Insect Diversity Terminology 2nd Half

What are the main functions of the alimentary canal?

Ingesting and breaking down food, absorbing nutrients, removal of feces

What are the tree sections of the alimentary canal/gut? 

Stomodeum (Foregut), Mesenteron (Midgut), Protodeum (Hindgut)

What is the role of to Stomodeum

Preliminary breakdown of food, production of digestive enzymes

What organs make up the Stomodeum

Preoral Cavity, Pharynx, Salivary Gland, Oesophagus, Crop, Proventriculus

What is the purpose of the crop

Storage of food

What is the function of the proventriculus 

Grinding and crushing food, the proventriculus is very muscular and has teeth lining it to aid in breaking down food 

What is the role of the Mesenteron

Absorption of nutrients

What organs make up the Mesenteron

Gastric caecum, Ventriculus, Peritrophic Membrane

What function do the gastric caecum serve?

Help with absorption

Describe the Ventriculus

Lined with a thin, paratropic membrane, the ventriculus is very permeable allowing absorption of nutrients into epithelial cells while storing plant material and bacteria

What is the role of the proctodeum

Removal of waste products

What organs make up the protodeum

Malpighian tubules, ileum, colon, rectum

What is the function of the Malpighian tubules

Reabsorb water and nutrients before excreting waste

Insect feces

frass

What are the two variations in foregut morphology

Generalized orthopteroid (plant eating) and Xylem-feeding hemiptera (liquid sucking)

Name 4 differences between the Generalized Orthopteroid and Xylem-feeding hemiptera foregut characteristics

• The two have different musculature (there is more developed musculature in the hemipteran)

• The crop is much larger in the orthopertoid

• The hemipteran has much more developped salivary glands

• The hemipteran also has adaptations for piercing and sucking

What is the function of the cibarium and what order is it found

Found in xylem-feeding hemipterans, it is used to suck up food when it is tensed and push it through into the gut when it is relaxed

What is the role of gut microbes

Produce pigments, breakdown toxins, supply nutrients, and aid in absorption

What are two examples for how insects can use the alimentary canal in a form of defense

Regurgitation (with sound warning), and frass flinging

How does gas exchange work in Insect tracheal systems

Gas exchange occurs through diffusion, some insects have some level of pumping to circulate air

What are taenidia

Spiral cuticular thickenings of the trachea that keep the tubes from collapsing (similar to a ribbed vacuum hose)

Where does the air enter the tracheal system?

The spiracles

What is an open tracheal system

Spiracle to the outside of the body

What is a closed tracheal system

Spiracles are absent, instead tracheal network lines the body surface to allow cutaneous gas exchange

Where is it common to find open tracheal systems

Terrestrial and Aquatic insects

Where is is common to find closed tracheal systems

Some aquatic insects and endoparasitic larvae

What is hypertrophy (in terms of tracheal system specializations)

When insects increase tracheal surface areas in oxygen poor environments

How does the Walnut Sphinx moth use it’s tracheal system as an antipredator defense

It whistles when it is attacked by contracting it’s anterior body, there is a special spiracle located in the 8th abdominal segment

What is the main role of the circulatory system

Transport nutrients, hormones, waste, provides immunity and hydrostatic pressure

What does the circulatory system in insects NOT do

Insect circulatory systems do not transport gases

What is insect “blood”

Haemolymph

Where does the haemolymph circulate

Within the haemocoel

Describe the type of circulatory system found in insects

Open, the tissues are bathed in haemolymph

Where does the circulatory system open

The circulatory system is open at anterior end and closed at posterior end

What are some examples of specialization of the circulatory system

Osmeteria (Use of hydrostatic pressure to extend tubes from head), Reflex bleeding (Force haemolymph from part of appendages ex. blister beetles and cantharidin), Wound healing (get rid of bacteria with phagocytes and white blood cells)

Insects have ganglion (brains) throughout their body, but why is there a larger accumulation in the head?

