Entomology Exam 1

entomology

the study of insects

can be done by professionals and everyday citizens

importance of insects

insects are important to ecology

nutrient recycling (fall in between macro and microscopic levels of the world—breakdown micrbes)

plant propagation (pollinators are key for 70% of food supply)

maintenance of plant community, food source (humans and other animals), maintenance of animal community (help to manage both plant and animal populations)

keystone species

vital to entire ecosystems (thought of as most important)

insects are one

biodiversity of insects

dominate in numbers and volume

1.0+ million species

span 32 orders but 5 dominate (coleoptera, lepidoptera, hymenoptera, diptera, hemiptera)

species richness come from extrapolations (how many are found per year)

reasons for insect species richness

highly organized sensory and nervous system (fires repeatedly to different ganglia to operate different things, not logical but can react quickly to environmental stimuli)

short life periods (quick generation times—100s per brood, multiple broods per year)

sexual selection and adaptation (propensity for isolation—driven by distance to result in different species)

metamorphosis (insects at different life stages don’t compete with one another)

wings (shape and position determines ecologial role)

miniaturization (allows them to fit in smaller places, use less oxygen)

feeding group diversity

mining (eat a tunnel through a leaf-safe from predators while eating)

netting (avoids tertiary veins)

chewers

different eating patterns allow multiple types of insects to use the same food source

hierarchy of biological classification

species (most specific)

genus

family

order

class

phylum

kingdom (least specific)

exoskeleton

insects have no internal skeleton

a hard outer covering made of chitin that supports body shape and protects internal organs

this must be shed through molting throughout an insect’s life to grow and develop

apodemes

projections into the inside of the insect where muscles attach to exoskeleton

suture

an incision-like indentation in the exoskeleton to allow for more flexibility

ecdysial line

where molting starts

a pre-formed, weakened area in an insect’s or arthropod’s rigid outer shell

allows insect to more easily split its exoskeleton at the end of a molt

spine

an immobile projection from the exoskeleton that is like a thorn

spur

a projection from the exoskeleton that an insect can move by flexing

seta

a projection from the exoskeleton that act as sensory hairs

basement membrane

everything in exoskeleton is ultimately anchored to this

basal part of body walls formed from degenerated epidermal cells

made of fibrous protein, collagen, and glycoproteins

forms a continuous sheet beneath the epidermis, where muscles are attached

epidermis

under the cuticle but above the basement membrane

unicellular continuous layer formed from polygonal cells (modifies into cuboidal or columnar during molting process)

adjacent epidermal cells are held together by desmosomes (like rivots holding the cells together)

all the cells are glandular and secrete either the cuticle or the enzymes involved in the production and digestion of the old cuticle (anything broken down gets reused)

absorb the digestion products of the old cuticle and repair the wound

cuticle

the part that is actually shed

contains the epicuticle, exocuticle, and endocuticle

is the secretory product of the epidermis

determines the surface pattern and physio-chemical properties of integument

divided into 2 regions: upper epicuticle and inner procuticle (exocuticle and endocuticle)

contains proteins (arthropodin, sclerotin, resilin)

epicuticle

outermost, thinnest layer

made of protein and sugars

1-2 cells thick

cement layer (top), wax layer, polyphenol layer, cuticulin layer,

exocuticle

middle layer

thicker

made of chitin and proteins

proteins are tanned by phenolic substances to produce sclerotin, giving rigidity to cuticle

endocuticle

made of fibrous chitin towards top and unhardened proteins towards the bottom to allow for movement of substances

thickest bottom layer

proteins are not tanned

soft and flexible (not sclerotized, mostly made of arthropodin)

procuticle

term for the endocuticle and exocuticle together

Tormogen cell

cells that are wrapped around the hair shaft

non-sensory cells

secretions are to protect the trichogen cell

Trichogen cell

the cell with the hair bulb

secretes setae

endocrine gland cell

create hormones and neural transmitters that stay inside the insect

exocrine gland cell

create hormones that exit the cuticle

chitin

a polymer only found in crustaceans, insects, and some fungi

second most abundant biopolymer

results in a hardening

made of glucosamine monomers and N-acetyl groups

adjacent chains held together by beta-glycosidic linkages

is insoluble in water, alcohol, organic solvents

is soluble in concentrated mineral acids and sodium hypochlorite (why pesticides have to be so strong)

synthesized by the insect epidermis

sclerotization

the hardening of the exocuticle

like tanning leather (eventually gets hard and brown)

cuticular perturbances

multicellular spine

acanthae

seta

microtrichia

multicellular spine

large and bulky spines that protrude

made of the cuticle and epidermal cells

seta

not a cell but a secretion from a trichogen cell

a sensory hair that protrudes out of the cuticle

microtrichia

tiny little sensory hairs

acanthae

microscopic secretions to increase surface area of cuticle

segmentation

insects are made of repeating body segments

can be primary, secondary (non-winged), or secondary (winged)

primary segmentation

found in some soft-bodied insect larvae or other primitive forms

no hardening visible over joints (ex. caterpillars) and boundaries between segments are marked by simple infoldings of the body wall

secondary segmentation (non-winged)

hard body plates over “joints” with flexible intersegmental regions to allow for movement and flexibility

secondary segmentation (winged)

wings need to move with greater flexibility than legs

no sclerites around wings

tagmatization

specialization of segments over time to perform distinct and independent functions

head, thorax, abdomen

head

specialized for feeding and sensory input (eyes, antennae)

thorax

specialized for locomotion (legs and wings)

abdomen

handles visceral, reproductive, and respiratory functions

dorsal

top of the insect

where the wings come out (if winged)

ventral

bottom of the insect

where the legs come out

posterior

back of insect

butt

anterior

front of insect

head

proximal

closer to the body

dorsal

farther from the body

median line/medial

in the middle

lateral

towards the side

head segments

6 fused segments (preantennal (ocular), antennal, labral, mandibular, maxillary, and labial)

