Basic Entomology
By: Bob Gara

Overall Goal
The Insect Orders: You
Should Know Them
When You See ‘Em
Hi, Bob, it’s a beetle!

Remember the Phylum Arthropoda: even spiders are arthropods
1. Jointed appendages
2. Body composed of somites
3. Exoskeleton
4. Dorsal heart
5. Ventral nervous system

All are arthropod classes
Sea-spiders
Horseshoe crabs
Mites
Ticks
Pycnogonida
Merostomata
Arachnida
Arachnida
Millipedes
Centipedes
Many other classes too
Diplopoda
Chilopoda

The insects belong to the Class, Insecta

Insects: The class Insecta
• Three body regions
- head
- thorax
- abdomen
• One pr. antennae
• Adults; winged
• Three pr. legs

Besides these basic insectan characteristics, I’m going to discuss: molting, metamorphosis, the mouth, the wings, the digestive system, and other stuff.

1 st , a new word: “molting” shedding old exoskeleton
2 nd , a new word: “instar” the insect between molts.
(1) molting
Egg
(2) instars of the Psylla
3rd
Adult
1st
2nd
4th

Since all arthropods, including the insects, have a hard exoskeleton they have to change it in order to grow. This process is called MOLTING.
Cicada molting

This is molting

Metamorphosis – “change in form”
No metamorphosis
Incomplete metamorphosis

The silver fish: order, Thysanura , has no metamorphosis.
Common silverfish
Jumping bristletail
(found in the forest)

Mayflies (order Ephemeroptera) have incomplete metamorphosis

Gradual metamorphosis
Complete metamorphosis
The Pupa

The plant hoppers, order
Hemiptera, has gradual metamorphosis.

Complete Metamorphosis!!
Eggs Maggot The pupa! Adult
Some terms associated with complete metamorphosis
Egg Larva Pupa Adult reprod.
Function beginning feeding reconstruction growing transformation
Character- inactive active inactive istics helpless
Other names nit grub chrysalis maggot puparium caterpillar cocoon active no growth!
imago

Grasshopper, order: Orthoptera
Chewing mouthparts

Mouth ocelli antennae compound eyes clypeus labrum mandible peeking out palps

Labrum
Palp
Some dentistry
Maxilla
Tongue
Palp
Labium
Mandible

Again, the chewing mouth parts
Labrum
Palps
Mandible
Maxilla

Look at the variations found in the
parts
Fierce predators: Tiger beetles

Adult
Another fierce predator: Dragon flies
Nymph

Adult
Calculates: speed and direction of the prey

Mouth parts: Piercing-sucking
(order Hemiptera – the bugs)

Piercing-sucking mouth parts of the Hemiptera
Maxilla
Mandible

More detail of piercing-sucking mouth parts of the
Hemiptera

More, piercing-sucking mode of feeding.

What’s so great about having
6 legs?
Legs on ground
Legs off ground
Insect legs

Digestion in insects
Guts of a larva

• Digestion
• Circulation
• Nervous system

Ok, enough already, tell ‘em about the insect
Orders!

Within the class Insecta there are about 20 insect orders.
Of these 20 I’ll introduce you to a few of them – of these few,
will identify 5 of them:
1. Hemiptera – the bugs
2. Coleoptera – the beetles
3. Lepidoptera – the moths and butterflies
4. Hymenoptera – the wasps, ants and sawflies and horntails
5. Diptera – the flies

Collembola: the springtails.
• Variable in form, wingless, no metamorphosis, chewing mouthparts
• Have a “glue pot” on 1 st abdominal segment
• Have a jumping organ, furcula
• Furcula held down by a latch called a tenaculum
• The word “cola” is Latin for glue
Gluepot

Collembolans are important!
• live in the forest litter
• 1 st step in decomposition
• operate:
- chip-up leaf particles
- increases surface area
- greater feeding ground for fungi and bacteria
- mix organic particles into mineral soil
- fecal matter adds to soil fertility
Some studies:
• 7% of ingested litter matter was ingested, 93% egested as fecal pellets;
• fecal pellets: increase surface area, aeration, pH, water holding capacity;
• in 9 months, 60% of litter processed by earthworms, mites etc.; the rest by collembolans

Thysanura: the silverfish, fire brats & bristle tails
• no metamorphosis, chewing mouthparts
• no wings, scales on body, 3-tails, fast movements
• skinny legs – fast!
• Importance:
- domesticated
- live under baseboards, stoves, sinks, cabinets, books etc.
• huge pest in libraries
• family Machilidae live in litter with collembolans and important in mineral cycling

