Entomology

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Entomology
Life Science & Study Event
Forum Threads 2015 2014
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Question Marathons 2014
Division B Champion Paul J. Gelinas Junior High School
Division C Champion Waynflete School

Entomology is an event in which competitors must be able to identify insects from 30 orders and 100 families. On most tests, questions about behavior, structure, human impact, and any characteristics of certain insects may be asked. This event is similar to the old Division B event, Don't Bug Me.

The 2015 Official Insect List is located on soinc.org.

Contents

What is an insect?

Before getting into the specifics of identifying insects you have to know what an insect is. An insect is an invertebrate with several distinguishing characteristics. These include: segmented bodies with paired, many jointed legs; 3 major body sections; 6 legs; and 2 antennae. After you have identified an organism as an insect you then must classify to its order and family. Note that color is generally not a good way to identify and differentiate insects. Some insects have specific patterns on their body that allow them to be identified. Think the Scarlet and Green Leafhoppers and their special red and green striped body.

Insect Taxonomy

All insects are classified as members of the following taxonomic groups:

  • Kingdom: Animalia
    • Phylum: Arthropoda
      • Subphylum: Mandibulata
        • Superclass: Hexapoda
          • Class: Insecta

This table outlines major characteristics members of each group are required to possess.

Insect Taxonomy
Level Name of Rank Characteristics Required
Kingdom Animalia Heterotrophic; Eukaryotic; Multicellular; No cell wall, no chloroplasts; Motile (able to move, opposite of sessile); Sense Organs.
Phylum Arthropoda Chitinous exoskeleton that must be shed during growth (molting); Jointed paired appendages (legs and antennae); Segmented bodies that are arranged into regions, called tagmata (e.g., head, thorax, abdomen); Bilateral symmetry; Ventral nervous system; Open, dorsal circulatory system;
Subphylum Mandibulata Have modified appendages (mandibles) flanking the mouth and used as jaws;
Superclass Hexapoda 3 pairs of legs (6 total) that are located on the thorax
Class Insecta Head, thorax, abdomen; 3 pairs of legs (one on each thoracic segment); One pair of antennae on head; 1-2 pairs of wings in most; Pair of compound eyes in most, along with 1-3 simple eyes;

Types of Metamorphosis

Not all insects develop in the same way. Types of metamorphosis are grouped based on the number of stages required to reach sexual maturity. The table below explains the different types of metamorphosis and gives example groups.

Types of Metamorphosis
Metamorphosis Type (alternate name) Description Wing Type Example Orders
Ametabola (no metamorphosis) Young resembles the adult, but is smaller. Development involves increasing the insect's size by going through successive molts. Apterogyte (adults like immature without wings) Protura, Diplura, Thysanura, and Collembola
Hemimetabola (incomplete metamorphosis) Developmental stages include egg, nymph, adult Exopterygote (wings develop externally on the nymph body) Emphemeroptera, Odonata, Blattodea, Mantodea, Isoptera, Grylloblattodea, Dermaptera, Plecoptera, Orthoptera, Phasmatodea, Psocoptera, Mallophaga, Anoplura, Thysanoptera, Hemiptera, Homoptera
Holometabola(complete metamorphosis) Developmental stages include egg, larva, pupa, adult Endopterygote (wings develop inside of body in immature insects and not visible until adult emerges from pupa) Megaloptera, Neuroptera, Coleoptera, Strepsiptera, Mecoptera, Siphonaptera, Diptera, Trichoptera, Lepidoptera, Hymenoptera

Insect External Anatomy

Head

The head is the anterior oval-shaped body region that that houses the brain, a mouth opening, mouthparts used for ingestion of food, and major sense organs (including antennae, compound eyes, and ocelli). The surface of the head is divided into regions (sclerites) by a pattern of shallow grooves (sutures).

