Entomology Lecture

8/3/2019 Entomology Lecture

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Entomology is the

Study of Insects


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Insects are the most diverse and abundant formsof life on earth.

There are over a million described species-

more than 2/3 of all known organisms There is more total biomass of insects than ofhumans.

Insects undergo either incomplete or completemetamorphosis (Egg to larva to pupa to insect)

Larva have a soft tubular body and look likeworms. Fly species larvae are maggots


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A single insect bears 3 pairs of legs, 2 pairs of wings,compound and simple eyes, and 2 antennae.

The insect exoskeleton provides tremendous strength ...

Insects are upside-down ... they have a dorsal heart and aventral nerve cord.

The insect respiratory system is comprised of holes(spiracles) in the abdomen and thorax, and tubes(tracheae) that allow outside air to reach locations next tobody organs.

Insects smell with antennae and taste with tarsal (foot)

pads (and other organs). Their phenomenal features include stalked eyes, brightly

colored hairs and spines, large horns, powerful jaws, andovipositors adapted for spectacular uses.


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Respiratory system (tracheal system):Spiracles: External openings on each

side of most body segmentsTracheae: large tubes that run the length

of the body on each side. Smaller tubesare called tracheal branches and

tracheoles.Air sacs that store air (air, not just

oxygen) may be located in the abdomen

and/or the thorax.


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Most insects are oviparous females lay eggs. The

act of egg-laying is called oviposition. Eggs may be laid singly or in masses; often they are

coated with a sticky substance secreted fromthe female accessory gland to glue them to each otherand a plant surface (or other substrate). Inmost insect groups, eggs are laid shortly afterfertilization; egg development does not occur in

the mother.


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Exceptions to the general rule include: Ovovivipary: Eggs are incubated in the female until nearly ready to

hatch, and hatching occurs almost immediately after oviposition; thisoccurs in some cockroaches, aphids,scales, beetles, thrips, and flies(but is not the rule in any of these groups).

Pseudoplacental vivipary: Egg develops in maternal tissue where

nutrients aretransferred to the developing embryo; offspring is born

immediately upon hatchingfrom the egg. Common in many aphids;also occurs in some earwigs, Psocoptera, Nad, one family ofHemiptera.

In a few fly families, larval development occurs entirely within themother, and the fully grown larva pupates immediately after birth.

This occurs in the tsetse fly, the louseflies or keds, and the bat flies.


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Sperm storage in the spermathecaallows females to store sperm tofertilize eggs later, in the absence ofmales (sperm remain viable in thespermatheca of queen honey bees for upto 3 years).


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Parthenogenesis: Reproduction viadevelopment of unfertilized eggs

Eggs may be all female (thelytokous

parthenogenesis) aphids Eggs may be all male (arhenotokous

parthenogenesis) many Hymenoptera

Polyembryony: Two or more embyosdevelop from one egg; common inHymenoptera.


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Pupae of a Hymenopteran parasite on a hornworm, Manduca sp.An adult wasp inserted one egg into this larva, and multiple

embryos developed. Larvae of the wasp fed inside the hornwormand have exited the body and spun cocoons in which they have

pupated.


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Most insects are diploid, with one set ofchromosomes from each parent. XXindividuals usually are female; XO aremale.

Haploid diploid sex determinationoccurs when unfertilized eggs develop into

haploid individuals and are male; fertilizedeggs develop into diploid females

occurs in Hymenoptera.


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Thoracic tympanae of moths ... for avoiding bats /sometimes they aid in attracting bats

Stridulation ... the sound-producing process ofcrickets

Compound eyes ... 30,000 facets in one compoundeye in a dragonfly ... they sense movement andsome color, but provide poor resolution.

Bioluminescence ... In fireflies, flying males flashfirst; stationary females respond by flashing back.

If the flash intervals are correct, the male flies tosource to mate.


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Phylum (and subphylum)Class (and subclass)Order (and suborder)SuperfamilyFamily (and subfamily)(Tribe)

Genus (and subgenus)Species (and subspecies)

Entomology Lecture

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