Download Insect Natural History (this is a work in progress) Insects are among

Insect Natural History
(this is a work in progress)
Insects are among the most remarkable diverse group of organisms. They occupy a
smorgasbord of niches, habitats, consume diverse diets, and can be found in aquatic, terrestrial,
and aerial. They are found in prodigious numbers, are exceptionally fecund and have rapid
generation times, both features permitting rapid evolution and adaptation on Earth. Insects have
advanced sensory and physiological systems with a complex body and yet are simple to rear in
laboratory settings. Model insects such as fruit flies have permitted greater insight and
understanding to development, modern genetics, evolutionary biology, and the integration of
body systems.
Insects interact with humans in nearly every aspect of life. Insects are responsible for the
foods we eat as pollinators of most agricultural crops. Insects are decomposers, recyclers to
clean the earth of manure and death, they filter water in streams, are pests on agricultural crops
while others are predators on these pests. They can affect human health through the transmission
of disease and serve as sentries for pollution in ecosystems. Insects provide a rich source of
protein and nutrients in those societies that routinely consume them. Through their multitude of
ecological roles, insects shape the diversity and structure of our forests.
Insects are arthropods and distantly related to crustaceans and arachnids. As such, insects
have a hardened exoskeleton made of a polymer called chitin. Interestingly chitin is also found
in the cell walls of fungi. Arthropods have jointed appendages, distinct segmented body parts
and complex mouth parts that are frequently adapted to a specific diet.
As insects grow, their exoskeleton is periodically shed with a new outer skin capable of
expansion forming underneath. Most insects have complete metamorphosis where eggs develop
into slow moving eating machines or larvae. The larvae, themselves, shed their exoskeleton
several times and grow into a new skin. A resting pupae stage interrupts the larval and adult
stages. The pupae are often cryptic, hidden, or well-camouflaged for protection while the insect
body plan is reorganized on the road to adulthood. The larvae and pupae of insects with
complete metamorphosis look nothing like the adults. In fact, larvae frequently exploit different
food sources than adults.
In grasshoppers and true bugs, metamorphosis is simple and eggs hatch into small
versions of adults that simply become larger with each molt. Dragonflies undergo a
metamorphosis that is somewhere between simple and complete metamorphosis. The aquatic
larvae of dragonflies emerge onto land as a terrestrial wingless nymph. There are no pupae in
simple metamorphosis and the adult emerges directly from the nymph.
Typically, an insect consists of a head, thorax, and abdomen. Hemolymph circulates
between the body parts as a means of transporting nutrients and waste products between the
organs. Air is delivered via a highway of tubes connected to spiracles or openings on the lateral
surface of abdominal segments. This gas exchange is direct, rather than through the aqueous
medium of hemolymph.
The insect head is invested with chemosensors, visual, and eating machinery. The neuron
-rich antennae are efficient at detecting low concentrations of specific chemicals. The eyes are
large and multi-faceted. This feature permits a 360° vision and the ability to detect movement
throughout the environment. Together, chemical and light sensor equipment permits insects to
navigate in a complex environment at high speed and great accuracy.
The mouthparts are adapted to specific food materials. Sensory palp organs pre-taste and
select food items. Chewing insects have mandibles to macerate food. Sucking insects such as
butterflies and some bugs have mandibles fused into a long tube or tongue-like structure (e.g.,
proboscis).
The thorax possesses the locomotion muscles for flight, walking or jumping. Most adult
insect possess two pairs of wings and three pairs of legs. There are exceptions and all Monarch
butterfly adults have only two pairs of legs. Monarchs and other butterflies have chemical
sensors on their tarsal pads or feet that help them identify the proper plant hosts for egg laying.
Flies (i.e., Dipterans) have only one pair of true wings. The hind pair of fly wings is modified
into mini-gyroscopes that provide stabilities to the flight of flies. Although ants have volant
individuals, the majority of ants seen in the field or forest are wingless although some wingless
tropical ants appear to perform aerial maneuvers to return to tree trunks when they are dropped
from the canopy. Insect wings may be colorful or cryptic. The beautiful wings of butterflies and
beetles can serve as mating attractants or warning indicators when insects are poisonous.
The abdomen contains the digestive system, the openings for trachea and the
reproductive organs. In stinging insects, the venom sacs and retractable stinging barbs are
housed near the posterior or the abdomen. Female insect ovipositors are located at the posterior
end to lay eggs on or within larvae hosts or environments. Some insects (e.g., Mayflies) have
elongated thread-like structures or cerci on the tip of their abdomen that are sensor organs.
There are more than 1.5 million described insect species that fall into 30 natural insect
orders. This chapter will focus on the ecology and natural history of eight of the most common
orders in eastern North America. This inclusive list will provide modest insight to
approximately 60% of the species on the planet. This groups include Hymenoptera (bees, wasps,
and ants) Lepidoptera (butterflies and moths), Coleoptera (beetles), Odonata (dragonflies and
damselflies), Orthoptera (grasshoppers, crickets, and katydids), Hemiptera (leaf hoppers, cicadas,
aphids, and true bugs), Diptera (flies and mosquitoes), and Ephemeroptera (mayflies).
