Pests, predators, and pollinators, whatever role they play in the garden, insects are everywhere. Or, are they?
Most of the world’s insects evolved in tandem with flowering plants (angiosperms). The majority of insects are small, but a few of those early insects were huge by today’s standards. Dragonflies, known as predatory griffinflies, had wingspans of over 2 feet, and cockroaches were the size of house cats. This was due, in part, to higher oxygen levels in the atmosphere. [31-35% oxygen then, 21% today - don’t panic, though, these levels have been fluctuating since Earth was formed.
Changing oxygen levels were not the only reason for some insects getting smaller. Research has demonstrated that the evolution of insect-eating birds, around 50 million years ago, also played a big role in this change. As bird (and bat) predators started feeding on insects, those prey animals had to become more mobile, harder to see, and less delicious to survive.
Today, insects are facing the biggest threat to their existence - us.
Recent studies show an alarming decrease in insect populations around the globe. Today, we will be learning about different types of insects, the benefits they provide, the problems they face, and ways we can help.
Insects are spineless, 6-legged, armor-plated creatures with three-part bodies, compound eyes, and antennae. To put those characteristics in more scientific terms, insects are invertebrate hexapods with a chitinous exoskeleton.
The word ‘insect’ comes to us from the Latin word insectum, which means ‘with a divided body’. An insect’s body consists of the head, thorax, and abdomen. The legs and wings attach to the thorax. Insects have two types of eyes: simple and compound. Simple eyes (ocelli) are a single lens that can see clearly. Most insects have three simple eyes on top of their head. Compound eyes are those bulging eyes we can easily see. Insects’ compound eyes can have dozens, hundreds, or even thousands of lenses, called facets.
Insects represent between 50 and 90% of all living things on Earth, with over one million named species, and an estimated 4 to 10 million unnamed species. Cousin to spiders and crustaceans, insects come in an astounding array of shapes, sizes, and colors.
A bug by any other name
All bugs are insects, but not all insects are bugs. The word ‘bug’ only refers to true bugs (Hemiptera). True bugs all share piercing, sucking mouthparts that may be used on plants or other insects. There are approximately 80,000 different types of true bugs worldwide, along with 12,000 ant species, 20,000 bee species, and 400,000 types of beetles.
Insects are first classified as winged (Pterygota) or wingless (Apterygota), though not all winged insects can fly. Winged insects are further classified by when and where those wings develop. True flies, bees, fleas, ants, beetles, and butterflies and moths go through a complete metamorphosis, with the wings developing inside the insect during a pupal stage. These insects are in the Endopterygota order. Insects whose wings develop outside of the body, as with dragonflies, lice, mantids, and earwigs, it is considered an incomplete metamorphosis and these insects are in the Exopterygota order.
Most insects hatch from eggs. Rigid exoskeletons are shed in a series of molts, as an insect grows. Some baby insects, such as praying mantis, look like miniature adults, while other insects, such as the Monarch butterfly, go through a complete, 4-stage metamorphosis that includes a pupal stage. While other insects have a 3-stage metamorphosis, in which there is no pupal stage, but a series of nymphal stages.
Pests, parasites and pollinators
Insects are profoundly important components of an environment. They aerate the soil, eat pests, pollinate one-third of all crops (by volume), feed local wildlife (and domestic chickens!), and recycle natural materials into forms usable by plants. Insects play a major role in the creation off topsoil. Insects are also eaten as food by 80% of the world’s nations. Insects can also carry disease, destroy crops, and damage buildings.
Initially, chemical insecticides were seen as the first line of defense against unwanted insects. Because many insects are able to develop a tolerance to those dangerous chemicals (and we cannot), other methods of control are being explored. Very often, beneficial insects, such as parasitic wasps, and other natural predators, such as birds, are encouraged or imported into an area to control harmful insects. These integrated pest management methods reduce our reliance on chemicals and increase local biodiversity.
Declining insect populations
We have been so focused on killing insects off that we didn’t notice, at first, when their populations started to decline, or by how much. Hard, verifiable population facts are still difficult to come by, but recent research has shown a 45% decline in invertebrate populations worldwide. Now, that figure includes more than just insects, but the news is alarming. One German entomological society has recorded nearly 80% less insect biomass in their studies. Another German study reported a 75% decrease in the total flying insect biomass over a 27 year study on 63 different sites. Now, biomass does not mean number of insects. It also does not tell us which type of insects. It simply tells us the amount of insects by weight. Also, not all sites were studied every year, so please do not take this study to say that ’75% of all insects disappeared over 27 years’, because that’s not what the study claims. What it does tell us is that this is a very real problem.
Declining insect populations are the result of many different factors:
The food web ties all living things together. As insect populations fall, so do bird, bat, fish, and amphibian populations. European ornithologists (bird experts) point to declining insect populations as a fundamental reason behind 80% less partridges and turtledove, and 50% less nightingales currently found in the French countryside. In the past 30 years, over half of all Europe’s farmland birds have disappeared, and we have to assume that similar results are occurring locally.
Call to arms
Scientists recognize the critical nature of insect population decline, and the lack of verifiable information. To counteract that lack, large-scale monitoring is being called for, using photos, videos, acoustic recordings, traps, genetic fingerprinting, and citizen science. Automated data collection, worldwide, is the only way we can learn where insects are and how their populations are behaving, and you can help, too.
How you can help insects
There are many things you can do to help insects at home:
Did you know that earwig mothers clean, protect, and keep their eggs warm?
Now you know.
You can grow a surprising amount of food in your own yard. Ask me how!