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About the Author
John C. Abbott is Lecturer in the Section of Integrative Biology, Curator of the Brackenridge Field Laboratory Insect Collection, and Research Associate of the Texas Memorial Museum at the University of Texas, Austin.
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Dragonflies and Damselflies of Texas and the South-Central United StatesTexas, Loiusana, Arkansas, Oklahoma, and New Mexico
IntroductionDragonflies and damselflies make up the insect order Odonata. They are found worldwide, except for Antarctica. Most treatments recognize three suborders within the Odonata. The names of these groups derive from the relative shapes of the fore- and hindwings. The dragonflies belong to the suborder Anisoptera, the hindwings of which are broader than the forewings. The damselflies, suborder Zygoptera, have fore- and hindwings of the same shape. The members of a third suborder, the Anisozygoptera, are often called "living fossils" and can be recognized by a mix of the characters seen in the Anisoptera and Zygoptera. This group contains only two extant species, both restricted to East Asia. In most parts of the world the term "dragonfly" refers to members of any of the three suborders, but in North America the term usually refers specifically to members of the Anisoptera. In this book I will refer to dragonflies and damselflies collectively as Odonata or odonates.
Because odonates are remarkably distinctive in appearance, and unique in many other aspects of their biology, they are seldom mistaken for other insects. Some 5,500 species areknown worldwide, just 433 of them in North America north of Mexico. Odonata, especially in the tropics, is one of the larger aquatic insect orders, giving its members, wherever they occur, an ecologically important role in aquatic ecosystems. (Other insects that spend a substantial period of their life in the water include mayflies, order Ephemeroptera, and stoneflies, order Plecoptera.)
The Odonata represent one of the most primitive living insect groups. The earliest fossil odonates are some 250 million years old. Members of the order Protodonata, the probable ancestors of Odonata, lived more than 300 million years ago, and some had wingspans greater than 71 cm (2 feet)! The closest living relatives of the Odonata are the mayflies. Odonates exhibit many primitive features, including the inability to fold their wings flat and fanlike over the abdomen, a trait they share with the mayflies. The wings have dense venation, and each wing is fully functional and independently movable. The robust thorax is strikingly skewed, forcing the legs forward and the wings backward.
Even the most casual observer must appreciate the phenomenal agility that odonates display in flight. Throughout human history they seem to have spawned not only interest but also fear. Their large size and fast, buzzing flight are the basis for such names as "devil's darning needles" and "horse stingers." Although some of the larger dragonflies can pinch a finger placed in the mouthparts, odonates do not normally bite humans. These names may have originated in part from occasional instances in which a female dragonfly mistakes the leg of a wader or river rafter for a plant when laying her eggs. Though I have never experienced this firsthand, those that have confirm that having a dragonfly attempt to lay eggs in you is painful!
Not only are odonates among the most beautiful of insects, they are also beneficial. Both dragonflies and damselflies are voracious predators, both as aquatic larvae and as adults, and one of their main prey items is mosquitoes.
Habitats and Zoogeography of the South-Central United States
The south-central United States, as defined herein, includes Texas and its four surrounding states. The area covered is approximately 1.2 million [km.sup.2], of which 695,000 [km.sup.2] are in Texas. The region encompasses ten biotic provinces (Fig. 1). The Mississippi River forms the eastern boundary of the region (which means that the few parishes of Louisiana that lie east of the Mississippi are not covered), and the Apachian and Navahonian biotic provinces bound the western edge.
A considerable amount of work has been done on the distribution of vegetation types in Texas (Bray 1901, 1905; Carter 1931; Tharp 1926, 1939), Louisiana (Viosca 1933; Holland 1944), Arkansas (Turner 1935; Stroud & Hanson 1981), and Oklahoma (Ortenburger 1928a,b; Bruner 1931). There is a tremendous variety in the environments available for plant and animal communities, which are determined largely by climatic conditions and topography. A north-south line passing through central Oklahoma and Texas divides our region into areas of moisture sufficiency and moisture deficiency (Blair 1950), thus dictating plant and animal distributions in the region. Cope (1880) recognized three major biotas in Texas: a Sonoran fauna, an Austroriparian fauna, and a Neotropical fauna. I recognize a further division into ten distinct regional biotic provinces, as outlined by Blair and Hubbell (1938), Dice (1943), and Blair (1950), and as shown in Fig. 1. These provinces, which differ in topography, annual temperature range, vegetation, soil type, geology, and climate, have been given the names Apachian, Austroriparian, Balconian, Carolinian, Chihuahuan, Coloradan, Kansan, Navahonian, Tamaulipan, and Texan. The provinces are useful in detailing the distribution of Odonata, biologically vs. politically, within our region, as you will see in the individual species accounts.
