This video goes over insects that are hemimetabolous and develop wings on the outside of their body, including walking sticks, mantids, true bugs, thrips, and …
Hi, this is Dr. DeBusk. Now we are moving into Neopteran phylogeny
which means “new wing”. Neopterans include
most orders of the winged insects, specifically
those that can flex their wings over their
abdomens.
In Division Exopterygota, we have a large
group of insect that still have hemimetabolous
or incomplete development, but these are not
going to have an aquatic larval stage. The
young resemble adults but have externally
developing wings. They undergo only a modest
change between immature and adult, without
going through a pupal stage. The nymphs develop
gradually into adults through the process
of molting. In your collection, the majority
of the insects must be adults. If they have
wing pads and not fully developed wings, then
it is an indication that they are still nymphs.
Earwigs make up the order Dermaptera. They
have a slender flattened body, bead-like antennae,
and are easily recognized by the pair of large
pincers or cerci at the tip of the abdomen.
Some are wingless, but in most, the forewings
are represented by short leathery covers called
tegmina, under which the membranous hind wings
(if present) fold in a unique fan-like fashion.
Hence the name “skin wings”. Earwigs are
mostly nocturnal and often hide in small,
moist crevices during the day and are active
at night, feeding on a wide variety of insects
and plants with their chewing mouthparts.
Many earwig species display maternal care,
which is uncommon among insects. Female earwigs
may care for their eggs, and even after they
have hatched as nymphs will continue to watch
over offspring until their second molt. The
name “earwig” is more popularly thought
to be related to the old wives’ tale that
earwigs burrowed into the brains of humans
through the ear and laid their eggs there.
Earwigs are not known to purposefully climb
into ear canals, but there have been anecdotal
reports of earwigs being found in the ear.
You can tell that you have now entered the
section of neopterous insects. As you can
see, the wings are folded on top of each other
over the abdomen and are not held out to the
side or straight back. The forewings are narrower
than the hind wings, hardened or leathery
at the base, held roof-like overlapping the
abdomen at rest. The hind wing is membranous
and held folded fan-like under the forewings
when at rest. Orthoptera comprises the grasshoppers,
locusts, and crickets, as well as katydids
and wetas. They have large compound eyes,
hind legs adapted for jumping, and long or
short antennae. They also have a tympanum
or ear located in the front tibia or first
abdominal segment, using vibrations to locate
other individuals. Their use of sound is generally
crucial in courtship, and most species have
distinct songs.
Insects in order Phasmatodea include stick
insects or walking sticks. Most are elongate
and cylindrical or flattened and resemble
sticks, leaves, or grass. They are herbivorous
with chewing mouthparts. They have 2 pairs
of wings although some species are wingless.
Wings when present consist of short, hardened
forewings which form a protective cover over
part of the larger membranous hind wings.
Their antennae are filiform, either short
or long. Many phasmids are parthenogenic and
do not require fertilized eggs for female
offspring to be produced. Eggs are dropped
to the ground from the trees. Phasmid nymphs
usually resemble adults but lack wings. Besides
being able to camouflage into the plants,
they also have defensive secretions from their
thorax. They can also regenerate their legs
and consist of some of the longest insects
in the world.
Mantids in the Order Mantodea have triangular
heads with bulging eyes supported on flexible
necks. Their elongated bodies may or may not
have wings, but all Mantodea have raptorial
forelegs that are greatly enlarged and adapted
for catching and gripping prey; their upright
posture, while remaining stationary with forearms
folded, has led to the common name praying
mantis. The eggs are protected by their hard
capsules and hatch in the spring. Females
sometimes practice sexual cannibalism, eating
their mates after copulation. Nymphs look
like small adults but lack wings or have developing
wing buds.
Blattodea contains cockroaches and termites.
Formerly, the termites were considered a separate
order, Isoptera, but genetic and molecular
evidence suggest that they evolved from a
common ancestor. They share a dorso-ventrally
flattened body with filiform antennae, cursorial
or running legs, and chewing mouthparts. Both
termites and cockroaches engage in coprophagy,
the consumption of fecal pellets. They are
also attracted to warm and humid places, have
thigmotaxis (they like tight spaces), groom
themselves, communicate among species, and
many other behaviors. Cockroaches are considered
pre-social since they tend to aggregate. Cockroaches
have a shield-like plate, the pronotum, that
covers its thorax and posterior region of
the head. The forewings are normally leathery
while the hind wings are membranous. Female
cockroaches produce an egg sac known as an
ootheca and can hold anywhere from 12-25 eggs
depending upon the species.
Termites are also known as white ants. They
are the only hemimetabolous insect with true
social behavior. These insects have a caste
system that includes workers, soldiers, and
reproductives. The worker is the bread winner
of the family. They are nearly blind and they
forage for food by building tunnels to protect
themselves. The workers are charged with soldier
termites protecting the colony. They have
a larger head than the common workers and
large strong mandibles. Termite colonies consist
of both males and females and the king remains
with the queen in the colony. Although ants
and termites may look similar to the untrained
eye, termites differ in that they have a wider
waist, beaded antennae compared to elbowed,
and equal-sized wings.
Thrips are in the Order Thysanoptera. Some
thrips are common pests of plants. They are
very small, slender insects with unique mouthparts.
They inject their cone-like rasping-sucking
mouthparts into the plant and suck the juices
of the buds, flowers or fruits of the plant
causing damage to these structures. Some species
are predaceous and feed on mites and other
thrips. Adults can be winged or wingless.
The wings are thin and are covered with a
fringe of hairs. Thrips are hemimetabolous,
but they may have a pseudo fringe wing pupal
stage with a silken cocoon. This puzzles scientists
and may be an instance of convergent evolution.
The Hemiptera or true bugs comprise of 50,000
to 80,000 species and include cicadas, aphids,
planthoppers, leafhoppers, and shield bugs.
They all have piercing-sucking mouthparts.
The name “true bugs” is sometimes limited
to the suborder Heteroptera. Many insects
commonly known as “bugs” belong to other
orders; for example, the lovebug is a fly,
while the ladybug is a beetle. If it is a
true bug, the word “bug” will be separate
as in stink bug. Most hemipterans feed on
plants, using their piercing-sucking mouthparts
to extract plant sap, although some are parasitic
or predators, feeding on other insects or
small invertebrates. Many are important agricultural
pests, damaging crops by the direct action
of sucking sap or indirectly by being vectors
of serious viral diseases. Many have anti-predator
defenses by producing toxic fluids. Hemiptera
means “half wings” and they have a hemelytra
where the forewings are hardened near the
base, but membranous at the ends. They can
often be identified from other orders by the
triangular scutellum over their thorax.
These hemipterans were formally classified
in order Homoptera but are now in the suborders
of Auchenorrhyncha and Sternorrhyncha. Homopterans
differ from hemipterans by the uniformity
of their wings and the origin of their piercing-sucking
mouthparts. Homopteran forewings have a uniform
texture unlike the half-wings of their hemipteran
brothers and the winged spittlebug homopterans
hold their wings in a tent shape over their
bodies. Also, the proboscis, or beak, is on
the underside of the head capsule. The proboscis
is smaller in homopterans and they use this
beak to suck out juices from vascular plants.
The digestive system of most homopterans has
a filtering system. This allows the insect
to ingest large amounts of sap and then excrete
the excess water and sugars. Ants appreciate
this meal of honeydew and provide protection
to the insects in exchange for this sweet
meal.
This concludes this section on hemimetabolous
insects. In the next section, I will go over
insects with complete metamorphosis.

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