Territorial Behavior in Dragonflies and Damselflies

by Jim Pierson, Wayne Cowell,

and Tom Freeman

Overview

Competition among organisms for resources is well documented in the animal kingdom. Resources include habitat, food, and mating partners. The following activity will examine the territorial, mating, and ovipositional behavior in insects of the order Odonata (Dragonflies and Damselflies).

Biological Concepts

• territoriality • proximate and ultimate causation

• mating behavior • competition

• sexual dimorphism • oviposition

Class Time

Depending on the proximity of the water source, the lab could take as much as two fifty-minute class periods.

Background Information

Dragonflies and damselflies both belong to the insect order Odonata. Damselflies are generally smaller than dragonflies, and when at rest their wings do not lie flat as in dragonflies but are folded up over their thorax (Figs. A and B). Both groups are carnivorous both as adults and as nymphs. The odonata are harmless and do NOT bite or sting. The adults roam through the air and prey on other small flying insects while in flight.

Dragonfly

In many species the males are very territorial. The males will stake out and defend their territory from other males, and attempt to mate with any mature receptive female that enters his space. It is quite common to see males chase off intruders.

In general the males tend to be more brightly colored than the females, but can easily be sexed by examining the end of the abdomen for an ovipositor in females and short cerci in males (Figs C and D).

The two sexes frequently spend considerable time in tandem during mating and oviposition (Fig. E).

Fig. E

(Redrawn from Waage 1984)

Male dragonflies and damselflies are peculiar among insects in having a secondary copulatory organ located at the anterior end of the abdomen (second segment). Before the male can mate it must transfer sperm from his primary copulatory organ at the tip of the abdomen to the structure on the second segment. Mating commences with the male grasping the female with abdominal claspers. The pair then assume the "wheel position" with the tip of the female's abdomen and thus her sexual apparatus engaging the male's secondary copulatory apparatus. The male first uses his penis to remove any sperm left by a previous male before inseminating her himself (Figs. F and G).

Fig. F

Fig. G

(Redrawn from Waage 1984)

The female will then lay eggs while still in tandem or after the male disengages in copulation. Odonata lay their eggs in the open water, or on nearby emergent or slightly submerged vegetation (Fig.H).

Fig. H Ovipositing Female

(Redrawn from Waage 1984)

In the species where the female detaches from the male before oviposition, the male will remain nearby on guard and will chase off other males that come near. An unprotected female, after she begins ovipositioning, may be approached by another male who may grab her and fly off in tandem. Eggs of the order Odonata will drop to the bottom muds of streams or ponds and develop into an aquatic nymph stage until they emerge one year later to propigate the species.

The nymphs (Fig. I and J) that hatch from the eggs are aquatic and breathe by the use of gills in their abdomen. The gills of the damselflies are in the form of three leaflike structures at the end of the abdomen; in dragonflies the gas exchange occurs internally as water is drawn into the abdomen. Most species have a single generation a year, with the egg or nymph overwintering. In some large dragonfly species the nymphal development time can last up to three years or more.

When the time is right, the aquatic nymph emerges from the water (depending on the species, trees, rocks, mud, any sort of vegetation, etc, might be used). The outer skin of the nymph splits along the back of the thorax and the young dragonfly emerges. Over the next few hours, various changes, such as wing spreading, take place leaving the insect very vulnerable to predation or disturbance. If all goes well, the insect will undergo its maiden flight, often a short relatively floppy flight away from the water, when both the wings and body have sufficiently hardened. The insects leave the water for a period up to a couple of weeks while they become sexually mature. During this maturation, the males of some species undergo dramatic changes in coloration.

MATERIALS

• Aerial Collecting Nets

• Field Guides

• Cameras (Still and Video)

• Killing Jars With Chemicals

• Pinning Boards

• Dowl With Fishing Line Attached and Decoy

• Waders (depending on depth of water)

• Insect Display Cases

• Aquatic Collecting Net (optional)

TEACHER PREPARATION AND DIRECTIONS

1) The teacher needs a suitable freshwater habitat for the class which has stable banks and no obvious hazards.

