BIOL 327 TERMS

Frons

the front of face

gena

the side of the cheek

occiput

back of the head

vertex

front of the head (not frons)

antenna

a pair of long, thin sensory appendages on the front of the face

labrum

upper lip

mandible

teeth, can be modified to chew (bees and beetles) ,

maxilla

mouthpart behind the mandible used for tasting food, can be fused with labium to form a proboscis (bees and butterflies and cicadas)

maxillary palps

sensory organ on the maxilla used in tasting food

hypopharynx

tongue of insect, can be modified to sponge fluids, or in mosquitos, drips anticoagulant.

labium

bottom lip of insect, can be fused to form a proboscis or in mosquitos, a straw to suck the blood out.

labial palps

sensory organ found on the labium

head capsule

6 segments fused at birth to form the head of the insect (not sclerotized)

consists of (labral, antennal, post-antennal, mandibular, maxillary, labial)

integument

outer layer of an insect, consisting of cuticle and epidermis

suture

line/groove where there is a union of 2 sclerites or plates, line of weakness across a sclerite

sulcus

a line marking an internal ridge or cuticle

hypognathous

downward facing mouthparts (orthoptera)

prognathous

forward facing mouthparts (coleoptera beetles)

opisghognathous

rear-facing mouthparts (hemiptera)

thorax

where the wings and legs of an insect are attached

pronotum

top surface of the prothorax that usually acts as a shield

prothorax

first segment of the thorax, contains the pronotum and a pair of legs

mesathorax

second segment of the thorax, contains a pair of wings and legs

metathorax

last segment of the thorax, contains a pair of wings and legs

femur

largest segment of insect leg (the thigh)

coxa

attaches leg to thorax, first segment of insect leg

trochanter

second segment of insect leg, acts like s joint to move the leg

tibia

leg part below femur, contains tibial spurs

tibial spurs

a bony projection originating from the tibia

tarsus

multiple segments that from the toes of the insect

pleural sulcus.

line between the tegnum and the pleura

tegnum

top surface of abdomen

sternum

bottom surface of insect abdomen

pleura

middle of tegnum and sternum

ovipositor

egg laying organ for female insects

abdomen

usually has 11 segments on the top and 8 on the bottom of the insect. Contains organs of insect. pregenital segments are segment 1-7 on the tegnum, 8-9 form the external genitalia and 10 and 11 form the cercus

lek behavior

a territorial behavior in which male insects compete for female attention. Female insects visit the lek to choose a partner for mating

visual displays

some insects perform visual displays to attract mates, eg.) butterfly dance, firefly emissions

chemical attractant

some insects attract mates over long distances using pheromones that can travel past 1km

sound production

some orthoptera have special structures that allow for stridulation and produce noises to attract mates

courtship

when insects attract mates through visual, chemical and auditory signals for copulation(mating)

copulation

mating, this can be done through tactile stimulation, short range chemical stimulation and is often complex

post-copulatory behaviors

prevents females from accepting other males. dragonflies guard female through tandem flight. 

Moths secrete fluid to block females from receiving other males and stop females from releasing sex attractant.

some males produce genital plug to prevent females from mating with other males.

fertilization

primitive insects indirectly transfer sperm through a spermatophore (sperm package).

mating is internal with higher orders of insects, sperm is maintained in females spermatheca (sperm pouch)

blastoderm

an early stage where only nuclei divide to form the walls surrounding the yolk.

germ band

a region on the blastoderm which stretches to form the segmented trunk of the insect

endoderm

a layer of the developing germ. develops into the lining of the digestive system, which is a major internal structure of the insect.

mesoderm

the middle layer of the developing germ, develops into the circulatory system muscles and exoskeleton, lateral oviduct and vas deferens

ectoderm

the outer layer of the developing germ, develops into the epidermis (outer protective layer of skin), the brain, spinal cord, nerves, and the respiratory (tracheal) system.

