![]() Returning to the University of Florida, he earned a Ph.D. His ensuing graduate program at the University of Florida was interrupted by the military draft and one year of service in the Vietnam War. His pursuit of knowledge on aquatic insects intensified at the University of Wisconsin where he obtained his Bachelor of Science degree in 1968. Of particular impact was the discovery of the life cycle of dragonflies, as he witnessed the transformation of nymphs from an aquatic existence to adults that could mate in the air then return to the water to lay eggs. Tennessen grew up in the Wisconsin North Woods where he became fascinated with insects at an early age. A glossary and an index to scientific names are included. Appendix II contains a brief history of dragonfly nymph studies in North America. The habitus drawings of all genera are arranged according to family in five plates (Appendix I) although the book is intended as a lab manual, these plates conveniently allow for comparison based on nymph shape making field identification to genus possible in many cases. The final chapter discusses research opportunities on North American Anisoptera nymphs, including taxonomic needs, studies on structure and function, life history and microhabitat, water quality indices and conservation efforts. Methods for collecting, rearing, and preserving dragonfly nymphs and exuviae are presented. The importance of nymph characters in helping solve generic and specific distinctions and their role in phylogenetic studies is emphasized. Difficulties with past keys and descriptions, including errors, omissions and other shortcomings, are addressed. Measurements of total length, head width, and other variables for each species are provided in tables. Most of the characters used to distinguish all levels of taxa are illustrated a total of 702 figures, comprising 1,800 original drawings, along with selected photographs where necessary for clarity, accompany the keys. ![]() ![]() Morphological variation in character states was analyzed in order to assess the reliability of previously utilized characters and to discover new characters. Full-grown nymphs of all known species of each genus are keyed and diagnosed characters that apply to earlier instars are noted. A drawing of the habitus and diagnostic details for each genus are provided, along with additional diagnostic remarks and notes on habitat and life cycle for each genus, a map shows its geographic distribution in North America. Each family is further characterized, followed by a generic key. The families are then covered separately: Aeshnidae (13 genera), Gomphidae (17 genera), Petaluridae (2 genera), Cordulegastridae (2 genera), Macromiidae (2 genera), Corduliidae (7 genera), and Libellulidae (29 genera). The key separating the seven families in the region contains several new characters. Species are tabulated with references that provide the most detailed, accurate descriptions for each species that are inadequately described are so indicated. Nymphal external morphology is described and illustrated in detail, and all terms needed to navigate the dichotomous keys are defined. This monograph is the first of its kind devoted entirely to the dragonfly nymphs of North America north of Mexico, the focus being accurate identification of the 330 species of Anisoptera that occur in the region.
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