Hymenoptera. Bees, wasps, and ants form a natural order of insects often distinguished
by the thin, hymen-like or membrane-like wings, and a conspicuous constriction between the
thorax and abdomen. Although a couple of groups are called “flies” (e.g., sawflies and fairy
flies), they are truly bee-like in their evolutionary history. True flies (Order Diptera) are easily
distinguished from true bees by possessing only two wings, shorter antennae, and an abdominal
width confluent with the thorax.
Bees, wasps, and ants have incredible economic and ecological value. They represent the
most important group of pollinators worldwide for wild flowering plants and agricultural crops.
In North America alone, the European honeybee is the most efficient pollinator of blueberries,
strawberries, peaches, cherries, almonds, citrus, raspberries, melons, squash, and many more.
Bumblebees are skilled and equipped to pollinate many crops in the nightshade family
(Solanaceae) and are frequently sold to tomato growers for pollination of winter greenhouse
tomatoes. Peppers, eggplants, and tomatoes require high frequency sound “sonic pollination”
to release pollen from small terminal pores on the anthers. Bumblebees sift the pollen from
Solanaceous anthers by vibrating their flight muscles at the appropriate frequency to shake the
pollen free.
Most adult hymenoptera are nectar foragers, but will also seek nourishment from
fermenting fruit and other easily accessible forms of simple carbohydrates. The diet of larvae is
highly variable. Many wasps have parasitic larvae of insects such as butterfly caterpillars.
Larvae of other bees and wasps may be provisioned with small spiders, leaf or petal parts, or
specialized adult made diet of bee bread. Mud daubers are solitary wasps that make small
underground nests encased with mud. Adjacent to the larval cells are food provision cells that
contain small spiders. The slow metabolism and requirement for meager spider provisions
allows the larvae to have fresh living food early in life.
Some members of the hymenoptera are gall makers. Galls are unusual growths on plant
organs that are stimulated by insects, viruses, bacteria, or fungi. The family Cynipidae has gall
wasps that form the oak apple galls, eastern speckled oak gall, and mossy rose galls. Other
hymenoptera gall makers include some species of sawfly.
Bee bread is a nutritious combination of pollen and bee saliva provided to developing
larvae and queens of honey bees and many bumbles. Recent evidence suggests that the
microbial community in bee bread is instrumental in improving the nutrition and preservation of
the media. Bees inoculate bee bread with the microbial fauna riding on their exoskeleton.
Microbial enzymes and antibiotics are partially responsible for the improved nutrition and longlasting shelf-life of bee bread.
The diet of ants is highly variable with carnivorous and herbivorous species and
scavengers. In eastern forests, ants are important seed dispersers of woodland herbs such as trout
lily, some violets, bloodroot, and trillium. These plants produce an accessory-like tissue
alongside seeds called eliaosomes. The word eliaosomes means “oily body” and the plant packs
them with lipids that are highly desirable food sources for ants. Ants will remove these lipid
packages for larval food in the nest and then discard the seed in a nutrient-rich organic refuse
station outside of the nest. Ants can be credited with recolonizing northern forests with
wildflowers following periods of Pleistocene glaciations.
Honey is as valuable as its weight in gold. Consider the efforts of honey bees to make a
pound of honey. Workers of the colony may travel to more than two million flowers logging
50,000 flight miles, and exerting 4000 manufacturing hours. A similar human endeavor to make
one pound of honey could cost more than 40,000 dollars after one takes into account mileage,
hourly wages, and benefits. A pound of gold
goes for a mere 12,000 dollars.
Honey possesses many human health
and medical benefits. Nutritionally, honey
contains vitamins A, B1, B2, B6, C, E and K as
well as mineral nutrients of calcium,
phosphorus, potassium, iron, copper, sulfur,
magnesium, and manganese. The low water
concentration and antioxidant qualities of honey
provide it with a very long shelf-life. The
antiseptic qualities of honey may lead to a
reduction of burn related infections. A study
performed recently in India, demonstrated that
burn wounds treated with honey experienced a
lower infection rate than burns treated by conventional means. In addition, a tablespoon of
buckwheat honey has cough suppressant qualities as great as the standard over-the-counter
concoction containing dextromethorphan.
Morphological and behavioral traits of honey bees make them exceptional flower
foragers and pollinators (Figure Honeybees). Their antennae are very good at biological
detectors of minute quantities of perfumes released in floral nectars. The high concentration of
odor detectors and the vast library of scents bees can discern permits the bees to forage with
great precision and discrimination of floral types. The forelegs of honeybees are equipped with a
special antennae brush designed to keep the pore plates of the antennae free of debris and pollen.
The bee navigates by tactile, odor, and visual cues on the flower surface to locate the nectar
reward and brush past the business part of the flower. Electrostatic bristles on the legs, thorax
and abdomen cause pollen to cling freely to the bee. While grooming the brushes and combs of
the bee legs gather pollen and then press it firmly into collections baskets on the hind legs.
A miraculous behavioral trait of the
honey bee colony is the complex
communication system. A series of forager
dancers convey information concerning the
direction and distance to the nectar source.
Floral odors clinging to the forager further
assist the bees in identifying the specific floral
source of the nectar. The honey bee waggle
dance communicates the direction relative to
the sun that a bee should travel to find nectar
(Figure Honeybees B). The waggle dance is
performed in a figure “8” pattern and the
direction the bee moves along the line
separating the two halves of the eight is the
direction relative to the sun’s azimuth. Thus if the bee returns at noon when the sun’s azimuth is
south at 180° and the nectar source is southeast (135°), then the forager orients during the
midpoint of the Figure 8 toward the southeast or 45° counterclockwise from the sun. The
distance from the hive is communicated during the waggle part of the dance. The relative
number of waggles indicates whether a bee needs to travel near (few waggles) or far (many
waggles) from the hive. While this description is rather imprecise, the information is conveyed
with great precision that tells the bees whether the nectar is 50, 75 or 100 yards from the hive.
