Chapter I: New blepharocerid material, related to Neocurupira is described as Forms A, B, C and D, and placed along with N. hudsoni in a hudsoni- complex. On the basis of variation in eye structure within the hudsoni- complex the subgenus Paracurupira is shown to be unwarranted. Because of the morphological similarities of the eggs, larvae and adults, N. chiltoni and N. tonnoiri are considered to constitute a species group. On the basis of larval and adult morphology, Peritheates intermedius is considered to be synonymous with p. turrifer. The areas of distribution of known New Zealand blepharocerids are given. Descriptions and keys to most of the larval instars of known New Zealand blepharocerids are given, as well as keys to the adults of Australasian genera of blepharocerids. The origin and evolution of Australasian and in particular New Zealand blepharocerids are considered. It is believed that blepharocerids arrived in New Zealand from the north, along land bridges, during the late Cretaceous. There is no evidence to suggest that Australian blepharocerids gave rise to New Zealand blepharocerids. Chapter II: The eggs of Neocurupira campbelli, N. chiltoni, N. hudsoni and N. tonnoiri are figured and described. The embryonic development of N. chiltoni is traced and, less fully, that of N. campbelli. Comparisons are made between the embryology of N. chiltoni and N. campbelli and that of certain chironomids, culicids and simuliids. It is concluded that the similarities existing between the embryology of the simuliids and blepharocerids may indicate phylogenetic affinities. Chapter III: The study areas, Purau Stream, Kaituna River and Bealey River, as well as some other blepharocerid habitats, are described and their similarities listed. The records of rainfall, temperatures and water levels from the study areas are given and some of their interrelationships considered. The effects of floods on the study areas and larval populations are considered. The velocity, oxygen saturation, dissolved solids and pH of the water in the study areas are considered and the relationships between water velocity, larval respiration rate and sucker attachment are discussed. It is concluded that the operation of the sucker is the main factor which enables blepharocerid larvae to inhabit swiftly flowing water. The more important floral and faunal associates are listed and the effects of the density and types of associates on larval blepharocerids are considered. The distribution of larvae in the study areas is considered and some of the possible limiting factors discussed. Water velocity is believed to be the main limiting factor. Movement of N. chiltoni larvae is described and the observations compared with previous work on other blepharocerid species. The movement and function of the larval mouth parts are described and figured. Observations show that larvae prefer thin layers of algae but do not select particular algal types. Prepupae select suitable pupation sites. The prepupae of N. campbelli and P. turrifer in contrast to these of N. chiltoni, form dense aggregations. The pupation sites of N. hudsoni are unknown. Pupae in swiftly-flowing water orientate the anterior end downstream. The attachment of the N. chiltoni larvae during pupation is considered. Observations indicate that the larval suckers maintain their attachment to the substrate until the cement secreted by the pupa hardens and the larval cuticle is sloughed off. The emergence of N. chiltoni adults is described and the part played by the hydrophobic nature of the adult body during emergence, ovipositioning and the avoidance reaction is considered. Normal flight, as well as the avoidance reaction, is described. The mouth parts and the anterior part of the alimentary canals of N. chiltoni and N. hudsoni are compared with those of Liponeura cinerascens a known predaceous blepharocerid. It is postulated that New Zealand blepharocerids do not feed, but may be able to take up water. The mating and oviposition behaviour of the adult blepharocerids studied is described and the difference exhibited by N. chiltoni established. In contrast to other New Zealand blepharocerids N. chiltoni oviposits below the surface of the water. Laboratory data and field observations on the longevity of N. chiltoni adults are given. The laboratory data show that there is no significant sexual difference, but the field observations indicate that the males live longer than do the females. The effects of a sexual difference in life span is considered and it is believed that this contributes to the imbalance of the sexes in adult collections. The sampling techniques used to determine life cycles are described and it is shown that at Purau and Kaituna N. chiltoni probably has two generations per year, whereas at Bealey Chasm N. campbelli, N. hudsoni and P. turrifer have only one generation a year, though some of the larvae take longer than one year to complete development. The differing life cycles are considered to be the result of temperature difference between the two localities. The sex ratio of pharate N. campbelli adults is shown to vary seasonally and to have a significant negative regression on mean water temperature, whereas that of N. chiltoni remains relatively constant throughout the year. The percentage of brachypterous pharate N. campbelli females is also shown to have a seasonal change and a significant negative regression on mean water temperature. It is suggested that the variations in sex ratio and in brachypterism are interrelated.