Odonata

blue dragonfly or Odonata

Introduction

Dragonflies and damselflies. A medium sized order of about 5500 species worldwide, mostly tropical, 11 families and about 415 species in North America, north of Mexico. Paleoptera- Hemimetabolous.

Recognition

Nymphs- external wingpads present, chewing mouthparts with labium modified into a mask-like extendible structure. Adults- 2 pairs of membranous non-folding, wings, antennae short and bristle-like, abdomen without long, terminal filaments.

Life cycle

Eggs may hatch in a few days to a few weeks, or undergo diapause until spring or until flooded with water. The first nymphal stage, the pronymph soon molts into the first instar. The nymphs grow through many instars (10 to 15) over a couple months to a few years. Mature nymphs climb out of the water (mostly at night) before the final molt. Emergence may be fairly synchronous in temperate areas or non-seasonal in more tropical areas. Most temperate species are univoltine with a few semivoltine. Adults may live for several weeks. Young adults forage widely for food, but usually return to the area of a suitable aquatic habitat to seek mates. Males may patrol territories. Males must transfer sperm from the genital opening on abdominal segment 9 to the penes on abdominal segment 2. Males guard females in a tandem position, they mate in a wheel position. Males may escort the females during egg laying. Eggs may be placed in plant tissue (endophytic), or otherwise placed (exophytic) into the substrate, upon the water, or above the water.

Trophic roles

Nymphs and adults are uniformly active predators. Nymphs sit-and-wait or slowly stalk their prey. Adults may assume the swarm of the prey, unlike birds and bats.

Communities

Fairly complex in warm, vegetated, permanent lentic habitats with many species organized by body size, habits (sprawlers, climbers, and burrowers), and season. Fewer species are typically present in warm streams, temporary ponds, and cold lakes. They are usually absent in cold mountain streams.

Economic importance

May help control nuisance insects, but not selective for these; may feed on fish fry, important intermediate consumers in many systems, fish food, some fishing fly patterns.

Zoogeography

An ancient group occurring on all continents. Many species are widely distributed, others are more restricted (often in springs). Some of the better dispersers with general habitat requirements also found on islands. A few island and forest species have terrestrial nymphs. Some species migrate.

Collecting

Nymphs are usually obtained be scooping up suitable substrate and picking the nymphs by hand. Exuviae may be found on emergent vegetation and other surfaces. Capturing adults can be difficult. Few will be found unless the weather is warm to hot and sunny. Most damselflies are easily netted or picked up sweeping shoreline vegetation. Dragonflies must usually be hunted individually, sometimes with a gun, but usually with a large diameter, light-weight net. They are most vulnerable from below and behind. Scouting their habits before swinging the net is usually wise.

Rearing

Mature nymphs can often be reared if held in a screen container allowing access to the surface and sufficient room for the adult above water. Adults may not be fully colored for a couple days to a couple weeks.

Preservation

Nymphs are best fixed in Khale's solution and transferred to 70% ethanol in a few days. Adults are usually preserved dry in envelops with the wings folded together over their back. Ideally, freshly captured adults are confined within folded pieces of paper that are secured by a staple or paper clip. They are kept alive for a while to allow them to void the intestinal track. They are then submerged overnight, while still in their paper envelopes, in acetone. This dissolves fats, oils, and waxes as well as removes water by osmosis. The specimens are removed from the acetone and allowed to quickly dry. They are ultimately stored in clear envelops with their collection data in a pest-proof container. At the very least, the adults can be folded into a piece of paper and allowed to die and dry in a warm protected place.

Taxonomy

A popular group that is very well studied. Many species lists and faunas are available. Most specimens (males, females, and nymphs) can be identified to species. Still with a moderate rate of new species discoveries. Many current studies emphasize behavior, competition, predation energentics, etc.

Quick recognition of the nymphs of the neartic families

Suborder Zygoptera- nymphs slender with 3 caudal gills
1. Calopterygidae- first antennal segment as long as the rest combined
2. Lestidae- prementum distinctly stalked
3. Coenagrionidae- prementum not stalked
4. Protoneuridae from South Texas is omitted
Suborder Anisoptera- nymphs robust without external caudal gills
1. Gomphidae- labium flat, antennae 4 segmented
2. Petaluridae- labium flat, antennae 6-7 segmented, segments short and thick
3. Aeshnidae- labium flat, antennae 6-7 segmented, segments slender
4. Cordulegastridae- labium spoon-shaped, palpal lobe with large irregular dentations
5. Macromiidae- labium spoon-shaped, head with frontal horn
6. Corduliidae- labium spoon-shaped, palpal lobes with deep regular notches
7. Libellulidae- labium spoon-shaped, palpal lobes with shallow notches

Montana Species list

Reference update

Carle, F.L. 1993. Sympetrum janeae spec. nov. from eastern North America, with a key to nearctic Sympetrum (Anisoptera: Libellulidae). Odonatologica 22(1):1-16.
Carle, F.L. 1992. Ophiogomphus (Ophionurus) australis spec. nor. from the gulf coast of Louisiana, with larval and adult keys to American Ophiogomphus (Anisoptera: Gomphidae). Odonatologica 21(2):141-152.
Donnelly, T.W. 1992. The Odonata of New York state. Bull. Amer. Odonatol. 1(1)45-51.
Garrison, R. W. 1991. A synonymic list of the new world Odonata. Argia 3:1-30.
Dunkle, S.W. 1990. Damselflies of Florida, Bermuda, and the Bahamas. Scientific Publishers, Gainesville.
Dunkle, S.W. 1989. Dragonflies of the Florida peninsula, Bermuda, and the Bahamas. Scientific Publishers, Gainesville.
Evans, M,A., 1988. Checklist of the Odonata of Colorado, Great Basin Natur. 48:96-101.
Garrison, R.W. 1984. Revision of the genus Enallagma or the United States west of the Rocky Mountains and identification of certain larvae by discriminant analysis (Odonata: Coenagrionidae). Univ. California Publ. Ent. 105:1-129.
Miller, K.B. and D.L. Gustafson. 1996. Distribution records of the Odonata of Montana. Bulletin of American Odonatology 3:75-88.
Miller, K.B. and M.A. Ivie. 1995. Enallagma optimolocus, a new species of damselfly from Montana (Odonata: Coenagrionidae). Proc. Ent. Soc. Wash. 97: 833-838.
Miller, P.L. 1987. Dragonflies. Cambridge University Press, Cambridge.
Roemhild, G. 1975. The damselflies (Zygoptera) of Montana. Montana Agricultural Experiment Station Research Report 87, Montana State University, Bozeman, 53pp.

19 NOV 1995 updated on 20 JULY 1996 D.L. Gustafson

Aquatic Invertebrates of Montana