10 Fascinating Facts About Insects

Insects May Be Small, but They Use It to Their Advantage

While being a tiny bug in a big world is certainly a challenge, there are some useful advantages to being small. An insect doesn't have much body mass, but the surface area of its body is large in proportion to that mass. And that means physical forces don't affect insects the way they do larger animals.

Because the ratio of their body mass to surface area is so large, they can accomplish physical feats impossible to humans, or even to small animals like birds or mice. An insect can withstand falls because its minimal weight means it lands with significantly less force. An insect's relatively large surface area creates a lot of drag as it moves through the air, so it slows down as it reaches the end of its travels. Insects like water striders can literally walk on water, by distributing their low body mass in a way that maximizes the water's surface tension. Flies can walk upside down on ceilings without falling, thanks to modified legs and light bodies. 

They Outnumber All Other Terrestrial Animals Combined

As a group, insects dominate the planet. If we count every kind of land animal known thus far, from rodents to humans and everything in between, that total is still only about a third of the known insect species. We've only begun to identify and describe the insects on earth, and the list is already over one million species and climbing. Some scientists estimate the actual number of distinct insect species may be as high as 30 million. Unfortunately, a good number will likely be extinct before we even find them.

While the greatest abundance and diversity of insects occur in the tropics, you can find a remarkable number of insect species in your own backyard. The authors of Borror and Delong's Introduction to the Study of Insects note that "more than a thousand kinds may occur in a fair-sized backyard, and their populations often number many millions per acre." Several insect enthusiasts have launched backyard bug surveys in recent years, and have documented hundreds, sometimes thousands, of unique species in their own yards.

Their Colors Serve a Purpose

Some insects are dull and drab, colored only in flat black or brown from antennae to the abdomen. Others are resplendent and sparkly, in patterns of fiery orange, royal blue, or emerald green. But whether an insect seems boring or brilliant, its colors and patterns fulfill an important function vital to that insect's survival.

An insect's color can help it avoid enemies and find mates. Certain colors and patterns, called aposematic coloration, warn potential predators that they're about to make a bad choice if they try to eat the insect in question. Many insects use color to camouflage themselves, effectively allowing the insect to blend into its environment. Their colors can even help insects capture sunlight to help it stay warm, or reflect sunlight to keep it cool.

Some Insects Aren't Really Insects

The classification of arthropods is fluid, as entomologists and taxonomists gather new information and reassess how organisms relate to each other. In recent years, scientists determined that some six-legged arthropods that were long considered insects really weren't insects at all. Three arthropod orders that were once neatly listed under the Class Insecta were cast aside.

The three orders – Protura, Collembola, and Diplura – now stand separately as entognathous hexapods instead of insects. These arthropods do have six legs, but other morphological traits distinguish them from their insect cousins. The most important trait they share is mouthparts that are retracted and concealed within the head (which is what the term entognathous means). The Collembola, or springtails, are the most familiar of these three not-really-insects insect groups. 

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By Debbie Hadley

They First Appeared on Earth at Least 400 Million Years Ago

The fossil record of insects takes us back an astounding 400 million years. The Devonian period, though called the Age of Fishes, also saw the growth of terrestrial forests on dry land, and with these plants came insects. While fossil evidence of insects from before the Devonian period is unlikely to exist, we do have fossil plant evidence from that time. And some of those fossilized plants show evidence of being munched on by mites or insects of some kind.

In the Carboniferous period, insects really took hold and started to diversify. Ancestors of modern day true bugs, cockroaches, dragonflies, and mayflies were among those crawling and flying among the ferns. And these insects weren't tiny, either. In fact, the largest known of these ancient insects, a dragonfly predecessor called a griffenfly, boasted a wingspan of 28 inches.

They All Have the Same Basic Mouthparts, but Use Them Differently

Insects from ants to zorapterans share the same basic structures to form their mouthparts. The labrum and labium essentially function as the upper and lower lips, respectively. The hypopharynx is a tongue-like structure that projects forward. The mandibles are the jaws. And finally, the maxillae may serve several functions, including tasting, chewing, and holding the food.

How these structures are modified reveals a lot about how and what an insect eats. The type of mouthparts an insect has can help you identify its taxonomic order. True bugs, which include many sap-feeding insects, have mouthparts modified for piercing and sucking fluids. Insects that feed on blood, like mosquitoes, also have piercing, sucking mouthparts. Butterflies and moths drink fluids and have mouthparts formed into a proboscis or straw for doing so efficiently. Beetles have chewing mouthparts, as do grasshoppers, termites, and stick insects.

There Are Three Different Kinds of Insect "Eyes"

Many of the adult insects we observe have large eyes called compound eyes for detecting light and images. Some immature insects have compound eyes, too. Compound eyes are made up of individual light sensors known as ommatidia, lenses that work together to enable the insect to see what's around it. Some insects may have just a few ommatidia in each eye, while others have dozens. The dragonfly eye is perhaps the most sophisticated of all, with more than 10,000 ommatidia in each compound eye.

Most insects have three simple light detection structures called ocelli on the top of their heads, in both the adult and immature stages of their lives. The ocelli don't provide the insect with sophisticated images of its environment, but simply help it detect changes in light.

The third kind of eye is barely an eye at all. Some immature insects – caterpillars and beetle larvae, for example – have stemmata on the sides of their heads. The stemmata detect light on either side of the insect and probably help the immature insect navigate as it moves.

Some Insects Fill Specific Ecological Roles

Over 400 million years of evolutionary time, some insects have evolved to perform remarkably specialized roles in their ecosystems. In some cases, the ecological service an insect provides is so specific the insect's extinction might unravel the balance of that ecosystem.

Nearly all caterpillars are phytophagous, but one unusual moth caterpillar (Ceratophaga vicinella) scavenges on the tough keratin shells of dead gopher tortoises. There are numerous examples of flowering plants that require a specific insect pollinator to set seed. The red disa orchid, Disa uniflora, relies on a single species of butterfly (the mountain pride butterfly, Aeropetes tulbaghia) for its pollination. 

Some Form Relationships, and Even Care for Their Young

Insects may seem like simple beings, incapable of establishing bonds of any kind with other individuals. But in truth, there are numerous examples of insects that parent their young to some degree, and a few cases of insects that do so together in male-female couples. Who knew there are Mr. Moms among the arthropods?

The simplest such care involves a mother insect guarding her offspring as they develop. This is the case with some lace bug and stink bug mothers; they guard their eggs until they hatch, and even stay with the young nymphs, fending off predators. Giant water bug fathers carry their eggs on their backs, keeping them oxygenated and hydrated. Perhaps the most remarkable example of insect relationships is that of the bess beetles. Bess beetles form family units, with both parents working together to rear their young. Their relationship is so sophisticated they've developed their own vocabulary and communicate with each other by squeaking.

They Rule the World

Insects inhabit virtually every corner of the globe (not that globes have corners). They live on glaciers, in tropical jungles, in scorching deserts, and even on the surface of the oceans. Insects have adapted to living in the darkness of caverns and at altitudes only a Sherpa can appreciate.

Insects are the planet's most efficient decomposers, breaking down everything from carcasses to dung to fallen logs. They control weeds, kill crop pests, and pollinate crops and other flowering plants. Insects carry viruses, bacteria, and protozoa (for better or worse). They farm fungus and disperse seeds. They even help control populations of large animals by infecting them with diseases and sucking their blood.