Matt Bertone

Entomology is the study of insects (Arthropoda: Hexapoda) and related organisms. Insects make up most of the diversity of life on Earth; they and their close relatives, crustaceans, arachnids, and myriapods, have been the dominant macroorganisms on the land and in the oceans for millions of years. There are approximately 925,000 known species of insects (1.5 million species of arthropods), or more than half (with other arthropods 75%) of all known organisms. Each of these species occupies a particular niche on Earth, and the ways in which they have invaded the landscape are countless.

One of the great things about studying insects is they do almost everything and can be used in many different fields of science - from studies on sociality and ecology, to biomimetics (engineering using designs found in nature) and genetics (for example Drosophila melanogaster). Insects are probably most known for their interactions with humans. When you stop and think, how many animals do you regularly come in contact with? Most of the crawling or flying things we see are insects or their relatives. Insects also affect us directly or indirectly, either by causing harm or benefiting us. Insect pests account for about 30% of plant crop losses every year, and that's with pesticides and other control measures. They also invade (and eat) our homes and food, drink our blood and can give us diseases, and become annoyances when in large numbers. In fact, insects and their relatives have been so important throughout human history that 3 of the biblical plagues were insects (fleas/flies, locusts,and lice)! Insects eat almost anything organic (and sometimes things that aren't!) including plants, other animals, fungus, microorganisms and rotting materials. They also live in most habitats, and exist on all continents including Antarctica. Insects do just about everything any other animals can do (just on a smaller scale).

I study the diversity and evolution of insects (from here on referring to all Hexapoda). This includes the history of insects since their emergence on the earth 420-460 million years ago. Insects were the first flying animals on earth and have been in the air for about 380 million years, though they had also been dominating the land and fresh water with their arthropod relatives (such as scorpions, spiders, millipedes and others). Some groups have not changed much since that time, including dragonflies and mayflies. Other lineages were still primitive compared to todays members, but would have been recognized as strange insects. Some insects even grew to impressive sizes: extinct dragonfly relatives and other insects had two foot wingspans! Insects continued to evolve and diversify over millions of years, until 20-50 million years ago when many of the insects would have been generally recognized by people today. However, insects (as with all organisms) continue to adapt to the ever changing planet and millions of years from now they may evolve into very different, unrecognizable forms.

Modern insects are divided into about 32 orders* (depending on the classification), which are considered the major groups. The most "primitive" of these are the entognaths ("inside-jaws"), including springtails (Collembola), proturans (Protura) and diplurans (Diplura). They are generally minute, soft-bodied soil organisms, though springtails are very common and can even become pests of crops. The next group of insects, jumping bristletails (Microcoryphia) and silverfish (Zygentoma), includes what we often refer to as "primitively wingless" insects and are the most ancestral of the true-insect hexapods. These insects are found in nature but also frequent human dwellings, especially silverfish and firebrats. They often feed on starchy substances and have many physical characteristics reminiscent of their ancient origins - styli on the underside of their abdomen are remnants of ancient appendages and they keep molting (shedding their skin) throughout their lives, unlike other insects.

Dragonflies/damselflies (Odonata), and mayflies (Ephemerida) are what we often refer to as the paleopteran ("ancient-winged") insects, so-called because they are unable to fold their wings flat over their body. They are almost always associated with water, where their young live. Dragonflies and damselflies are all predators as immatures and adults. Adults are strong fliers - they can maneuver in the air excellently and are known to migrate long distances. The order name for mayflies - Ephemerida - alludes to that fact that most adult mayflies do not live more than a day or two. However, their young have many different habits and can live for many years. Mayflies are unusual in that they are the only winged insects that molt after they get their wings.

The polyneopteran insect orders comprise a large and variable group of ancient insects, ones that were the first to develop the ability to fold their wings. They are united mainly by the enlarged posterior area of the hind wing. Many of these orders are familiar to us, while others are geographically limited and, thus, more obscure. Stoneflies (Plecoptera) represent a relatively large group of ancient looking insects. They are associated with water, where their young live and feed on algae, detritus and, less often, other small animals. Adults have two conspicuous cerci on the tip of their abdomen and are often elongate and cigar-shaped. Webspinners (Embiodea) are an interesting group of secretive insects that are rarely encountered and are most diverse in the tropics and semi-tropics. The order gets its common name from the fact that members have enlarge forelegs (more specifically fore-basitarsi) that produce silk. They use the silk to create tubes/galleries that lie on surfaces including trees, leaf litter and human structures. Female webspinners are wingless, while males have wings that can be made flexible to allow movement in many directions within their tubes. Zorapterans (Zoraptera, sometimes called "angel insects") are represented by only 32 species worldwide, and all are small insects (< 3mm). They were initially thought to be entirely wingless (Zoraptera meaning "wholly-wingless"), but we now know that, at least in some species, there are two forms: a lightly colored, eyeless and wingless form, and a darker, eyed and winged form. They are usually found in groups under bark or logs where they feed on fungus and minute animals. Earwigs (Dermaptera) are, to many people, synonymous with human brain infestations, but that is very far from the truth. Earwigs are cryptic omnivores that are mostly recognized for their enlarged, pincer-like cerci at the end of their abdomen. Though they look scary, they use these forceps to fold their wings under their short wing covers, hunt prey and defend themselves. Earwigs mothers are known to protect their young during their early development, while some earwig species live in close association with giant rats and bats. Rock crawlers (Grylloblattodea) are a geographically-limited order, with 26 known species found only in the northern hemisphere. They are all wingless and well adapted to life in frigid environments. In fact, they can only be collected in cold, icy, montane habitats where they are most active in temperatures just above freezing. They are considered omnivores, taking dead organisms killed by the cold and vegetable matter. Heelwalkers (Mantophasmatodea) are members of the newest order, only just described in 2002. They are only found in southern Africa, but have a larger fossil distribution. They are all wingless and built for being predators: they have large raptorial front legs and large eyes. Some recent taxonomists consider rock crawlers and heelwalkers as one order, Notoptera.

More to come...

*As with the number of orders, which can change with new evidence, not all authors agree on the names for some orders. Here I am using the names I would currently attribute to these groups based on recent literature.

Entomologists use many different tools to capture, preserve and study insects. Below is a poster illustrating many of the instruments used in insect research (click to enlarge):

REFERENCES:
Evolution of the Insects, Grimaldi & Engel. Cambridge University Press.
The Timetree of Life.
Insects: Their Natural History and Diversity, Stephen Marshall. Firefly Books