The Good The Bad & The Ugly

The Good - Beneficial To Humans

Hey, less than 1% of described insects in NA are major pests. Many are beneficial:

1. pollinators

	Most of our fruit, vegetable and nut crops rely on insect pollination - this grouping of food accounts for 15-30% (depends on source) of our diet. A similar portion of our diet comes from animal products - which are fed on plants that largely rely on insect pollination (McGregor, Insect Pollination of Cultivated Plant Crops). This pollination is done by 1000’s of different insect species (usually in the orders: Hymenoptera, Coleoptera, Diptera, & Lepidoptera)
	until recently wild insect pollinators were sufficient, now (due in part to insecticides & large monocultures) we raise and release pollinators (pollinators are raised for 80% of commercial crops – this is now big business)
	Excerpt from Wikipedia: Pollination management is a branch of agriculture that seeks to protect and enhance present pollinators and often involves the culture and addition of pollinators in monoculture situations, such as commercial fruit orchards. The largest managed pollination event in the world is in Californian almond orchards, where nearly half (about one million hives) of the US honey bees are trucked to the almond orchards each spring. New York's apple crop requires about 30,000 hives; Maine's blueberry crop uses about 50,000 hives each year. Bees are also brought to commercial plantings of cucumbers, squash, melons, strawberries, and many other crops. Honey bees are not the only managed pollinators: a few other species of bees are also raised as pollinators. The alfalfa leafcutter bee is an important pollinator for alfalfa seed in western United States and Canada. Bumblebees are increasingly raised and used extensively for greenhouse tomatoes and other crops.

2. as food

	for other insects, fish, mammals, amphibians & birds (50% of food consumed by North American land birds consists of insects- most land birds rear their young on insects, regardless of what they eat at other times – note that the nesting/rearing period of birds coincides with peak insect emergence
	humans - Europeans and their descendants are the only major group to not enjoy consuming insects, it is a good source of protein

Insects have played an important part in the history of human nutrition in Africa, Asia and Latin America (Bodenheimer, 1951). They were an equally important resource for the Indians of western North America, who, like other indigenous groups, expended much organization and effort in harvesting them (Sutton, 1988). Hundreds of species have been used as human food. Some of the more important groups include grass- hoppers, caterpillars, beetle grubs and (sometimes) adults, winged termites (some of which are very large in the tropics), bee, wasp and ant brood (larvae and pupae) as well as winged ants, cicadas, and a variety of aquatic insects. Ordinarily, insects are not used as emergency food to ward off starvation, but are included as a planned part of the diet throughout the year or when seasonally available. (DeFoliart, Insects as Human Food)

Since it is impossible to entirely eliminate pest insects from the human food chain, insects are present in many foods, especially grains. Food laws in many countries do not prohibit insect parts in food, but rather, they limit the quantity. People in rice eating regions, for example, typically ingest significant numbers of rice weevil (Sitophilus oryzae) larvae, and this has been suggested as an important source of vitamins.^{(Wikipedia
- Entomophagy)}

3. products

	silk - >4000 yrs silkworms have been raised domestically
	shellac - the lac scale insect occurs in India & Burma, they can totally cover a tree, lacs exude high quality resin - lac resin is processed into shellac and various other products (candy, pill coatings, etc.)
	dyes - were more in the past, now only one is commercial - cochineal dye ("natural red no. 4") is produced from ground cochineal scales found on prickly pear cactus; it is used in food additives, cosmetics and red ink
	bee products: honey, beeswax, pollen, propolis & royal jelly – royal jelly is a specialized food fed to young, can be used to treat skin disorders and in some cosmetics

4. predators / parasites

Insect predators and parasites help keep harmful insect pop’n at endemic levels - it has become a commercial enterprise; but are often ineffectual at bringing an epidemic under control

5. destroyers of weeds

herbivore insects can be reared to eat unwanted plants - especially introduced weeds (read Lord of the Weed Eaters)

6. scavengers

insect decomposers consume dead material (be it plant, animal or feces), they play an essential role as recyclers; because of this role they can provide clues regarding homicides (insect forensics)

7. scientific value

used in genetic studies, pop’n dynamics, index of environmental change

The Bad - Coming soon to a web site near you

The Ugly - Insect Structure & Function

EXTERNAL BITS

Head

1. eyes

	most have pair of compound eyes and 3 ocelli (simple eyes)
	compound eyes are large and have from one to many sensors (ommantidia), are located on top and either side of head, can perceive movement faster than human eye, gives “mosaic view”
	ocelli (vary from 0 - 3) are light sensors
	stemma (another visual organ) present only on larva with complete metamorphosis, found as a group of 1-6 on either side of head, function is between that of compound eye & ocelli, have weak form-perception - larva moves head from side to side to get “better view” (like looking through fog)

2. antennae

all insects have one pair on anterior portion of head; some antennae are greatly reduced in some spp. (e.g. those that live underground or in logs), other are greatly enhanced (“sex-charged” moths)

function as receptors for:

	tactile (touch),
	odor,
	temperature (some wood boring beetles are attuned to forests after a fire)
	humidity and
	sound

often different between the sexes (♂ antennae are more complex to receive pheromones, “hey babe, how you doin’?”)