Thus, honeybees are able to quickly find and exploit nectar sources efficient because of these
social behaviors.
While honey bees have been the subject of intense study, other members of the
hymenoptera have equally impressive navigational abilities. Recent studies indicate that ants
have similar sun compass abilities and integrate dead-reckoning to navigate along the landscape.
In addition, some species of desert ants may use an internal pedometer to return navigate to their
nest. The later was demonstrated by artificially shortening or lengthening the legs of ants that
had navigated from the nest. Those making the return with shortened legs, and hence had
smaller steps, stopped short of their intended goal while those with lengthened legs walked past
the nest.
Bumble bees are social like honey bees, but their colonies follow an annual, rather than a
perennial, cycle. Queen bumble bees overwinter and emerge in the spring to lay eggs in dry
patches of grass, soil, wood, or gravel. Workers develop from these eggs to construct the nest.
Males and additional queens form in late summer, mate, and then the queens once again over
winter to repeat the cycle. Worker and queen bumble bees can be found most of the spring and
summer. They are easily distinguished from late season males, by possessing six, rather than
seven, abdominal segments, shorter antennae and indentations serving as pollen baskets on hind
legs.
More than ¾ of North American bees are solitary species. These species make individual
nests occupying tunnels in wood, underground chambers, and tunnels. Nests of solitary species
may be aggregated, but the bees do not exhibit social behaviors with one another. In leaf cutter
bees, leaf or petal pieces are used to construct the nesting structure. Some solitary bees utilize
vacated tunnels of wood boring beetles while others use mud and wood fibers for nesting
materials. Orchard managers are becoming more adept at managing for solitary bees as they are
an important natural tool for crop pollination when and where honey bee hives have been lost.
Despite their painful sting, bumble and honey bees are remarkable easy to handle given a
little bit of knowledge and care. Both groups are easily captured using butterfly nets, but the
transfer of a frustrated bee to a collection container can be a challenge. It is far easier to use a
small glass container to enclose a flower foraging bee and then gently slip the screw on top over
the container. A short chill down in a refrigerator or a cooler with ice will allow the bees to be
handled for a few minutes until the bee re-warms and then flies away.
Lepidoptera (Figure Lepidoptera). The
exoskeleton, in particular the wings, of butterflies and
moths are covered in minute, rectangular shaped scales.
Hence the name of this group is scale-winged or
Lepidoptera. Worldwide there are 150,000 species of
Lepidoptera. Nine out of every ten species is considered
a moth and there are probably many more left to be
discovered. Butterflies are largely diurnal species as
adults. Moths may be active at any time of day or night
although the tendency is to be crepuscular (i.e., active at
dawn or dusk) or nocturnal. Butterfly antennae are most
often club shaped with the terminal end knobby or
enlarged. Moths have antennae that are feathery or thin
and gradually reduced to a tapered tip. Moths tend to be
bristlier than butterflies and hold their wings flattened
over the body.
Butterflies and moths undergo complete
metamorphosis with distinct larvae and pupae. The caterpillars are ravenous foragers and shed
their skin multiple times (4-5 instar stages) to grow larger. For example, the monarch butterfly
caterpillar hatches from an egg weighing less than 1 milligram. Within two weeks, the
caterpillar has increased its mass some 2000x with a final weight of more than 2,000 milligrams
(2 grams). During that time, the caterpillar is an eating and defecating machine.
For Monarchs, the fifth instar caterpillar will leave the milkweed plant find a suitable
resting point and spin a circle web of silk from modified salivary glands to attach itself. The
caterpillar relaxes into a J-shape and within a few hours its skin starts to split near the hanging
anterior region. The caterpillar gyrates, further splitting the skin and pushing the blackened mass
toward the tail. The green, amorphous interior of the caterpillar contracts into a beautiful
chrysalid. In a matter of minutes one can watch the resting caterpillar shed its skins and expose
the chyrsalid with the underlying blueprints of an adult Monarch butterfly. One can see the
segments of the abdomen, the linear legs, the wings, and the two strips of proboscis in the newly
formed chrysalis. In the evening on about 10th day, the chrysalid will transform into the color of
the adult butterfly that will likely emerge the following morning. The emerging butterfly is
anything but beautiful. The wings wrap the thorax and abdomen in a cloak. The large distended
abdomen contracts in peristaltic waves pumping hemolymph into the wings which enlarge and
harden. The two slivers of proboscis are zipped into one coiled tube that becomes an effective
nectar siphon. The adult butterfly is ready to assume a different ecological role as a nectar feeder
among flowers.
Butterfly and moth species most frequently specialize as herbivores on a small group of
flowering plants. Monarch caterpillars eat milkweed, meadow fritillaries eat violets, spicebush
swallowtails eat members of the laurel family, eastern tent caterpillars eat members of the rose
family, the catalpa sphinx moth eats catalpa and so on. Distantly related plants manufacture
different chemical toxins. It is easier in a biochemical and evolutionary sense to specialize to
one book of toxins than the entire library found in land plants. Female butterflies sense,
recognize, and use plant toxins to identify the appropriate plant host. Caterpillars may use the
toxins to stimulate feeding. Generalists are rare, but they do exist. The common wooly bear
(Pyrrharctica isabella) eats just about any low growing herbaceous plant.