Mean annual precipitation ranges from 147 cm/yr in the moist eastern parts of the region, such as New Orleans, to less than 25 cm/yr in the arid western areas, such as El Paso. Most of the precipitation falls during the months of March to May. Temperature is also an important factor in dictating the distribution of plant and animal communities, and ranges from an annual average of 22.8° C ( 73.4° F) in subtropical Brownsville, Texas, to 12° C (53° F) in the Texas panhandle, resulting in a shorter growing season in the latter. Major vegetation types include eastern pines and hardwoods, central prairies and grasslands, western semidesert areas, and western montane forests. Elevation ranges from sea level along the coastal areas to 4,011 m (Wheeler Peak, Taos County, New Mexico) in the Carson National Forest. The major watersheds in the region (Fig. 2) drain in an eastward or southeastward direction, and nearly all of them enter or approach the Austroriparian province. These stream systems provide important dispersal routes for the westward distribution of species of the Austroriparian province into the more arid, treeless environments (Blair 1950).
The Austroriparian province, as defined by Dice (1943), encompasses the Gulf coastal plain from extreme east Texas to the Atlantic Ocean. This biotic region's western boundary is demarcated by the availability of moisture. The typical vegetation types include longleaf pine (Pinus palustris) and loblolly pine (P. taeda) and hardwood forests variously consisting of sweetgum (Liquidambar styraciflua), post oak (Quercus stellata), and blackjack oak (Q. marilandica). The lowland hardwood forests of the southeastern portion of this province are typically characterized by magnolia (Magnolia grandiflora), tupelo (Nyssa sylvatica), and water oak (Q. nigra) in addition to those trees mentioned above. Other plants typical of this region include Spanish moss (Tillandsia usneoides) and palmetto (Sabal minor).
The Texan biotic province constitutes a broad ecotone between the forests of the Austroriparian province in the eastern portion of this region and the western grasslands. The Balcones Escarpment forms an abrupt boundary to the west, otherwise delineated by a line based on soil type. This area was once characterized by tall-grass prairies supported by clay soils, but cultivation of much of the area has led to sandy soils characterized by combination oak-hickory forests, dominated usually by post and blackjack oaks and hickory (Carya texana). Thornthwaite (1948) classified this province as having a moist, humid climate, but receiving little water beyond that required for growth. The drainage pattern of the Texan province is an important biogeographical feature (Blair 1950). The Red and Trinity rivers, along with their tributaries, drain the northern part of this province. Both of these rivers enter the Austroriparian province before emptying into the Gulf. The southern portion of this province is drained largely by the Brazos, Colorado, San Marcos, and Guadalupe rivers.
One of the unique features in this province is the Arbuckle Mountains in south-central Oklahoma, just north of the Red River. This area is dominated by granite and travertine limestone geologic formations. One of the most prominent of these formations is in Turner Falls Park near Davis, Murray County, Oklahoma. Within the park, there is a 25 m waterfall on Honey Creek.
For the Kansan province, I follow Blair (1950), who delineated the province differently than did Dice (1943). Dice limited the province, excluding the Permian redbeds, while Blair included the areas north of the Edwards Plateau and south of the Red River. The province is characterized by a mixture of eastern forest species and western grassland species. Notable exceptions to the monotonous prairies of this province are Palo Duro Canyon State Park and Caprock Canyon State Park, which have been characterized as relict habitats. Moisture decreases from east to west in this province, and Thornthwaite (1948) considered the region moisture-deficient.
The Balconian biotic province is defined by the Edwards Plateau of Texas and derives its name from the Balcones fault zone that forms its southern and eastern boundaries (Blair 1950). It is characterized by scrub forests of juniper (Juniperus spp.) and oaks (Quercus spp.), including stunted live oak (Q. virginiana).
Farther south, the Tamaulipan province extends from southern Texas into eastern Mexico. This semiarid region is dominated by mesquite (Prosopis glandulosa), Acacia spp., Mimosa spp., and prickly pear cactus (Opuntia spp.). Thornthwaite (1948) noted a marked deficiency of moisture for plant growth, though some growth occurs year round. This province is drained in the north largely by the Nueces River and its tributaries, and is poorly drained in the southern portion by minor tributaries of the Rio Grande. In the Brownsville region, to the south, the province becomes subtropical.
The Chihuahuan province includes the Trans-Pecos area of Texas, excluding the Guadalupe Mountains. It extends southward into the Mexican states of Chihuahua and Coahuila and is drained largely by the Rio Grande. This biotic province is more diverse in physiographic features than all others in the region (Blair 1950). The climate in this area is arid and moisture-deficient (Thornthwaite 1948), and the vegetation is variable, but basin areas up to 1,500 m in elevation include grasses, desert shrubs, and creosote bush (Larrea tridentata). Streams in this area are usually small and intermittent; those that are permanent are usually springfed. The various mountains, including the Chisos and Davis ranges, show a vertical zonation of plant communities, with elevations above 1,500 m dominated by Emory oak (Quercus emoryi) and cedars (Juniperus spp.).