2 functional units (cephalic sensory and mouthparts)

ocellus (ocelli)

very simple eyes that only detect light

frons

forehead (really looks like it’s in the middle of the face though)

gena

“cheeks”

lateral parts of the head, under the compound eyes

labrum

upper lip

mandibles

hold the teeth used to crush

maxillae

more like typical teeth

have sensory projections attached

labium

like the chin

have sensory projections attached

all insects will have the same ____ but they are adapted

mouthparts

ex. difference in fly and mosquito feeding

insect vision

consists of compound eyes and ocelli

compound eye

many lenses (stemmata) put together

antennomeres

segments on antennae

scape

first segment of antenna that attached to head

pedicel

second segment of antenna

flagellum

the rest of the antenna

flagellomeres

segments of the flagellum

Johnston’s organ

helps insects during flight to fix their speed and orientation

Sensilla (arista or style)

extra sensory organs at the end of the antenna

thorax

middle region of insect body

all 6 legs and wings (if applicable) are connected to the thorax

coxa

attaches leg to the thorax

like a hip

trochanter

connects coxa to femur

femur

large upper bone of insect leg

think human femur

tibia

smaller middle bone of insect leg

tarsus

insect “foot”

has tarsal claws (kind of like toes)

tarsomeres

parts of tarsus

significant leg adaptations

roaches-long legs to run fast and keep body high off of ground

mantids-2 raptoral legs to grab prey

diving beetles-hairs off of legs to hold onto oxygen while diving

lice and mites-claws to grab onto hairs

closed cell (wings)

a cell is completely surrounded and enclosed on all sides by veins, It does not touch the outer margin of the wing

open cells (wings)

a cell is missing a vein on at least one side, meaning its outer boundary runs right into the open edge (margin) of the wing

dermaptera wing folding

have to pull a covering off to get their wings out

insect flight adaptations

coleoptera- all fold wings under a hard shell (elytra)

Diptera-usually have 2 wings instead of 4 and have hauteres instead

Thysanoptera-wings undulate

Hymenoptera-forewings and hindwings look attached, but are not

ovipositor adaptations

insects’ ovipositors are modified based on where they like to lay their eggs

ex. grasshoppers have a shovel-like ovipositor because they like to lay their eggs underground

cerci

paired appendages found on the rear end of the abdomen

can be very small or very large

can be strictly for sensing or can serve other purposes (pincers on earwigs)

hemocoel

the primary body cavity in animals with an open circulatory system where blood directly bathes the internal organs

hemolymph

circulatory fluid that combines the functions of blood and lymph

all organs sit in this (surrounded by it)

trachaea

tiny tube-like channels used to breath

oxygen goes directly to body tissues

spiracles

little valves that connect tracheae to exoskeleton and let in oxygen while preventing water loss

Malpighian tubules

slender tubes that connect the midgut and the hindgut

waste is pumped into them so that additional nutrients can be extracted and absorbed into the body

actual waste is sent back to the hindgut to be excreted

muscles and locomotion

only have striated muscles

hydrostatic skeleton

if larval body is pierced, everything just comes out “pops”

synchronous vs. asynchronous movement

synchronous- 1 signal, 1 movement

asynchronous- 1 signal, many movements (like a cascade)

hydrostatic skeleton

“turgor” muscles continually contract and hemolymph puts pressure to keep shape (larvae)

apodous larvae movement

contractile waves of entire body (head to tail)

terrestrial larvae movement

use hooks

aquatic larvae

anterior-posterior (head to butt) waves form undulating motion (like dolphin kick)

larvae with thoracic legs and abdominal prolegs

posterior-to-anterior waves

up to 3 waves simultaneously

ex. caterpillars

adults with hard exoskeletons

use antagonistic and agonistic contractions

(1 muscle contracts, another relaxes)

only have 3 legs touching a surface when in motion (front and back leg on same side move with middle leg on opposite side)

flight muscles

slower flyers maintain wing beats by synchronous muscles

fast flyers maintain wing beats by asynchronous muscles

nervous system

over evolutionary time, insects have developed fused ganglia which allows for signals to send very fast (less distance to travel)

older orders of insects have more spread out ganglia while more recently diverged orders have ganglia closer together or fused

ecdysone

begins the molting process in nymphs and adults

juvenile hormone

when present in high amounts, less development happens

produced in the corpora allata (part of brain stem) and inhibits genes that promote development (keeps them “immature”)

corpora allata shrinks during last larval or nymphal instar (stops production of JH and causes insect to molt into an adult (if hemimetabolous) or a pupa (if holometabolous))

outcome of a molt determined by the level of JH in holometabolous insects, all or nothing in hemimetabolous insects (large JH= larva to larva, small JH=larva to pupa, no JH= pupa to adult)

Inka cells (pre-ecdysis hormone)

release a hormone to tell the system to start producing ecdysone

circulatory system

open system

6 chamber heart

blood cycles through heart and out the aorta

blood is then in hemolymph

hematocyte functions

phagocytosis (immune cells engulf foreign microbes)

encapsulation of parasites

coagulation (can clot the hemolymph so wounds heal during the next molt)

storage/distribution of nutrients (move nutrients around)

no red/white blood cells like humans—all 1 cell