Caterpillars are vulnerable to attack by insectivorous birds. They are slow moving bags
of concentrated nutrition. Many strategies have evolved to provide protection. Caterpillars often
hide on the underside of leaves and move about more readily under the cloak of darkness. Many
species are cryptic and resemble dead leaves (curve-lined owlet), twigs (purplish brown looper),
petioles (grapevine looper), lichens (Ilia underwing), snakes (spicebush swallowtail), or bird
droppings (viceroy). Many tropical caterpillars have eye spot and segmental patterning
mimicking snake faces to threaten would be predators of the caterpillar. Saddleback and Io moth
certainly provide protection in nature.
Winter survival strategies are diverse in butterflies and moths. Most butterflies
overwinter as eggs, larvae, or pupae with relatively few species overwintering as adults.
Mourning cloak, tortoiseshell, and question mark butterflies survive as adults. The mourning
cloak can be seen flitting through forests in early spring and on warm winter days. Adults seek
shelter in crevices of bark, wood, or rocks. Mourning cloak hemolymph remains fluid through
the winter as sugar and sugar alcohols (e.g. sorbitol and propylene glycol) act as antifreeze.
Adult butterflies can take flight only if their flight muscles are 95°F. This is accomplished by
two methods. First, the butterfly will bask in sunlight with the dark inner wing surfaces exposed
perpendicular to the sun’s light. Second, small deposits of brown fat are found near the flight
muscles. As in some mammals, brown fat is thermogenic and has the capability of raising flight
muscle temperature along with rapid vibration of the flight muscles.
Relatively few butterflies use migration as a means of escaping winter and utilizing
seasonably rich summer food resources in temperate areas. While the Monarch butterfly has the
most well-known migratory behavior, migration has been reported in sulphurs, buckeyes, red
admiral, and painted lady butterflies. These butterflies have various degrees of cold tolerance
and repopulate much of eastern North America each summer in a one-way mass movement.
Monarch butterflies belong to a tropical lineage of butterflies and are not freeze tolerant.
In eastern North America, their annual migration tracks southward in the autumn toward the
Sierra Madre Mountains of Mexico only to return to the eastern States the following spring.
Adult monarchs seek refuge in the Oyamel fir forests above 10,000 feet. The evergreen cover
protects monarch butterflies during freezing weather and allows them to rest most days at a
moderate temperature that slows metabolism. The butterflies aggregate and form colorful
drapery along the branches and trunks of the firs. Over the past decades, human encroachment
from subsistence wood harvests and farming has exposed these winter refugia to cold weather
and snowstorms that can kill millions of monarchs.
No single monarch makes the entire migratory trip. Butterflies leaving Mexico in March
arrive in southern states finding spring milkweeds where they mate, lay eggs, and then die. The
northward migration is continued by the next generation of butterflies. In central NewYork,
monarch butterflies begin to arrive in early June. A second breeding generation of butterflies
develops and by middle August the southward migration of non-breeding adults begins. While
there are many unanswered questions regarding the navigational skills of monarch butterflies, it
is remarkable that these individuals of this species find the same small Mexican refugia of their
ancestors three generations removed from the previous year. Time-shifted monarch butterflies
have demonstrated that adults rely on the time of day and position of the sun to navigate towards
the Mexico. Nevertheless, this sun compass must have other undiscovered mechanisms that
allow those butterflies in the east to migrate on a heading that is more westerly than those in the
Midwest.
Lepidopterans exert their greatest economic impact as herbivores on crops and forests.
The corn ear worm is among the worst in the United States by attacking sweet corn, tobacco, and
tomatoes in southern states. The adult corn ear worm moth lays eggs on the silk of the female
corn tassels. The larvae develop within the protective sheath of the overarching tassel leaves
only to be discovered some time later by an eager corn lover. Control of the corn ear worm
requires adequate well-timed application of pesticides. Biotech firms have developed several
lines of corn that have been genetically engineered with genes from the bacterium Bacillus
thuriengiensis. The engineered Bt corn then produces bacterial toxins that help control the ear
worm populations with fewer applied pesticides.
The gypsy moth is an Old World species that was accidentally introduced to eastern
North America on multiple occasions (1869 and 1991). Gypsy moth caterpillars are voracious
eaters of oak, poplar, maple, and birch leaves and can have a devastating effect on eastern
forests. Their eggs are timed to hatch close to the maturation of spring leaves. Without natural
checks and balances by predators and disease, the gypsy moth caterpillars can defoliate every
leaf of an oak forest in a few weeks. In mid June and July, ghost forests and oak skeletons can
be found up and down the Blue Ridge Parkway in Virginia. Repeated defoliation of trees could
result in tree death, as the weakened trees become more susceptible to parasitic fungi and insects.
Thus, gypsy moth invasions may reshape the forest biodiversity by increasing tree species more
resilient to gypsy moth predation.