ametabolous

only difference between immature adults is size and development of gonads

hemimetabolous

gradual change through several instars, external wing development, immature insects referred to as nymphs, aquatic specise as naiads

holometabolous

internal wing development. fermentation of pupa. maturation of wings, external genitalia and adult structures. immatures referred to as larvae

viviparous

give birth to live young

oviparous

give birth to egg

homeostasis

a constant internal state required for the proper functioning of cells

malphigian tubules

secretes sugar, amino acids water kcl, toxins and nitrogenous wastes

primary urine emptys into hindgut for ressorptions

water resorption in rectum for water balance in the insect

main excretory organs

blind-ended tubules

lined by a single layer of epithelial cells

3 cells

number of tubules 2-250

low excretion of primary urine

minimal energy expenditure

removes nitrogenous waste and uric acid

MNSC

direutic hormone

allows insect to urinate

triggered by gut distension

antidiuretic hormone

prevents water loss

reabsorbs fluid from hindgut

mealworm execretory system

they live in a dry environment

powder-dry poop → cryponephridium

eats dry food

all h20 is absorbed

desert locust execretory system

eats succulents

moist poop

w/o food or h20 has moist excreta

blood feeders

feast or famine

takes meal 10-20x body weight

excretes 50% of ingested flood within hours

concentrates red blood cells in gut

excretion rate increases 100 fold within a few minutes

execretory process

eliminate most blood solutes non-selectively in malphigian tubules

selectively resorbs useful solutes in hind-gut

actively excrete certain toxins through malpighian tubules

controlled by 2 hormones diuretic and antidiuretic

insects often have low blood pressure with dehydration not being detrimental

most insects urinate kcl

large concentration gradient between hemplymph and mt lumen

diffusion of all other blood solutes

regulation of food intake

insects regulate food intake through 

external stimuli - olfaction, gustation, vision (smell,taste,shape of food)

internal stimuli -crop volume and nutrient concentrations in hemolymph

volume detected in foregut

some digestion may occur as a result of saliva → foregut distended and insect wont eat until full digestion occurs in midgut

other factors- state of hunger

nutritional state and non-associative learning

all food goes to the subesophageal ganglion

food intake process

3 stages → biting continuation termination

temperature has negative effect on feeding

wide variety of eating behavior due to variation in mouth parts

som chemicals in food can be phagostimulants => stimulate feeding

phagodeterents → inhibits feeding even in presence of stimulants

sensory input from deterrents outweight stimulant input 8 to 1

monophagous

feeds on 1 plant family

few sensory receptors

considered more advanced than polyphagous insects because they can choose

polyphagous

feeds on multiple plant families

oliphagous

feeds on a few plant families

biting

initiation of feeding

detects stimulus from food

phagostimulantt as percieved by sensilla

(doesnt have to be on the mouth)

blowfly biting example

stimulation of tarsal sensilla

extension of proboscis

continuation → sensilla on labellum and feeding proceeds

schistocerca biting example

initiation

Tarsal, maxillary, and labial palp sensilla all need to be stimulated to initiate biting

continuation: after the first bite, quality of food is monitored by cibarial receptors

termination of feeding

decay of excitatory state

chemosensory adaptation/ habitation

increased foregut volume

negative feedback

nutrients

hormonal factors → hemolymph

salivary glands

piercing, sucking mouthparts

saliva of blood feeders  → most dangerous period for insect

made of local anaesthetics, vasodilators and anticoagulants

saliva of sucking plant feeders, Hemiptera

digestive enzymes → amylase, invertase, proteases, lipases

aphid saliva → pectases

facilitates penetration of stylets

digestion

enzyme secretion in the midgut

secretion regulated by → secretagogue, neural stimulation and hormonal stimulation

The rate of digestion is often determined by the rate of polysaccharide breakdown to monosaccharides.

microbial endosymbiosis

Many insects require microbial symbionts for adequate nutrition

transferred on eggshells

sequestered cellulases from fungi

Lower termites obtain cellulase activity from enteric protozoa and bacteria

thrive in the anaerobic region of the hindgut called the paunch

insect nutriton

insects require

10 essential amino acids

phenylalanine

important for larval growth

cyclitols

myo inositol

Vitamins A B C

free fatty acids + sterols