Here’s some trivia that only entomologists could love:
• fossil insect
• all insects have these muscles
• flight
• contraction of these muscles allows for wing movement
& flight

The Ephemeroptera (mayflies) and the Odonata
(dragonflies & damselflies) are ancient remnants of the earliest flying insects.
When not flying mayflies and dragonflies can’t fold their wings. They either hold them “tent-like” over their thorax or out horizontally. The wing-folding mechanisms wasn’t invented yet: the axillary sclerites.
These are axillary sclerites that allow for wing folding – most insects have these mechanisms.

Ephemeroptera * : the mayflies
• ± 2,000 spp.
• 2-pr. membranous wings held tent-like over body; gills
• adults have no mouths, incomplete metamorphosis;
• aquatic immatures;
• 1 ° consumer role in the aquatic ecosystem.
* ptera- Gr. for wing ephemera- Gr. prefix for temporary

Ecological role of mayflies:
• shredders – headwaters of streams;
• scrapers – scrape off 1° production on stones and boulders
• collectors – collect fine particles as they drift down stream;
• filter feeders – strain microscop ic particles from the water column;
• predators – few immatures are predators

Odonata: dragon flies and damsel flies:
• adults and nymphs exquisite predators!
• two pr. wings held horizontal by dragonflies and tentlike by damsel flies (but can’t fold them);
• chewing mouthparts, incomplete metamorphosis;
• adults are territorial and capture prey in flight;
• ecological pts.
- prey for birds
- movement of energy from aquatic to terrestrial ecosystem
- increase energy flux within aquatic ecosystem ( role as general predators)

All the rest of the insect orders have wing folding and let’s first talk about the Orthoptera.
Orthoptera: grasshoppers, roaches, mantids, crickets, katydids, etc.
• have chewing mouthparts, and 2pr. of wings either held straight back, like the grasshoppers, or flat along the top of their bodies;
• gradual metamorphosis
• most phytophagous, but some are predacious like the mantids

Dermaptera: earwigs
• Chewing mouth parts;
• 2pr. wings, 1 st pair truncate and hardened;
• gradual metamorphosis
• posterior – a pincher
• can be pests of nurseries

Isoptera: termites:
• have a caste system, live in colonies;
• typically have, sterile workers, soldiers and reproductives;
• have yearly swarms of males and females to establish new colonies;
• in the PNW establish colonies in wood, paper piles – houses;
• order characteristics:
- 2pr. wings of equal length
- chewing mouthparts
- gradual metamorphosis

queen steriles reproductives
Queen regulates and controls the castes through a process of tropholaxis

Termites continued:
• ecological benefits:
- increase surface area of large woody material;
- great amount of fecal matter enriches the soil;
- main agent of soil turnover in tropics: earthworms in the temperate parts of the world.

The Hemiptera: bugs, leaf hoppers, aphids, scales, toe-nippers, assassin bugs, white flies, tree hoppers etc.

When I was a student of entomology: two discrete orders
Hemiptera = gr. half wing wings the same
Homoptera = wings all membranous

Then it all changed: China went to
Chile.
• Now, the “old Hemiptera and
Homoptera” are lumped into the new order, Hemiptera.
• What used to be the Hemiptera is now called the suborder,
Heteroptera.
• What used to be the Homoptera is now called the suborder,
Homoptera.

So, the order Hemiptera has these two suborders.
(1) Heteroptera: the bugs:
• gradual metamorphosis, piercing-sucking mouthparts;
• two pr. wings – upper part hardened, lower part membranous;
• bugs are phytophagous and predacious
• bugs are terrestrial, many aquatic hemelytra

Some Heteroptera

(2) Homoptera: aphids, scales, plant hoppers, cicadas etc.
• two pr. homogenously membranous wings (when winged);
• gradual metamorphosis (sometimes real weird) and piercing-sucking mouthparts.
plant hoppers tree hoppers cicada

Aphids are major pests in forestry; especially in nursery management.
Many aphids cause galls.

The scale insects are terrible homopterans, especially in urban forestry

Coleoptera, the beetles:
• > 550,000 species
• complete metamorphosis
• chewing mouthparts
• 2pr. wings; front pair hardened and called an elytra.
Hind wings are membranous.

Even in the early beginnings of the profession of Economic Entomology, the beetles played a major role.