The Forest tent caterpillar undergoes periodic natural outbreaks in eastern North America
defoliating large tracks of maple, oak, birch and elm forests. Curiously, forest tent caterpillars
don’t eat red maple which standout among largely defoliated forests. In outbreak years, the
biomass of forest tent caterpillars exceeds that of any other animal per unit of area. Naturally
occurring viral and bacterial pathogens as well as avian predators help to control this native
species and therefore limiting is destruction over a long period of time. Nonetheless, this species
may also shape the biodiversity of tree species in eastern forests.
Orthoptera (Figure Orthoptera). Crickets, grasshoppers, and katydids are among the
best known insect singers of temperate North American summers. The group is identified by
their strong hind-legs and enlarged “femur-like” upper leg that provides great jumping ability.
The forewings of orthopterans are stiff, narrow, and long. The hind wings are folded together
like a fan at rest, but become the main lift and thrust generators of flight. Some grasshoppers
like the Carolina locust perform hovering flights as part of their premating displays.
Nearly all members are herbivores with chewing mouth parts, but most broaden their
dinner plate with a few insects. Locusts are large herbivorous grasshoppers that exert a major
impact on forage crops, grains, and canola in desert areas of Africa and Australia. Locusts form
large swarms or plagues in some years and can completely annihilate crops in short order. Like
many grasshoppers, locusts are food generalists and tolerate the complex chemistry of most
groups of flowering plants. In Athens Georgia, lubber grasshoppers frequently invaded summer
gardens. The lubbers could eat any and all of our cherished plants and thin rub your nose in it by
posturing in an intimidating way by showing their large red hind wings. Try to capture these
guys by hand and they emit a smelly froth on your hands.
Orthopterans are one of the orders of insects with incomplete metamorphosis. Eggs hatch
into smaller versions of the adult that become progressively larger and winged with reproductive
organs. These small developmental stages are referred to as nymphs. Nymphs eat and behave
much like the adults.
Crickets and katydids are best known for their evening chirps, clicks, and songs of the
middle summer. Insect songs serve to attract mates, but may also have a defensive vocabulary in
maintaining a territory. The cricket or katydid song is produced by rubbing two hardened
exoskeleton parts together. In most cases, a hardened vein that runs near and parallel to the base
of the forewing is lined with ridges. A scraper on the hind wing or legs is drawn against the
“file” vein on the forewing to produce sound much like dragging a finger across the teeth of a
hard rubber comb. The thin membranous components of the wing act as tympana to resonant or
amplify the sound. The frequency of cricket singing is correlated with ambient temperature.
Presumably, one can construct and insect thermometer by determining the frequency of chirping
across a range of temperatures for a given species. In crickets and katydids the tympanum is a
small oval of flattened member on the upper portion of the lower first pair of legs. The
tympanum of grasshoppers is small semi-circular window on the lower surface of the first
abdominal segment. In both cases, auditory nerves near the tympanum allow many orthopterans
allow the insects to hear the songs of their potential mates or competitors.
Odontata (Figure Odonata). Dragonflies and
damselflies are large menacing looking insects with long
abdomens, and four clear, membranous wings of similar
size. Their heads are ornate with small-bristle-shaped
antennae and disproportionately large eyes. The size and
lateral position of these predator eyes gives them 360°
vision. Dragonflies hold their wings flattened at rest and
the base of the hind wings is broad. Damselflies, on the
other hand, hold their wings above the abdomen and the
hind wings narrow to the base. Both groups are
predators of small flying insects. Dragonflies and
damselflies are most often associated with aquatic
habitats, although one can find dragonflies the top of
Adirondack peaks and frequently in gardens.
Dragonflies copulate in flight while damselflies prefer a
more restful position on vegetation.
Dragonflies and damselflies are important
components of a healthy aquatic ecosystem. They
undergo simple metamorphosis with the nymphs entirely aquatic, but then emerge and split their
exoskeleton to become a winged terrestrial adult. The nymphs are well-camouflaged and quick
moving predators. Dragonflies have internal gills at the tip of the abdomen. They contract
abdominal muscles to move water across their posterior gills. This mechanism also serves well
for emergency escapes as quickly squeezed abdominal water is an excellent form of underwater
propulsion. In contrast, damselflies possess three thin gills off the tip of the abdomen. However,
pollution sensitivity varies and a multi-species analysis provides the best indication on water
quality. Odonata are pollution sensitive and good indicators of healthy aquatic ecosystems.
Nymphs are the top macro-invertebrate predator in the aquatic ecosystem.
Fossil ancestors of Odonata are well-known from the carboniferous period (325 MYA)
and obtained sizes up to 75 cm in length. This group of ancestors declined near the appearance
of the dinosaurs with more modern species appearing 250 million years ago. Although adult
forms have changed little in the past 200 million years it is unclear whether the first Odonata had
aquatic larvae as they did not preserve well in the fossil record.
Mating is an unusually complicated and energy intensive practice in dragonflies. Male
dragonflies produce sperm near the tip of their abdomen, but must transfer the sperm to the
copulatory organ closer to the thorax. Males grasp females by the head and thorax, but then
bend the tip of the abdomen upward to grasp the female dorsally behind the head. While flying
in tandem under the power of the male, she must bend the tip of her abdomen upward to clasp
the copulatory organ near the male’s thorax. The copulatory organ of the male is used to remove
or push aside the sperm of other males prior to depositing his own. Although actual copulation
lasts from a few seconds to more than an hour, the male will likely fly considerably longer in
tandem with the female to ensure that his sperm fertilize her eggs. In some species, the male
patrols the female and keeps a watchful eye out for male competitors looking for additional
action.
