Insects Inside and Out

More than 100,000 species of insects are found almost everywhere in North America, but very few are harmful. Insects are important to the food chain, pollination, honey, wax, shellac, silk, food, scavenging, and decomposing.Wheel Bug

Lady beetle adult and larva -good or bad?Let's examine which insects are "good" and which ones are "bad". Are lady beetles good or bad? Well, they are good when they eat aphids, but bad when hundreds collect inside your house.

Jim Kalish Dept. of Entomology, University of Nebraska-LincolnHoney bees - good or bad?Are honey bees good or bad? They are good whenthey pollinate and produce honey, but bad when they sting.

Termites - good or bad?They are bad when they eat the wood in your house, but good when they break down dead and fallen trees. 1998-2003 Troy Bartlett

KingdomPhylumClass OrderFamilyGenusspeciesIn school we learned that animals are divided intosmaller and smaller groups. Let's look where insects fit in the animal kingdom. From top to bottom, each category has fewer species, and the groups of animals within each category are increasingly similar.

Kingdom- animalPhylum - arthropodClass - insectOrder - dipteraFamily - muscidaeGenus - Muscaspecies - domesticaUsing the house fly as an example. Notice the genus and species is the official scientific name of the animal. This name is valid in any country of the world and is an important way to avoid confusion. This two-word Latin naming system was developed in 1758 and has hardly changed since then. There are some important things to know about it.

House FlyMusca = flydomestica = homeScientific names are always two words. The first part of the name (Genus) is always capitalized. This lets us know that it is the genus. The second name is always in lower case and is usually descriptive of the insect in some manner. Because these words are in Latin, they are always italicized (or underlined which substitutes for italics).

Interesting Scientific NamesEubetia bigaulae Brown (tortricid moth)

Interesting Scientific NamesEubetia bigaulae Brown (tortricid moth)

Heerz lukenatcha Marsh (braconid wasp)

Interesting Scientific NamesEubetia bigaulae Brown (tortricid moth)

Heerz lukenatcha Marsh (braconid wasp)

Pieza rhea Evenhuis (mythicomyiid fly)

Interesting Scientific NamesEubetia bigaulae Brown (tortricid moth)

Heerz lukenatcha Marsh (braconid wasp)

Pieza rhea Evenhuis (mythicomyiid fly)

Verae peculya Marsh (braconid wasp)

Insects also have common names. One problem with common names is that there may be more than one common name for the same insect. Common names often differ between geographical regions. Do you know what a skeeter hawk is? Or a cow killer? Did you know a velvet ant really is not an ant, but a wingless wasp? ...and locusts are really a type of grasshopper - not a cicada.

Skeeter HawkCow KillerVelvet antCicadaLocustLocust

honeybeebumble beehoney beeImportant rules govern the use of common names. If the insect truly belongs to the group that the name denotes, then the common name should be two words. For example, a honey bee is a true member of the bees, so honey bee (or bumble bee) is always spelled as two words despite what your common dictionary may print.

Which of the following should be two words?butterflydragonflyhorseflyhouseflywhiteflydamselflyfruitflymayfly

Only these insects are true fliesbutterflydragonflyhorse flyhouse flywhiteflydamselflyfruit flymayfly

External AnatomyheadabdomenthoraxAdult insects are known for having three major body regions, six legs, one pair of antennae and usually two pair of wings as adults.

from the 1995 Physiology or Medicine Nobel PosterAdult insects develop as a composite of fused segmentswith specific body part associations.

headmouthpartsantennaecompound eyesHEADThe first body region is the head. Insect heads can behighly variable, but most possess eyes, antennae and mouthparts.

AntennaeJune beetletermiteflybutterflyantbeetleAntennae are used by insects as major sensory devices, especially for smell, and can be adaptive for the insect in many ways.

Two Examples of Mouthpartschewingpiercing/suckingInsect mouthparts are also highly modified for theinsect. Chewing, biting, or sucking, are a few examples. Mouthparts of an immature insect may differ from those of the same insect in its adult stage.