  • Vertex: The uppermost sclerite (dorsal surface) of the head capsule
  • Coronal Suture: runs along the midline of the vertex and splits into two frontal sutures as it extends downward across the front of the head capsule
  • Frons: The triangular sclerite that lies between these frontal sutures
  • Epistomal Suture: A deep groove that separates the base of the frons from the clypeus
  • Clypeus: A rectangular sclerite on the lower front margin of the head capsule
  • Genae: Lateral sclerites that lie behind the frontal sutures on each side of the head

See [1] for more information and an interactive diagram of the head that includes all features listed above.

Eyes

Insects generally have two types of eyes, simple and compound eyes. Most have three simple eyes, also known as ocelli, located on the upper front part of the head. Several insects lack ocelli or only have two. Compound eyes are situated on the upper portion of an insects head and are composed of many facets, called ommatidia (singular- ommatidium). In some insects compound eyes occupy most of the head.

Antennae

The antennae are usually located on the front of the head below the simple eyes. These are great for identification. Some of the types of antennae include aristate (are pouch-like with a bristle), capitate (ends in a club), clavate (saw-like), filiformis (threadlike), geniculate (elbowed), monoliform (beaded), pectinate (comb-like), plumose (feather-like shape), serrate (sawtooth shape), and setaceous (bristlelike). See [2] for pictures.

Mouthparts

The mouth parts of an insect are located on the ventral or anterior part of the head. The mouth part structures typically present are the labrum (upper lip), jaw-like mandibles, jaw-like maxillae, a labium (lower lip), and the hypopharynx which acts as a tongue. Mouth parts are generally sucking or chewing. Insects with chewing mouth parts have lateral moving mandibles and chew their food, while insects with sucking mouth parts have parts like a beak which is called the proboscis through which liquid is sucked.

Diagram of head: Insecthead.gif

Thorax

This is the middle section of the body and is divided into 3 segments called the prothorax, mesothorax, and metathorax. Each segment bears a pair of legs, and the mesothorax and metathorax usually bear a pair of wings if the insect is not wingless. Each of the thoracic segments bear 4 groups of sclerites, or platelike areas. These are the notum (dorsally), pleuron (there's one on each side), and sternum (ventrally). These segments are then divided into even smaller segments.

The wings are located dorsolaterally (they're near the top) on the mesothroax and/or the metathorax. The muscles that move wings are attached to the walls of the thorax most of the time. Insect wings vary in number, size, shape, texture, venation, and in position held at rest making them a great assist in identification. Most insect wings are membranous, though some are thickened or leathery. Some are covered in hair and others in scales. Most insects fold their wings over the abdomen at rest, but others hold them vertically over the body or hold them outstretched. Here's a picture of wing venation:

General Venation

Insectwing.gif See bottom of http://www.cals.ncsu.edu/course/ent425/tutorial/wings.html for more.

Abdomen

The abdomen typically consists of 11 segments, but the last segment is usually represented by appendages only. Many insects have fewer abdominal segments because of fusing of some insects. Each abdominal segment generally contains 2 sclerites (or hardened body wall plate), a dorsal tergum and ventral sternum. The terga usually extend down the sides of most segments and overlap the sterna. Most insects lack appendages on the abdomen other than at the posterior end. This appendages may be lacking or drawn into the body and hidden. When these terminal appendages are present, they usually consist of a pair of cerci, a median dorsal epiproct (appendage above anus), a pair of paraprocts (pair of lobes located below and on each side of anus), and genitalia. The anal opening is on the posterior end of the abdomen, right under the epiproct. The sexes in many groups can be identified by the genitalia at the end of the abdomen.

Insect Identification (Orders Only)

For more detailed information about each taxon (both orders and families), please visit the Entomology/Entomology Insect List page.