Like locusts, dragonflies are known to form large migratory swarms in autumn and fall
on every continent except Antarctica. Recent radio tracking by Wilkelski, demonstrated that
green darners follow a few simple migratory rules that parallel that of songbird migration.
Southbound green darners tagged near Princeton flew only after fat reserves had been garnered
and on days following two successively cool nights. In addition, the reoriented near Cape May
New Jersey to fly inland in lieu of flying across Delaware Bay. Migrating darners and skimmers
appear not to make the entire round trip as those returning to northern states in the sprint appear
to have fresh, unworn wings.
Homoptera/Hemiptera (True Bugs, Hoppers and Cicadas). The Hemiptera is a large
diverse group that now includes members of the former order Homoptera. Suborder Heteroptera
includes the true bugs such as water striders, water boatmen, assassin bugs, and stink bugs. The
wings of this group are held flat at rest and are slightly thickened at the base. Many members
plant parasites and suck plant juices through beak-like structure on the head. Water boatmen and
water scorpions are predators on other insects in an aquatic environment. They are fast moving
and capable of navigating quickly in slow moving water of stream pools and ponds. Assassin
bugs are frequently camouflaged in vegetation and on flowers and are capable of capturing and
overcoming insect prey several times larger than themselves.
Suborder Auchenorrhyncha include cicadas, leaf and tree hoppers, and spittlebugs.
Members hold their wings in a dome or roof over the thorax and abdomen. All members are
plant feeders and often cause significant damage on trees or
crops.
The periodic cicadas are well-known for their
unusual 13 or 17 year life cycle and for their massive
emergence and noisy buzz-like male songs (Figure
Cicadas). Males make songs from membrane-like tymbals
that stretch across the first segment of the abdomen.
Muscular contraction of the tymbals produces sound that is
amplified by the large hollow abdomen. Cicada nymphs
emerge quickly from the soil, shed their skin, emerge as
adults and mate in a well-timed event. The females
oviposit their eggs into young woody twigs. Egg laying
usually causes the twig to die, break from the tree and fall
to the ground. The nymphs dig into the ground and feed off
of plant juices from the roots for the next 13 or 17 years.
The emergence of cicadas is so massive that many species
of birds engorge themselves on the adults. Adventurous
humans may eat cicadas in stir fry, pizza, quiche, or any
number of other ways. Assuming that they are safe to eat, cicadas are high in protein, low fat,
with no carbohydrates.
Leaf, plant and tree hoppers are very common small insects with an incredible leaping
ability. Some members are known to jump forty or more body lengths in a single leap. The size
and cryptic coloration of many hoppers make them difficult to find with the human eye.
Spittlebug nymphs are fairly obvious in that they whip-up white foam along plant stems
protecting them from potential predators. Many hoppers make sounds by vibrating their
abdomens against plant parts. Unlike cicadas, hopper sounds are usually inaudible to the human
ear.
Aphids are slow moving sucking insects that live on soft stem tissues of plants. Aphids
are particularly adept at using their stylet to penetrate stem tissue and find the sucrose rich sieve
tube members. Plant physiologists have made great use of the stylets to examine the contents
and pressure of phloem sap. The microflora of aphid digestive system is very important at
metabolizing carbohydrates to make amino acids and other organic molecules that the aphids
require for life. Aphids obtain more than enough sucrose from the plant and must excrete
“honey dew” from the end of the digestive system. The sucrose rich honey dew is a powerful
attractant to ants and lady bug beetles that tend to the aphid colony. The ants and beetles are
fearless and aggressively attack any potential predator. The majority of the aphid population on
a plant is composed of wingless adults, although some generations produce winged individuals
that disperse to more plants or an alternate host.
Scale insects are an unusual group, not just for bugs, but for insects in general. Scales
mature as slow creepers on plant stems to become a rounded insect impacted in a waxy secretion.
Adult females become immobile as the legs are lost or more appropriately reabsorbed by the
body. Adults remain attached to the plant slowly draining the plant of sap. Scales are a
gardener’s nightmare because the waxy covering sheds most aqueous based pesticides. Toxic
oils are frequently applied to suffocate and poison the insect.
There are two economically important scale insects worth mentioning. Laccifer lacca is
the shellac scale. Female lacs secrete an orange resinous material to cover their bodies on
tropical figs of Indonesia. The massive numbers of scale insects and the thick coating of resin
make the material collectable. Shellac is water resistant, durable, and resistant to organic
solvents. It is non-toxic, easy to handle, and adheres to most intended surfaces. Shellac can also
be found in pharmaceutical grade and confectioner’s grade glazes. In pharmaceuticals, shellac
can be used to coat medications, especially those of slow or time-released capsules and pills.
Confectioner’s glaze is used to smooth and shine chocolate products and some colorful candies.
Junior mints, milk duds, and Mike n’ Ike are a few candy products coated with confectioner’s or
resinous glaze to preserve freshness and maintain the proper moisture content.
The cochineal scale is a prickly pear cactus specialist in South and Central America.
Unlike lac scale, the waxy secretion of cochineal scales is not the used product. Instead the
crimson colored pigment is found inside the scales and as an extremely bitter material it likely
functions as a chemical protection against predators. Carmic acid is extracted from cochineal
scales and made into carmine. This product has been used in cosmetics (rouge and lipstick),
fabrics (British Red Coats), juices, and food and some pharmaceuticals.
