In this lab you will learn to use spot ID characters and dichotomous keys for identifying specimens in the major orders of insects.
The main objectives of this lab are to help you:
- distinguish between insect and non-insect arthropods
- learn to identify major orders of insects based on key characters
- identify (to order) the adult insects that you will submit with your insect collection.
You will need the following materials for this lab:
- Your collected insects
- How To Know The Insects 3rd edition, by R. G. Bland and H. E. Jaques
- Stereoscopic microscope or hand-held magnifier
- Date/Locality labels
- Labeling pen
- Step Block
- Cork observation block
During this lab session, we will focus on the orders of insects (adult stage) that you are likely to see and collect this semester.
1. Assemble your insect specimens, microscope, cork observation block, and labeling equipment.
Your insects should already be pinned, pointed, or spread according to the protocol you were given in Lab #1 (Meadow Field Trip). Each specimen should have a Date/Locality label showing where, when, and by whom it was collected (see Collection Instructions). Handle your specimens with great care. Once they are dry, they become very brittle. Using the cork observation block to position your specimens for viewing under the microscope helps reduce accidental breakage.
2. Learn Spot ID characters for identifying insects to order.
First, be sure you can distinguish between insect and non-insect arthropods. Some non-insect arthropods look superficially like insects. Use the Arthropod Flowchart to familiarize yourself with the physical characteristics that can be used to distinguish among the various classes of arthropods. Only members of the class Insecta should be included in your insect collection.
Spot ID characters are physical traits that help you accurately distinguish one type of insect from another. Using these characters will save time and effort when you identify insects for your collection and will also improve your performance on the lab practicals. It can be risky to base your identifications on general appearance because many insects survive by “mimicking” other species. Using the Spot ID characters will keep you from being fooled, for example, by a fly that looks like a bee or a wasp. Very few people have learned to identify insects, so don’t be surprised if you become the local “expert” after taking this course!
Print the list of Spot ID Characters and then view the narrated slide show that illustrates how to recognize each character. The orders in this slide show are the only ones you will be expected to identify on a lab practical.
3. Use a Dichotomous Key for identifying insects to order.
Occasionally you will find an insect that’s hard to identify because it doesn’t seem to “fit a pattern” or else the spot ID characters are ambiguous. In such a case you will need to “key out” the insect using a stepwise logic tool called a Dichotomous Key. This is a series of paired statements or descriptions that are designed to gradually narrow down the field of possibilities until a conclusion is reached. Each step in the process involves a choice between two (sometimes more) alternatives. If you have never used a dichotomous key, you can learn more about how they work by watching the video at:
A dichotomous key to the orders of insects begins on page 40 of How to Know the Insects by Bland and Jaques. Practice with this key on a few “easy” specimens until you understand how it works.
Using a dichotomous key can be time-consuming -- that’s why it’s so important to learn the spot ID characters. You should be able to spot ID most of the insects you collect and just use the dichotomous key when you get stuck.
4. Identify the insects you have collected
Go through all the insects you have collected and sort them into orders based on spot ID characters.
Use the dichotomous key in How to Know the Insects for any specimens you cannot spot ID. A Flowchart for the Insect Orders may also help you narrow down the possibilities and save you some time going through the keys.
You can also get help with identification by posting a photo or description to the “What’s This” discussion board or bringing the specimen to my office. Either way, be sure to note when and where the insect was collected -- that often helps narrow down the possibilities.