There are more sensory need located in the head such as sight, taste, and smell

What is the function of the endocrine system

Production of hormones and neuromodulators

What processes are a result of the hormone production in the endocrine system

Molting, Metamorphosis, Reproduction, Feeding

What is Ecdysone

A molting hormone released by the prothoracic gland that controls when an older instar can begin molting or undergo metamorphosis

What is juvenile hormone

Released by the corpus allatum, the juvenile hormone can inhibit metamorphosis in juveniles (and as a result it is often used in pest control)

What is the role of the accesory gland in male and female reproductive systems

In females the accessory glands produce and add substances to the eggs (such as waterproofing, glue, nourishment, and cement, venom). In the male accessory glands are responsible for sperm support and female manipulation

What us the spermatheca

Storage organ for sperm in the female, this organ can hold on to sperm for very long periods of time

What is the definition for attraction in insects

Species-specific signals produced at a long range to bring the sexes together (Can be sounds or pheromones and are generally less variable within a species)

What is courtship in insects

Close-range signals and behaviours that lead mate choice and copulation (are usually more unique to the individual, and can be indicative of male quality)

How come courtship signals influence female choice

Small, parasitized individuals may not be able to create that good of a song

Explain the phenomenon of Mating Swarms involving Arctic Flies and Mosquitos

Male arctic flies will find a swarm of mosquitos and pick out one to give to a female as a nuptial gift. The female will assess the quality of the gift and if it is to her satisfaction the two are coupled and can mate as the female eats the nuptial gift

Describes the role of Sex Pheromones in Moths

Sex pheromones are produced by moths for long distance attraction (~2km). A female will release pheromones so a male can find her. The male will detect the pheromone and locate the female by following the scent in a wave-like flight pattern

Do male or female moths have larger antennae?

Male moths have larger antennae (and are often more elaborate in shape) to help them locate females

Describe Bark Beetle Courtship

First, female beetles will attract males to a tree using pheromones. The females begin to build their gallery in the bark. Males will begin to chirp at the female, each individual male having their own chirp. The chirps will become increasingly more energetic as they compete for the female’s acceptance. Females will choose the male with the more energetically costly chirp as that male is likely healthy and strong

What are direct benefits when in comes to female choice in courtship

Protection (large and strong males can offer better protection from predators), and Food (often nuptial gifts are some sort of consumable such as a mosquito in the case of arctic flies, spermatophylax in the case of katydids, or self sacrifice)

What is a spermatophore

Capsule containing sperm that is transferred to the female

What is the spermatophylax

The proteinaceous part of the spermatophore that the female can eat as the sperm is being transferred to her spermatheca

What is sexual canabalism

Female eats part of the body of the male she mates with (Ex. grasshoppers that eat the top part of the abdomen or Redback spiders where the male flips into the females mouth parts during copulation)

What are indirect benefits when it comes to female choice?

Offspring will inherit positive traits from chosen male

What is sperm competition

Occurs post copulation, where males compete for who’s sperm is used to fertilize the female’s eggs

What are the four types of sperm competition

Prolonged copulation, Displacing previous males sperm, Mating plugs, Male secretions

Described prolonged copulation as a sperm competition strategy

When the male stays with the female post copulation for hours to days (AKA Mate guarding)

Describe male secretions in terms of sperm competition

Males can secrete an anti-aprodisiac that prevents other males from being attracted to the affected female

Describe sperm competition in Odonata

Males will scoop out previous male’s sperm (they have spikes on the adeagus that can also inflate to push out other sperm). This order also displays mate guarding, where in the copulatory position the female can literally not escape

Describe sperm competition in Cabbage White Butterflies

Males compete for sunspots, once they have courted the male will cover the sperm in a hard coating that will take days to breakdown in the females. This lead to the evolution of teeth in the female’s vaginas to assist in the breakdown of the sperm package

What is cryptic female choice

Females choosing males after copulation, based on the sperm she already has

Describe the key features of insect eggs

There is the atrial opening that allows sperm fertilization, and a variety of layers that offer different levels of protection

What is Parthenogenesis

Development from an unfertilized egg

What stimuli are important to insects?

Mechanical, Electromagnetic, Chemical

What are trichoid sensillum

External, hair-like sense organs that move in response to certain mechanical stimuli such as touch, body movements, sound, vibration, gravity, and wind

What are the main components of the Trichoid Sensillum

Tormogen cell (makes the socket), Trichogen cell (makes the hair-like structure), Dendrite of sensory neuron (stretches when trichoid sensillum moves and sends signal)

Describe Proprioceptors/”Hair Plates”

A group of trichoid sensillum near joints that are stimulated with the join is bent which then provides information on how the insect is moving. Can also be indicative of wind and flight speed

What are 2 examples of Trichoid Sensilla being used

1) Monarch caterpillars have trichoid sensilla that can detect certain frequencies and signal the central nervous system, the response is the caterpillar flicking its body as a warning or defense mechanism (used to detect wasps and other predators)

