A contribution to the knowledge of the odonata
Abstract
Theories concerning the origin of insect wings and flight are reviewed
and a new scenario for their origin proposed. It is suggested
that environmental conditions of the small stream were responsible for
the evolution of insect flight, and that thermoregulation as well as
respiration was important in the preadaptation of wings. The possibility
that the five paired convex-concave vein systems each represented a
dorsal-ventral blood channel is suggested.
Odonate wing vein homology and nomenclatural systems, and phylogeny
are reviewed. The process of vein loss is evaluated in the Palaeoptera
and a new system of odonate wing vein homologies proposed. The odonate
wing mechanism is analyzed and the heretofore overlooked discal nodus
characterized. Reevaluation of the comparative morphology of fossil
and recent Odonata indicates that Protozygoptera and Protanisoptera represent
evolutionary side branches, that the Anisozygoptera is polyphyletic,
and that Isophlebiidae and Calopterygoidea are the most generalized
Odonata known.
Previous scenarios explaining evolution of the unique odonate copulatory
process are reviewed. Considering the copulatory behavior of
the Calopterygoidea generalized supports evolutionary trends toward male
domination and in-flight completion of the process. Assuming direct
sperm transfer the original odonate mode requires that originally oviposition
be in tandem and that sperm transfer to and from male anterior
abdominal sterna be accidental. In contrast, assuming an original indirect
transfer of sperm leads to a copulatory sequence similar to that
of the Odonata. The proposed scenario differs from others in that extraordinary
postures are not envisioned, the process is completed at
rest, and the odonate tandem hold is developed prior to copulation.
Anisopteran morphology and phylogeny are reviewed and reliable
dentification keys developed for North American families and genera,
and for 180 anisopteran species collected in Virginia and vicinity.
Each species is described and photographed, including seven new species.
The biogeography of Virginia Anisoptera is best explained by overlapping
biotic regions, the fauna being a mixture of eastern North American,
boreal, and tropical elements. New efficient methods for collecting,
preserving, and rearing Odonata are described.
Collections
- Doctoral Dissertations [14916]