In South and Central America, the kissing bug or triatomine bug is a carrier of this
devastating protozoan disease (Trypanosoma cruzi) called Chagas disease. The disease is
transmitted when the kissing bug bites a human and simultaneous excretes near the bite. The
concomitant itching infects the blood stream with the trypanosome. The disease can cause lifethreatening heart arrhythmias, enlarged hearts, and swollen esophagus and colon. Chagas
disease is common in rural Latin America, but in recent years it has entered the United States
through international travelers. It has been hypothesized that Charles Darwin suffered from
Chagas disease as his diary from the Beagle travels suggest he was bitten by the kissing bug near
the Andes Mountains of Argentina.
"At night I experienced an attack (for it deserves no less a name) of the Benchura
(Vinchuca), a species of Reduvius, the great black bug of the Pampas. It is most
disgusting to feel soft wingless insects, about an inch long, crawling over one's body.
Before sucking they are quite thin but afterwards they become round and bloated with
blood."
Coleoptera. The British population geneticist, J.B.S. Haldane, once responded that the
Creator must have “an inordinate fondness of beetles.” One of every four insects is a beetle, and
more beetle species have been named than any other group of organisms. Beetles are easily
identified by their thickened forewings (i.e., elytra) that meet at the dorsal midline of the thorax
and abdomen that are used to protect the hind wings and abdomen while at rest. The elytra is
often iridescent or decorated with bright colors and conspicuous markings. Fireflies, ladybug
beetles, whirligigs, and Japanese beetles are a few of the most easily recognized beetles in the
Northeast.
Beetles have diverse ecological roles from that of plant parasites, dung and carrion eaters,
wood borers, scavengers, carnivores, and decomposers. Beetles have complete metamorphosis
and their larvae often have different ecological roles than the adults. Blister beetles are nectar,
pollen and flower eaters while their larvae are parasites on bee larvae or grasshopper eggs. Lady
bug beetles are well known as aphid eaters and are often sold to greenhouse managers as part of
an integrated pest management strategy.
Fireflies are neither flies nor are they on fire. In fact, their light producing abilities are
extremely efficient and emit no heat. Fireflies control the frequency of their abdominal flashes
by regulating the amount of oxygen flowing into their abdominal chambers. When the firefly
molecular luciferin is in the presence of oxygen, the enzyme luciferase, and ATP light is
produced. Males flash at a rate that is species specific as a visual love song to females. Females
are flashers too and respond with their own flash to displaying males.
An interesting biochemical evolutionary story involves two groups of fireflies. Photinus
fireflies produce a steroidal chemical, lucibufagin, that is a bitter deterrent to potential predators
such as birds and reptiles. Birds may recognize Photinus fireflies as bad tasting and leave them
alone. On the other hand, Photuris fireflies lack chemical protection, but females have acquired
a nifty trick to protect themselves and their eggs. Photuris females will respond to Photinus
male flashes and attract them under the false pretense of mating. Instead of copulation, the
Photuris females kill and devour their male victims. This fatal attraction allows the females to
acquire lucibufagins, store them for their own protection, and allocate these chemicals to their
eggs.
Whirligig beetles are aquatic predatory beetles of ponds in our area. Whirligigs carry an
air bubble on the lower surface of their abdomen and the surface structure of their exoskeleton
permits a thin boundary layer of air to travel underwater. This film of air gives the whirligig’s a
silver appearance while swimming. Flipper-like hind legs and a smooth aerodynamic profile
gives these insects great maneuverability in an aquatic environment.
The woods of eastern North America are currently under attack by two exotic beetles.
The emerald ash borer (Agrilus planipennis) was first reported eating ash trees of southeastern
Michigan and adjacent Canada in 2002. It has spread quickly and has now been reported from
Minnesota to New York and southward to Missouri and Virginia. Eggs are laid deep in the bark
of ash trees (Fraxinus) and threatens to kill all ashes in urban and native forests.. Larvae feed
inside the bark on the soft cambium and destroy the tissue for secondary growth. Trees usually
succumb two years after attack. The Asian long-horned beetle (Anoplophora glabripennis) may
pose a similar threat to many more species of plants. Although it was discovered in NY city in
1996, it appears to be quarantined to areas of Chicago and New York City. The viburnum leaf
beetle (Pyrrhalta viburni) wreaks similar havoc on native viburnums shrubs. This European
species was first discovered 1947, but has recently had a profound impact on the viburnums of
central New York by killing many of the V. nudum and V. dentatum in our forests. Together
these species have brought about policy changes on the movement of firewood throughout the
Midwest and Northeast in an attempt to quarantine these insect pests.
Ephemeroptera are aptly named for their short-lived adult life stage. Mayflies emerge
from the water as a winged subimago, shed their exoskeleton to become a brighter, more active
adult or imago. The adults live on the order of a few hours to a day or more. Adults are devoid
of developed mouth parts and a digestive system. The sole purpose of adult mayflies is to find
each other, mate, and then for the females lay eggs. Mayflies hatch in large, well-synchronized
blooms during spring and summer. They are easily identified by their long abdomen, long
terminal cerci, and triangular-shaped wings held high above the thorax and abdomen. The wings
are conspicuously veined. Mayflies can be intriguing to watch in flight as they often have short
parachuting descents with a rapid, powered ascent. Many song birds gorge themselves on
mayflies from window screens on homes and buildings during a large hatch.