2) Crickets and cockroaches have trichoid sensilla on their cerci which can detect even the smallest air movements (this makes them very good at scrambling away from predators as they approach)

What are campaniform sensillum

Stress receptors (class of mechanoreceptors) that are typically located on joints of legs and wings. Differ from trichoid sensillum as they are a dome structure rather than hair structure like trichoid sensillum. They monitor movement of wings during flight

What is a scolopidum

Unit of a mechanoreceptor organ in insects comprised of three cells, commonly located in the antennae and serves a function in insect ears

What is the chordotonal organ

A sense organ that is comprised of many scolopidia

What are some functions that the chordotonal organ assists with

1) Near field hearing in mosquitos

2) Tympanal hearing in crickets

What is electromagnetic stimuli

Sensing visible, ultraviolet, and infrared light

What are the three photoreceptors

Dermal receptors, Stemmata, and Ocelli

What are Dermal Receptors

Free nerve endings in the brain that are used to detect light (no focusing structures)

Describe the form and function of Stemmata

A little more advanced, can form a crude image by gathering light from surroundings. Consist of corneal lens, rhabdom (contains pigments) and the retinula cell (sensory cells). Stemmata are the only visual organs found in holometabolous larvae

Describe the function of ocelli

They function as horizon detectors to facilitate diurnal rhythms

Describe Compound Eyes

Compound eyes are found in many adult insects, they are composed of hundreds of smaller structures called ommatidium

Describe the form of Ommatidia

Ommatidia have a corneal lens that focuses the light that is connected to a rhabdom (pigment cell) and retinula cell (sensory cell)

What is Photopic/Apposition eye

The image produced is a collection of points from each ommatidium individually. This is found in diurnal insects as there is a lot of light during the day

What is are scotopic/superposition eyes

Light can pass through multiple ommatidium and they work together to focus light and form an image. This is found in nocturnal and crepuscular insects such as moths and beetles

What are the two main genera that have IR sensilla

Melanophila and Aradus

How do thermoreceptors work

in Genus Melanophila, the Infrared Sensilla can detect very small changes in heat which causes expansion of the fluid core of the receptors. This expansion is than turned into a signal to the mechanosensory dendrite

What is the function of chemical stimuli

Chemical stimuli helps insects find food, triggers the laying of eggs, helps them find a mate (pheromones), and can sense CO2

What are the two types of chemical sensory organs

Olfactory Sensilum, and Gustatory Sensillum

Describe the Olfactory Sensillum

These receptors are thin-walled and detect air-borne scents. They produce Odorant Binding Proteins (OBP) and volatile compounds can diffuse through the thin wall

Describe gustatory sensillum

These receptors are thick walled with only one pore on the end which is used to taste sugars and salts in liquid

What are the three levels of insect defense

Avoiding detection, avoiding attack, and avoiding consumption

What are the four strategies used for avoiding detection

Camouflage, Masquerade (mimesis), Disruptive colouration, Countershading

Describe camouflage

Matching the general background

Describe Masquerade/Mimesis

Resembling a specific object in the background (ex. inchworm mimicking a twig). Predators might see the insect, but they don’t recognize it

Describe counter shading

Ventral part is darker to even out colour as light shines on it from above in the Saturniidae caterpillar

Describe disruptive colouration

A drastic contrast in colour that breaks the outline so predators don’t understand where the prey is

What are the strategies used to avoid attack and consumption?

Thanatosis, Startle behaviour (Deimatic display), Chemical weapons, Aposematism, Mimicry

Describe thanatosis

Pretending to be dead, many predators don’t want to eat something that has been dead a while

Describe Startle/Deimatic display

Sudden movements, sounds, or eyespots that may scare away predators, usually found in species that are not very common

Describe the chemical weapons insects can use as defense

Some insects have specialized chambers, spines, have particular gut contents, or can reflexively bleed certain chemicals. This is typically very energetically costly for insects to make. (ex. Bombardier beetle that has a reservoir and reaction chamber that is able to synthesize and spray hot acid)

Describe Aposematism

Conspicuous signals, like bright colours, or sounds to warn predators that an animal is dangerous, toxic, or unpalatable

What are the two types of mimicry

1) Batesian: when something that is not toxic mimics something that is toxic and therefore gains protection from mimic

2) Mullerian: When toxic animals adopt similar colouration to display widely known toxicity

What are the level of sociality in insects

Solitary, Subsocial, and Eusocial