2) A few days before the lab, the teacher should scout the area out to make sure there are active adult populations exhibiting the desired behaviors. One should gather samples of the various species of dragonflies or damselflies beforehand, or show pictures of them from a field guide, so that the students are familiar with the morphological differences between the species. Depending on the prior knowledge of the students, a quick description of the three major parts of insects may be necessary. It may also be helpful to disseminate information regarding the classification of the insects in the animal kingdom, i.e. order Odontata.

3) A brief description of the differences between male and female members of the order Odontata should follow, as well as a short lesson on the life cycle of dragonflies and damselflies including their territorial, mating, and ovipositional behavior. The teacher may wish to have the students formulate hypotheses regarding the evolution of the mating behavior of dragonflies and damselflies.

4) Once at the field site have students try to determine the nmber of different species. Have them pick one of the species of dragonflies or damselflies and determine if the males are territorial and/or exhibit male guarding behavior.

5) Have students locate the territory of a specific male. Next have them tie a preserved male or female specimen of the same species on the end of clear fishing line or black thread attached to a dowl and dangle in the male's territory swinging the specimen back and forth simulating flying. Have students observe the interactions. The male may try to chase off the new male intruder, attempt to mate with the female, or ignore them completely. Students can make and attach to the dowl their own odonata decoys of various sizes and colors, and observe the results. An interesting experiment is to paint a male specimen the color of a female and test the effect.

EXTENSIONS AND VARIATIONS

• production of video by students

• production of 35 mm slides of still shots by students

• abstracts of articles from encyclopedias or the Internet

• use taxonomic keys to identify the specimens collected to the genus or species level

• display insects of other orders which are related to damselflies

• trips to local museums which display insect collections

• have a local entomologist talk about selected species, bring specimens, pictures, or explain the role of dragonflies, damselflies, and their relatives in the local environment

• simulate an oviposition site in a small stream by placing a piece of wood across the stream with nails sticking into it. Attaching long leaves (3-5) to the nails facing downstream will simulate an oviposition site to the flying odonates. Observe and report any females or other activities that utilize the site for laying their eggs.

RESOURCES

Web Sites of Interest:

Dragonflies and Damselflies (Odonata Information Network) -- http://www.afn.org/~iori/

The International Odonata Research Institute -- http://www.afn.org/~iori/ioriintr.html

The Odonata Information Network -- http://www.afn.org/~iori/oinlinks.html

The Odonata Homepage -- http://www.jcu.edu.au/dept/Zoology/auxillary/odonata.htm

Alcock, J. (1992). The Duration of Strong Mate-Guarding by Males by the Libellulid Dragonfly Paltothemis lineatipes: Proximate Causation. Department of Zoology, Arizona State University, Tempe, AZ, pp. 507-515.

Corbet, P. S. (1980). Biology of Odontata . Department of Zoology, University of Canterbury, Christchurch, New Zealand, pp. 189-209.

Waage, J. K. (1984). Sperm competition and the evolution of odonate mating systems. In Smith, R. L. (ed.), Sperm Competition and the Evolution of Animal Mating Systems . Academic Press, New York, pp. 251-290.

Acknowledgments

This activity was adapted from a demonstration presented by Dr. John Alcock (Arizona State) at the 1996 Howard Hughes Institute for High School Biology Teachers at Princeton University.

About the Authors

Wayne Cowell is a biology teacher at Standley Lake High School in Jefferson County Schools at 9300 W. 104th Ave. Westminster,CO 80021. (303) 465-1144 E-mail: wcowell@jeffco.k12.co.us

Tom Freeman is a biology teacher at Esperanza High School in the Placentia-Yorba Linda Unified School District at 1301 Orangethorpe Ave. Placentia, CA 92670.

(714) 779-7870.

Jim Pierson is a biology teacher at Abington Friends School in Jenkintown, Pennsylvania

He can be contacted at Abington Friends School, 575 Washington Lane, Jenkintown, PA 19046. Phone (215) 886-4350. E-mail: jpierson@afs.pvt.k12.pa.us

Name __________________________ Date ___________ Per _____

FIELD OBSERVATIONS:

1. How many different species of Odonata did you observe?

2. How did you tell the species apart?

3. Describe the habitat of the different species observed.

4. Select one species and try to determine the following information:

• differentiate between male and females

• the mating behavior

• territorial behavior of males

• mate guarding behavior of males

• ovipositional behavior of females

• make a colored drawing of both sexes

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