Name three beneficial things insects do.
Draw and explain metamorphosis.
Name three orders, in the class insecta, and give an example for each.
Name three orders, in the class arthropoda, and give an example for each.
Name five of seven classification labels scientists use to classify living organisms.
Use the following key to identify the following organisms by writing the letter of the class that best describes each description.
This animal has a backbone, is warmblooded, lives in water, has wings, and feathers.
This animal has an exoskeleton, wings, and flies.
This animal has vertebrates, is coldblooded, swims, and has overlapping hard plates.
This animal has vertebrates, is coldblooded, lives in the desert, and has overlapping plates.
This animal has eight legs and no bones.
This animal swims, has fur, a backbone, lives in a Polar region, and maintains a constant body temperature.
Bonus question:
Tell me something you read about arthropods that wasn't talked about in class.
Cricket facts
Related to grasshoppers
Eat plants and remains of other insects
Have a long, needle like ovipositor that deposits eggs
Have wings that usually lie flat over each other on top of their backs
Can be wingless -
well known for the songs they produce mainly by the males
Sounds produced by rubbing their two front wings together
Hear sounds with organs in their front legs
Each different kind of cricket has a different song
HTML codes for spider: This is a spider f577 F577; this is the code for a smiley face ☺ ☺
Science - Investigations, activities, & teaching plans: by dimensions of science