often used for taxonomy

3. mouth parts

relates to feeding and damage; 2 types described: chewing & piercing/sucking

chewing - grasshoppers and lepidoptera larva are prime examples; mandibles move laterally (sideways); these insects bite and chew their food; mouth parts: labrum, mandibles, maxillae, hypopharynx, & labium

	labrum - “upper lip”, covers mandibles, closes the mouth in front and helps pull food in
	mandibles - 1^st pair of jaws located behind the labrum, move side ways – purpose to cut food into bite-size pieces
	maxillae - 2^nd pair of “jaws”, has “antennae-like” palps and are more for manipulating than chewing it, - purpose is to direct food into the mouth
	hypopharynx - tongue-like structure, helps manipulate food
	labium - lower lip, push food into esophagus and close mouth

piercing-sucking - proboscis is a rod-like beak (=stylet) (orders: Homoptera, Hemiptera & some Diptera)

	mandible & maxillae are reduced and often used to cut opening in host tissue (mandible cuts, maxillae inserted into new opening - repeat process until “sap/blood” is tapped into)
	the maxillae close & interlock and form 2 tunnels: salivary & food channels - saliva helps to inhibit host reaction (e.g. this helps with extraction of sap/blood as host is not able to ‘wall off the injury’)

other variations –

	siphoning (butterflies),
	sponging (house flies),
	chew & lapping of blood (many hymenoptera & diptera) – I hate these guys
	no feeding as adults (mayflies & many moths)

Thorax (for locomotion)

1. 3 segments: pro-, meso-, & meta-thorax

	one pair of legs is attached to each segment (therefore … 6 legs)
	wings (if present): 1^st pair on meso & 2^nd pair on meta
	spiracles - external slit openings for respiration, there are usually 2 pair located on the thorax (and 8 pair on the abdomen)

2. Legs - generalized leg (walking) has 5 parts (2 small ones, 2 long ones, segment section, “toes”)

coxa - basal segment

trocanter - 2^nd small segment – these two segments help to maximize range of motion (the more segments … the more flexilble)

femur (thigh) - 1^st long section = thigh bone

tibia (shin) - 2^nd long section = shin bone

tarsus (foot) - 1-5 segments at end = foot

pretarsus (toes) - pair of claws or 1+ pads = toes

functions: walking, clasping, swimming, digging, jumping

3. wings - most adults have 2 pairs of membranous wings located on meso and meta segments

	fleas, lice, spingtails, silverfish have no wings
	true flies have only 1 pair (on meso) and haltares (on meta)
	wings often used for taxonomy; elytra - adapted fore-wings for protection
	the order name often describes the wings (e.g. Diptera = 2 wings, not the usual 4, Lepidoptera = scale wing, Coleoptera = hardened wing, etc.)

Abdomen (for “guts & sex”)

	generalized: has 11 segments (some have fewer due to fusing of segments)
	a pair of spiracles are located on the sides of each of the first 8 segments
	genitalia located at posterior end

Exoskeleton

functions are:

	protection for internal organs
	water barrier
	muscle attachment
	sensory reception disadvantages:
	restricts to small size
	must be shed in order to grow making it vulnerable when molting 3 layers:
	cuticle (epi- waxy/oily waterproofing, exo- hard for strength, endo- 3^rd, thicker layer for strength & flexibility)
	epidermis is the living layer located below cuticle and produces the other layers
	basement membrane - lining that separates exoskeleton from rest of insect

INTERNAL BITS

Digestive System

divided into 3 sections

foregut (esophagus, crop & proventriculus (pre-stomach): storage and limited grinding, mixing & digestion)

midgut (stomach (ventriculus) & digestive glands: digesting and absorbing food)

hindgut (intestines & rectum: digest & absorb food, absorb water, compact and “drop”)

droppings = frass

Circulatory System

	open system (no arteries/veins)
	dorsal vessel = heart + dorsal aorta
	blood enters through slits in heart, is pumped forward through dorsal aorta into head, blood moves freely back toward abdomen
	functions: transport food, waste & hormones, also: pump up wings, lubrication of internal structures, protection (blood cells ingest or surround foreign object), coagulation
	blood in NOT oxygenated and is therefore NOT red; like Martians, insect blood is often green

Respiratory System

	air comes in through spiracles (2 pr. on thorax & 8 pr. on abdomen)
	air then moves throughout body via tracheae (air tube) and into finely-branched tracheoles (smaller tubes)
	air can be stored in air sacs to allow for “turbo power” when needed

Excretory System

Malpighian tubules absorb metabolic waste (Na & K salts, uric acid) and transport them to the hindgut (then out anus)

Nervous System

	allows rapid adjustment to environmental change
	runs along the bottom (ventral) of the insect
	consists of brain and ventral nerve cord which connects the ganglia (= a nerve bundle)
	nerves also extend from brain and ganglia to other parts of the body
	sensory organs on outside send info to ganglia - this generates motor response (i.e. flight)

Reproductive System

most require 2 sexes

but some reproduce by parthenogenesis, which means ♀'s only (therefore less beer commercials, belching and no one says "pull my finger")

♂ and ♀ bits essentially the same as mammals, exceptions, some ♀'s:

	can store sperm to allow fertilization to occur when conditions are optimal
	may have an ovipositor (“egg depositor”) located at posterior end of abdomen

Endocrine (chemical communication) System

	glands that produce & secrete hormones & pheromones
	hormones - secreted into body by one organ and produces change/reaction elsewhere, e.g. control the growth and development of an organism
	pheromone - secreted into the environment by one individual and influences behavior of other individuals, sex pheromones - ♀ produce attractants, ♂ produce aphrodisiacs (Lepidoptera & Coleoptera); also aggregation (vacancy, “come and party”) and anti-aggregation (no vacancy, “hey dude, find your own room”) pheromones