Insect Identification
Order Name (nickname) Metamorphosis Characteristics
Protura (Telsontails) Simple conical head, piercing mouthparts, lacks eyes and wingless, 12 segments in abdomen, .6-1.5mm
Collembola (Springtails) Simple wingless, long bodies, 4-6 abdominal segments, multicolored, tube protrudes from abdomen, microscopic
Diplura (Diplurans) Simple 1-segmented tarsi, chewing mouthparts, 2 cerci on head
Thysanura (Bristletails,Silverfish) Simple spindle shaped, flat bodies with 3 long, bristly tail like appendages
Ephemeroptera (Mayflies) Simple distinguished easily by their two large, triangular wings
Odanata (Dragonflies & damselflies) Simple two pairs of elongate membranous wings, compound eyes large, abdomen long and slender, antennae very short
Plecoptera (Stoneflies) Simple 4 membranous wings, elongate, flattened, cerci present, long antennae, mouthparts chewing
Orthoptera (Grasshoppers & crickets) Simple usually 2 pairs of wings, antennae many-segmented, cerci present, has ovipositor, FW is long, narrow, and many veined
Blattodea (Roaches) Simple flattened oval bodies, long laid back antennae, wings (almost never used)
Isoptera (Termites) Simple small, soft-bodies, usually pale-colored, antennae generally short and thread- or bead-like
Dermaptera (Earwigs) Simple slender flattened bodies, large pincers at end
Mallophaga (Chewing lice) Simple bristly body, toothed mandibles, small compound eyes, abdomen more wide or as wide as head
Anoplura (Sucking lice) Simple flattened and wingless, sucking mouthparts, abdomen thiner than head
Thysanoptera (Thrips) Simple slender bodies, short antennae, short legs, feathery wings
Hemiptera (True bugs) Simple FW (front wing) thickened at base and membranous at tip, HW (hind) shorter than FW, wings held flat on body, tips of FW overlap, mouthparts sucking, antennae of 5 or fewer segments (long and conspicuous or short and concealed)
Homoptera (cicadas and more) Simple beak short and rising at back of head (different from Hemiptera), wings held rooflike over body, tarsi 1- to 3-segmented, antennae sometimes short and bristlike or sometimes long and threadlike
Neuroptera (dobsonflies, lacewings, antlions) Complete (finally) FW and HW almost same size, four membranous wings, wings held rooflike over body at rest, wings with many veins, antennae long, cerci absent, mouthparts chewing
Coleoptera (beetles) Complete FW horny or leathery, FWs meet in straight line on back, HW membranous and are usually longer than FW, wings rarely absent or reduced, antennae usually with 11 segments (sometimes with 8-10), antennae variable in form
Mecoptera (Scorpionflies) Complete slender, soft bodies; long legs and elongated, snout like heads
Trichoptera (Caddisflies) Complete shaped or colored like certain moths, antennae long and threadlike, antennae usually long as body or longer, HW a little shorter than FW
Lepidoptera (Moths & Butterflies) Complete 4 membranous wings, usually have proboscis in form of coiled tupe, wings covererd in scales
Diptera (True flies) Complete one pair of membranous wings (you can identify them instantly from this), have knoblike projections called haltares
Siphonaptera (Fleas) Complete laterally flattened abdomens, tough skin, enlarged coxae, mouthparts with 3 piercing stylets for blood sucking
Hymonoptera (Bees, Ants, Wasps, and more) Complete wings are sometimes present, FW a little larger than HW, antennae usually fairly long

Binder Checklist

*NOTE* The 2013-2014 competition only allows for one double-sided, 8.5 x 11 inches page of information. However, previous years have allowed for a binder, so it may still be helpful to create one for studying purposes.

Here is a binder checklist that was useful in the past: Make sure you have the following information in your binder or known by memory: Definitely necessary:

  • Insect identification guide and sheets
  • Nymph identification sheets
  • Insect pictures (obviously)
  • Insect characteristics sheets
  • Human impact information
  • Basic insect information

Optional:

  • Entomology glossary (to be on the safe side)
  • Note Sheets (for quick finding if they have a section where you must answer questions about insects not already identified) for the following:
    • Vectors
    • Record-winning insects (largest, smallest, fastest fliers, most deadly, etc.)
    • Historical info. (safe side, horrible test making at state had at least five questions on this subject)
    • Invasive species

Resources

The following guides are highly recommended:

  • Audubon Field Guide to Insects and Spiders: official field guide of the Entomology event, on which taxonomic scheme and questions are based on, has nice colored pictures and good bug descriptions, good for general insect knowledge; -note- this field guide groups bugs into groups based on their basic appearance rather than their correct phylogenetic groups (not good since the insects in here must be ID'd according to family and order), is also rather outdated regarding dates and population statistics, but contains the most reliable information simply because the test will be based on it.
  • National Wildlife Federation Field Guide to Insects and Spiders & Related Species of North America: contains close-up color photographs with informative description, very up-to-date; -note- has more than 2,000 photos of over 940 species, which may be confusing. However, if you highlight only the necessary insects with the necessary families, the guide becomes much more clear.
  • Peterson Field Guides: Insects - shows differences between different insects, has all insects on insect list; -note- contains a lot of information on how to collect and preserve an insect, which may not be useful when preparing for this event.
  • Smithsonian Handbooks: Insects - really nice pictures, great for nymphs and larva identification; -note- thin and is best utilized as a supplement (the first two/three field guides are better suited for use during the event)

Good Links

Soon to come:

  • Insect Behavior

Dichotomous Keys

On the tests, you may be asked to create a simple dichotomous key for identification of various insects. To create, just remember some simple tips:

There should be one less number of steps than number of insects you're including in the key.

You want to start off by dividing the insects into groups. If they do not have the insects already identified for you, then quickly identify them. For example, if they give you a house fly, a mantid, a dragonfly, and a mosquito, you'll divide them like this:

1. Two pairs of wings...................................go to 2

1. One pair of wings.....................................go to 3

Keep them very basic at first, then eventually divide them into more specific groups.

For example, you could then divide the two groups into colors, or whatever is most convenient.

Keep dividing the groups until you end up with the final step(since there are four insects in this case, there will be three steps) leading to the final insect being identified.

Human Impact

A very important aspect of this event is learning about how insects impact humans, the environment, and the world. Usually tests will feature stations with questions regarding identification and human/environmental/economic impact. Some insects are very prominent pests, such as certain species of Coleoptera, while others are highly beneficial, such as butterflies or bees that pollinate.

Beneficial Insects

Insect populations can have a positive impact on humans in a variety of different ways. They can be sources of food, decompose organic matter, manufacture products such as silk and honey, recycle carbon/nitrogen/other essential nutrients, and control populations of harmful invertebrates including other insects. Some are also valuable organisms to study for scientific and technological advances. Others have medical and therapeutic value.

Harmful Insects

In addition to having a positive effect on humans, insects can be very harmful. For example, some insects damage crops/trees and destroy products such as wood and paper. Many termites can destroy entire homes. Some can bite or sting, and many vector diseases. Others are household pests and parasites.

Disease Vectors

As stated above, many insects serve as vectors for diseases. Arbovirus is a term used to refer to a group of viruses that are transmitted by arthropod vectors. It is an acronym (ARthropod-BOrne virus). Haematophagous insects feed on blood at some stage of their life.

Insect Disease Vectors
Name of Insect Disease
Siphonaptera (fleas) Plague
Culicidae (mosquitoes) Malaria, filarisis*, arboviral encephalitides, dengue fever, Rift Valley fever, West Nile encephalitis viral infection
Calliphoridae (blow flies) Dysentery rabbit haemorrhagic disease, flystrike, salmonellosis

*Only female mosquitoes of the genus Anopheles transmit malaria and filarisis

Recommendations For Group Members

Both team members should have a strong background in Environmental Science (AP Level). The team should be prepared for both types of events (visual: power point/pictures, and live specimens); a lack of practice in either area can result in false identifications. The team should be able to use various types of microscopes. Partners should spend a portion of their preparation near various habitats (if available) such as marshes, swamps, forests, grassland, etc. to observe certain native species in a natural habitat (bring plenty of sunblock & insect repellent).

More Resources

Entomology/Entomology Insect List

Biological ID Events
Herpetology · Ornithology · Forestry · Entomology