Mayflies are important biomonitors for stream, lake and pond health. The larval nymphs
are long-lived organic feeders with abdominal external gills. Each species has precise habitat
requirements and sensitivity to water pollution. Some mayfly nymphs burrow into lake and pond
sediments. This has the impact on aquatic ecosystems by constantly disturbing and circulating
polluted sediments to the water column. Several species of mayfly were once extremely
abundant throughout the Great Lakes. Industrial discharges lead to the loss of the once dramatic
mayfly hatches during the 1960’s. Only recently have large mayfly hatches returned to some
areas of Lake Erie which was once believed to be terminally polluted.
Mayflies are one of the model insects used in fly fishing. Skilled fishermen tie their flies
of feather or animal fur to mimic subimago, imago, or dead mayflies. The successful fisherman
will tie flies to mimic the coloration and shape of mayflies as seen from below the water. The
delivery of fly and the pulsing action of the pole mimics the behavior of the insect to capture the
attention of fish. Because many fish feed on the most temporally abundant prey, the fisherman
must also know the specific species of mayfly and match the tied fly to the species specific life
stage.
Diptera. Flies, gnats, and mosquitos are among the most dangerous insects to humans.
Several flies, and mosquito species are secondary hosts and responsible transmission vectors of
viral and protozoan diseases such as typhoid, malaria, dengue fever, malaria, and many forms of
encephalitis. While many of these diseases are tropical where mosquitos and flies do not have
seasonal periods of freezing weather, many of these diseases have had outbreaks over the past
two centuries as a result of shipping tropical products of large movements of humans into
temperate zones. In areas of Africa, black flies are one transmission vector for round worms that
cause river blindness (onchocerciasis).
Despite their bad reputation as disease vectors, dipterans are diverse and fulfill many
ecological niches. Four species of Wyeomia mosquito develop in the aquatic community of
pitcher plants and even over winter frozen in the pitcher water. The famous South and Central
American bot fly captures and lays eggs on the abdomen of female mosquitos. Heat from the
blood meal mammal of the mosquito triggers the bot fly egg to hatch, crawl into the mammal fur
and burrow in the skin where it will develop over a two-three month period. Unwary travels to
tropical America frequently return home with large unexplained welts that itch and cause
occasional pain as the larva move about in the skin. Many dipterans are decomposers where
their larvae feast and develop in carcasses or manure. The ability of some fly maggots to
meticulous clean decaying flesh has brought about new medical treatment to prevent infection
post surgically. Medical Debridement Therapy utilizes sterile maggots of the green bottle fly to
clean wounds. The therapy promotes healing and seems to thwart many infectious bacteria from
invading the wound. Historically, indigenous Central and South Americans have likely used this
therapy for millennia.
Flies are often confused with hymenoptera. Syrphid flies are well known mimics of bees,
wasps, and yellow jackets. Unlike hymenopterans, dipterans have a single pair of flight wings.
The hind pair of wings has been modified into small knobby sticks that act as mini-gyroscopes
for stability in flight. These halteres are small and difficult to see in many groups, but are large
and obvious in crane flies. Dipterans also have large eyes and shorter antennae. The abdomen
of most flies in confluent with the thorax and lacks a distinct constriction as found in
hymenopterans. Flies have sucking mouth parts whereas bees and wasps have chewing mouth
parts.
Metamorphosis is complete in dipterans, but the metamorphosis can occur in different
media. Black fly, midge fly, and mosquito larvae develop in aquatic ecosystems and feed on
organic matter. Mosquito larvae breathe from the surface and use a special abdominal breathing
tube. Manure and carcass decomposers have larvae that develop quickly to utilize the shortlived food source. Eggs of the African tsetse fly and a few others actually hatch internally and
live within females until the larvae are ready to pupate.
Other curious insects. Earwigs (Order Dermaptera) are nocturnal scavengers and plant
eaters, but are almost never found wiggling out of one’s ear. The cerci are sharply hooked in
dermapterans and can inflict a painful pinch if miss-handled. Silverfish (Order Thysanura) are
commonly found in human dwellings and libraries. Warm recesses of basements near the
furnace are great locations to find firebrats while silverfish prefer dampness and cool
temperatures. Silverfish enjoy diets of starch and cellulose. Even in the absence of intestinal
microflora, silverfish produce cellulose and have little trouble digesting cellulose. Thus,
silverfish can be a librarian nightmare by eating the paste of book bindings. Other cellulose
digesting insects are only able to exploit this molecule because their intestinal microflora are
capable of producing cellulose.
Termites (Order Isoptera) are well known for their wood devouring capabilities due to
their intestinal microflora with cellulose digesting machinery, but it is seldom appreciated that
termites have had a role in Australian music. The Didgeridoo is a musical instrument
constructed of a long pipe of Eucalyptus wood bored clean by termites. Add a mouthpiece of
beeswax, another hymenopteran product, and the drone pipe or digeridoo becomes a deep
vibrating aerophone common to aboriginal music. The Aphex Twin (Richard James) is a
celebrated English music maker who reproduced the sound of the digeridoo from drain pipes to
produce a popular instrumental piece called “Digeridoo”.