AY Honors/Odonates/Answer Key

1. What are Odonates?

Odonates are an order of insects that is divided into 3 groups or suborders: Dragonflies and Damselflies and a third minor suborder. Enthusiasts generally refer to them as “Odes”.

2. Know how many species of damselflies and species of dragonflies are in your Country (or State/Provence) and Continent and Worldwide.

Ontario has 169. North America has 433. Over 5500 worldwide.

3. How do dragonflies and damselflies differ?

These two groups can easily be separated by 2 characteristics: the Damselflies are much smaller and frailer built, and hold their wings folded when resting rather than open as among the dragonflies (except for the Spreadwings which are damselflies that hold their wings open).

4. What separates Odes from other insects?

Odonates can be distinguished from all other insects by:

1. having 4 mesh-veined, equal sized wings,
2. large eyes that comprise most of the head,
3. large thorax that comprises the bulk of the body,
4. elongated, very thin multi-segmented abdomen. They are very strong fast fliers that seem to be able to go in most any direction, make immediate sudden stops, and are known to travel many miles from their normal habitat.

5. What other insects look a bit like odes?

Other orders of insects that might be confused with Odonates are: Mayflies, Stoneflies, Lacewings and Ant Lions, and Caddis flies.

6. Describe and draw the life cycle of an ode.

Odonates have what is considered a simple cycle of egg—larva—adult.

Eggs

Eggs are generally laid in or sufficiently near water where water will soon rise and cover. Generally they hatch in about a week although eggs lie in or near temporary pools will hatch sooner or even be delayed several months. The females of some damselflies will actually submerge themselves for an hour or more while laying her eggs.

Larvae

The larvae, called nymphs or naiads will use most any kind of temporary or permanent aquatic habitat. Some will even survive in moist substrates under rocks in otherwise dry streambeds or ponds. They do not look at all like the adults they will become and will molt their exoskeletons between 7 and 18 times in a period of a few months to several years before the final change comes into adulthood.

During this time they are voracious eaters of most anything that moves under water from mosquito larvae to even small fish and amphibians. The change from larva to adult may take a few hours to a few days. The nymph will climb out of the water as far as 30 meters horizontal and 10 meters vertical. Emergence generally occurs at night but some species are diurnal. A split will develop down the back and the adult will then slowly pull itself free of the old larval shell. As it does so, the new exoskeleton slowly hardens, the wings extend and harden. Once it is fully hard it is ready for flight.

Adults

Sexual maturity will be reached within a few hours to over a week depending on the species. During this time they continue their habit of being very voracious eaters consuming large numbers of mosquitoes, other small insects and even other Odonates.

7. Know the following terms regarding Odonates:

a. Exuviae

is a term used in biology to describe the remains of an exoskeleton that is left after an arthropod (insect, crustacean or arachnid) has moulted. The exuvia of an animal can be important to biologists as it can often be used identify the species of the animal and even its sex.

b. Ocelli

is a type of photoreceptor organ in animals. Also called "simple eyes", ocelli are miniature eyes capable of sensing light but not distinguishing its direction. See also stemmata, which are structurally similar. Ocelli are found in many invertebrates. Insects in particular have two types of ocelli, dorsal ocelli and lateral ocelli.

c. Crepuscular

is a term used to describe animals that are primarily active during the twilight -- at dawn and at dusk.

d. Cerci

are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans.

e. Pruinescence

is a "bloom" caused by pigment on top of an insect's cuticle that covers up the underlying coloration, giving a dusty or frosted appearance. The pruinescence is commonly white to pale blue, but can also be gray, pink, purple, or red; these colors may be produced by Tyndall scattering of light. When pale in color, pruinescence often strongly reflects ultraviolet.

f. Wing Veins

g. Wing Cells

h. Compound eyes

i. Segments

j. Pterothorax

k. Labium

l. Forewing

m. Pterostigma

n. Hindwing

o. Frons

8. Of what value are odes and why should we study them?

As mentioned above, their eating habits make them one of nature’s most beneficial insects from man’s perspective. Their value in mosquito control is immeasurable. They are among some of the most colorful, eye-catching and attractive of all insects. They also are a good indicator of the environmental conditions in their breeding habitat.