Picture of bodypartsThoraxThe middle body region is called the thorax and is composed of three fused segments. All legs and wings are located on the thorax.

LegssuctiondiggingswimminggraspingLike the mouthparts and antennae, insect legs are quitevariable in form and function and reflect the insect's lifestyle.

AbdomenThe last body region is called the abdomen. It is composed of many segments connected by flexible sections allowing it great movement.

Insects possess an exterior covering called the exoskeleton. They do not have internal bones. This segmented "shell" is what gives insects shape and can be very hard in some insects. It is often covered with a waxy layer and may have "hairs" called setae.

Exoskeleton x-sec waxy layerseta ( hair)cuticle

InternalAnatomyInside the insect we find the systems for respiration, circulation, nerves, and digestion, but there is little resemblance to the same systems found in man or other mammals.

Digestive sysDigestive SystemforegutmidguthindgutThe digestive system is a tube that opens at the mouth and empties at the tail end of the insect. It is divided into three parts called the foregut, midgut, and hind gut. In some insects such as the honey bee, the foregut acts as a crop to carry or hold liquids which can be regurgitated later.

Circ systemCirculatory Systemaortic pumps heart The circulatory system is not composed of a central heart, veins and arteries which circulate blood cells and transport oxygen. The insect circulatory system is a simple tube down the back which is open at both ends and slowly pulses body fluids and nutrients from the rear of the insect to the head.

Nervous systemNervous Systemnerve bundlestwo lobed brain(ganglia)Insects have a less centralized nervous system than humans. The nerve chord runs along the ventral or bottom aspect of an insect. The brain is divided into two main parts. The largest lobes control important areas such as the eyes, antennae, and mouthparts. Other major concentrations of nerve bundles called ganglia occur along the nerve chord and usually control those body functions closest to it.

The respiratory system is composed of air sacs and tubes called tracheae. Air enters the tubes through a series of openings called spiracles found along the sides of the body. The largest spiracles are usually found on the thorax where greater musculature from wings and legs require more oxygen. There are no spiracles on the head.

spiraclestrachealtubesRespiratorySystem

LifeCyclesThe many diverse orders of insects have four different types of life cycles. These life cycles are called "metamorphosis" because of the changes of shape that the insects undergo during development.

Without metaWithout MetamorphosiseggadultnymphsThe first type is "without" metamorphosis which the wingless primitive orders such as silverfish (Thysanura) and springtails (Collembola) possess. The young resemble adults except for size.

Incomplete metaIncomplete MetamorphosiseggnaiadsadultThe second type is "incomplete" metamorphosiswhich is found among the aquatic insect orders such as mayflies (Ephemeroptera) and dragonflies (Odonata).

Gradual metaGradual MetamorphosiseggnymphsadultThe third type is "gradual" metamorphosis seen in such orders as the grasshoppers (Orthoptera), termites (Isoptera), thrips (Thysanoptera), and true bugs (Hemiptera). This life cycle starts as an egg, but each growth, or nymphal stage looks similar, except it lacks wings and the reproductive capacity that the adult possesses.

Complete MetamorphosisegglarvaepupaadultThe fourth type is "complete" metamorphosis found in butterflies (Lepidoptera), beetles (Coleoptera), flies (Diptera), and bees, wasps, and ants (Hymenoptera). This life cycle has the four stages of egg, larva, pupa, and adult. Each stage is quite distinct.

recently molted roachIt should be noted that because insects are hard-bodied, they cannot grow larger gradually. Instead they grow larger in steps by shedding the hard exoskeleton for a brief period of expansion. The brief periods between or within stages are called molts. Insects are soft-bodied and vulnerable during this time.

Jack Kelly ClarkToday we've discussed what makes an animal an insect and the main characteristics of an insect. Hopefully you will have a better understanding of how insects fit into our environment and why they do some of the things they do.

Stephen B. BambaraExtension EntomologistNC STATE UNIVERSITYPrepared byCopyright 2001