The Navahonian province includes most of New Mexico and barely enters the northern edge of western Texas (Culberson County) at the southern extension of the Guadalupe Mountains. A vertical zonation in elevation similar to that of the Chihuahuan province characterizes this area. Trees dominant at elevations above 2,500 m include various pines (Pinus spp.), oaks (Quercus spp.), and Douglas Fir (Pseudotsuga menziesii).
Small portions of the Carolinian (northern Arkansas), Coloradan (northwestern New Mexico), and Apachian (southwestern New Mexico) provinces are also found within the region covered by this book. These peripheral provinces are home to several odonates whose ranges barely extend into the south-central United States.
Life History of Odonata
As is true of any living organism, reproduction is a critical stage in the life cycle of odonates. It may take an individual adult anywhere from a day to several weeks, depending on the species, temperature, availability of food, and other environmental factors, to become sexually mature. Upon maturity, the male will, in most species, patrol a territory he has established over and around water. The male will search for females in this territory, and will defend it against other males of his species and occasionally males of other species. At some point a receptive female looking for suitable egg-laying areas is seized by the male. This capture usually takes place in midair, the male flying over the female and grabbing her head and thorax with his legs. In damselflies, the male grasps the female's prothorax (the segment of the thorax behind the head) with the clasping structures at the tip of his abdomen (this is the tandem position).
In dragonflies he grasps her head, and in aged females of some larger species (darners) the resulting damage to the eyes is often noticeable. The male will then curl his abdomen around so that sperm can be transferred from the genital pore on the ventral side of his segment 9 to the accessory genitalia located on the ventral side of his segment 2. This usually happens quickly, and the male then straightens his abdomen so that the receptive female can curl her abdomen around, such that her genital opening on the ventral side of segment 8 is in contact with his accessory genitalia on segment 2. It is not unusual to see odonates in this wheel position. They may remain in this position, usually protected within vegetation, for minutes or hours, depending on the species. Still others copulate while in flight. (A number of the color photos in this book are of mating pairs.) Females will mate more than once, and in at least some species, males are known to remove the sperm from previous males before mating.
Female damselflies, petaltails, and darners all lay their rod-shaped eggs using a specialized structure called the ovipositor. They use the bladelike structures of their ovipositor to make slits in the soft tissues of plant stems, where they then lay their eggs. These eggs may be laid above, at, or below the water line. In other odonate families the eggs are generally more round in shape and often have a gelatinous covering. These eggs are laid in or near water or in an area that will fill with water. Female Spiketails employ a specialized ovipositor in sewing-machine fashion to deposit eggs in the substrate of shallow streams. The eggs will generally hatch in about a week. Eggs laid in temporary pools, however, will hatch more quickly, whereas others may be delayed for months. The male may continue to grasp the female (in the tandem position) while she lays eggs, or he may release her, but he will remain hovering or perched nearby to guard against intruding males. Females of some species of damselflies will actually submerge themselves underwater for an hour or more while ovipositing. Regardless of whether a female descends underwater or not, she, and often the male, are vulnerable to predation by fishes, frogs, birds, spiders, and other insects during this time.
Excerpted from Dragonflies and Damselflies of Texas and the South-Central United States by John C. Abbott Copyright © 2005 by Princeton University Press. Excerpted by permission.
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Table of Contents
Habitats and Zoogeography of the South-Central United States 1
Life History of Odonata 4
Seasonality of Odonata in the South-Central United States 6
Studying Odonata 8
Photographing Odonata 9
External Anatomy of Adult Odonata 10
A Guide to the Species Accounts 15
DAMSELFLIES (Suborder Zygoptera) 19
Broad-winged Damsels (Family Calopterygidae)21
Spreadwings (Family Lestidae) 29
Threadtails (Family Protoneuridae) 46
Pond Damsels (Family Coenagrionidae) 52
DRAGONFLIES (Suborder Anisoptera) 149
Petaltails (Family Petaluridae) 151
Darners (Family Aeshnidae) 153
Clubtails (Family Gomphidae) 176
Spiketails (Family Cordulegastridae) 215
Cruisers and Emeralds (Family Corduliidae) 218
Skimmers (Family Libellulidae) 240
Additional Species 309
Checklist of South-Central United States Odonata 311
Field Guides and Other Reference Works 319
Odonata Societies 319
Sources Cited in Text 319
Photo Credits 335