When it comes to insects, Mother Nature has shown here’s almost no limit to how a simple concept can vary. Perhaps one of the best ways to see this is in insect wings. These wings have an incredible amount of variation, extending right down to the microscopic level.
But before we can get into the different types, we need to first go over a few important definitions, as it can be next to impossible to understand the differences in wings if you don’t have any grasp of all the scientific jargon.
- Axillary Area – Simply put, this is where the wing is attached to the thorax.
- Clavus – This is the vanal area of the forewing.
- Coastal Margin – This is the leading edge of the wing
- Forewing and Hindwing – When an insect has two pairs of wings instead of one, the front pair are the forewings and the back pair are the hindwings.
- Frenulum – Found on many Lepidoptera, the frenulum is a large bristle found on the hindwings that holds the hindwings and forewings together while in flight.
- Hamuli – These are a series of tiny hooks on the coastal margin of hindwings in many insects, such as bees and wasps. When the insect takes flight, the hooks connect the hindwings to the forewings, allowing them to function as a single surface.
- Jugal Area and Jugum – The Jugum is a portion of the vannal area on the inside edge of the wing that doesn’t connect to the thorax. Sometimes referred to as the jugal area, this portion is separated from the rest of the vannal area by the jugal fold.
- Longitudinal and Cross Veins – Longitudinal veins run the length of the wing and can be convex or concave in shape. Meanwhile, cross veins connect the longitudinal veins.
- Pterostigma – Also referred to as the stigma, this is a small pigmented spot near the coastal margin.
- Vannal Area – The back of the wing where there are very few veins is the vannal area, sometimes called the anal area.
- Vannus – This is the vannal area on a hindwing.
- Veins – These hollow tunes resemble actual veins but don’t carry blood. Instead, they exist to provide more strength to the wings without adding excess weight.
- Wing Venation – This is the pattern of veins on the wing.
Of course, this still barely scratches the surface, but now that you have a basic understanding of these important terms, it will be easier to understand the different types of insect wings out there.
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Types of Insect Wings
Found primarily in beetles, an elytron is a hardened, shell-like forewing that’s sometimes referred to as a shard. They serve as a protective cover for the membranous hind wings and generally have no venetians themselves.
When a beetle is about to fly, it will open the elytra, then expand its hindwings. In most cases, the elytra will remain open in flight, although some members within the families of Buprestidae and Scarabaeidae have the ability to fly with the elytra closed.
Some beetle families, such as Ripiphoridae are Staphylinidae, the elytra are reduced and may be no longer functional. Meanwhile, the opposite is true of many ground beetles, such as scarab beetles and weevils.
In these beetles, the hindwings are absent while the elytra have become fused into a single protective shell and are otherwise no longer functional.
2. Fissured Wings
Fissured wings can be found on the plume moth and a few other species of insect and are quite distinctive in their appearance. The forewing has a longitudinal cut from the tip partway down, giving the wing a forked appearance.
The hindwing is similarly divided, but has two such fissures, resulting in three tips. Small marginal hairs line the forks. This peculiar adaptation thus includes the benefits of both scaled and fringed wings in a single design.
3. Fringed Wings
Found on small insects such as thrips, fringed wings are quite curious when seen under a microscope. The wings themselves are long and somewhat narrow with less venation.
Along the coastal and vannal areas are long marginal hairs that expand the overall surface of the wings. The fringes give these wings a very feather-like appearance and aid such tiny insects in flight using sheer force to beat the air.
As life evolves, some changes can be quite drastic while others can be clearly visible. For example, some species of snakes have vestigial limbs, proving that at one point at least some snakes had legs. There are also some species of insects which seem to evolve and devolve wings in cycles.
Halteres (or halter for a single wing) are a perfect example of this evolutionary process. Halteres are tiny, club-shaped organs found on the orders of Diptera and Strepsiptera.
These curious limbs are actually devolved wings, with the halteres of Strepsiptera being the result of devolved forewings while on Diptera they’re the remains of the hindwings. However, while these strange organs may have come from different parts of the two orders, the function is the same.
When the insect is in flight, the halteres beat just like their normal wings. At the base of the halteres are tiny sensory organs that can be found at the base of most hindwings. Known as campaniform sensilla, these organs can detect the positioning of the halteres and function much like organic gyroscopes.
On a level, straight flight, the halteres beat up and down, but as the insect’s orientation changes along the three axes (pitch, yaw, and roll), the halteres begin to move left and right in addition to up and down. This causes staring to tiny bell-shaped structures at the base of the halter.
This stress is transmitted via electrical signals through the nervous system to the insect’s brain, allowing it to correct its position in flight and maintain a stable flight path.
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Found in some true bugs, including the family Schizopteridae, hemelytra (AKA hemielytra) are membranous forewings which have a thickened base resembling an elytra.
In a few cases, the wing has become completely thickened. This condition is known as being coleopteroid.
6. Membranous Wings
When you think of insect wings, this is probably what you’re picturing. These wings are transparent with numerous lateral veins connected by cross veins. In some cases, the wings will reflect light like a prism at the right angle, although this is not always true.
Most flying insects have a pair of membranous wings, including beetles (hind wings with elytra), dragonflies (both hind and forewings), grasshoppers and crickets (hindwings with tegmina forewings), or on insects with a single pair or hamuli-equipped wings wings, such as bees and wasps.
Unlike many other types of insect wings, membranous wings are always used for flight.
This term can be a little confusing. In the most basic definition, these are modified halteres that are shorter and more dumbbell-shaped. However, some sources use the term to distinguish between the halteres of Diptera (AKA flies) and those of Strepsiptera.
According to this description, pseudohalteres aren’t defined by size or shape. Instead, they’re defined by their position on the insect’s body.
Proponents of this definition point to the fact that the halteres on all dipteras are devolved hindwings and can be found in the same place on all species. However, on a strepsiptera, these are the devolved forewings and are located between the first and second legs. Thus, they consider them to be a similar, yet different organ from diptera halteres.
Of course, this is a matter for academic debate, and neither definition has gained universal acceptance in scientific circles, so either definition of the term may be considered as acceptable.
8. Scaly Wings
These are thin, membranous wings that aren’t transparent. Instead, they’re covered in tiny, unicellular colored scales. Both moths and butterflies have scaly wings.
The scales themselves overlap and completely cover the wing surface. Not only do these provide the coloration butterflies are well-known for, they also aid in flight by smoothing the airflow across the wings.
These forewings, singularly called tegmen, are tough and leathery. You can find them on insects belonging to several orders, such as: Blattodea (cockroaches), Dermaptera (earwigs), Mantodea (praying mantis), Orthoptera (grasshoppers, crickets and similar families), and Phasmatodea (stick and leaf insects).
The specific role of tegmina can vary a bit, but the general consensus is that they evolved to protest the more fragile hindwings when they’re folded. They’re often dully colored to hide more brightly colored wings, allowing the insect to startle potential predators.
In other species, such as some mantids, large markings are hidden when folded but resemble large eyes when opened as another means to intimidate potential predators.
However, in other species, these wings serve very different functions. For example, Orthoptera use their tegmina for soundboards.
Many species of crickets have highly modified tegmina to aid in sound production, while some locust species use their tegmina to produce loud cracking sounds. While aerodynamic in nature, they don’t provide any significant role in flight itself.