Relationships between gregarine infection in damselflies, wetland type, and landscape characteristics

Although human-modified landscapes are characterized by the loss of natural habitats, new habitats also can be created and exploited by many species. The importance of landscape change to invertebrate associations (particularly host-parasite associations) is understudied. Our objective was to determine whether prevalence and intensity of gregarine parasitism in the damselfly Ischnura verticalis (Say) (Odonata: Coenagrionidae) differed between 17 artificial and 7 natural wetlands in landscapes that varied in amount of forest and wetland cover and road density determined at spatial extents of 500m and 1km from each wetland. Wetlands were located in and around Ottawa, Ontario, and Gatineau, Quebec, Canada. Wetland type did not account for significant variation in principal components based on forest and wetland cover and road density at either spatial extent. Gregarine prevalence was higher in damselflies collected from natural wetlands than in those collected from artificial wetlands and was positively associated with increasing forest cover. In contrast, gregarine intensity was inversely related to road density. Our results suggest that parasitism of damselflies by gregarines is associated with wetland type and landscape characteristics, although the mechanisms producing such relationships are unknown.

Use of Saltmarsh by Dragonflies (Odonata) in the Baie des Chaleurs Region of Quebec and New Brunswick in Late Summer and Autumn

During late summer and autumn, in the Baie des Chaleurs region of Quebec, 18 species of adult dragonflies were recorded during one or more visits of at least 2 hours each to 14 saltmarshes. Three species, Aeshna canadensis, Sympetrum danae and S. internum, were present in more than half of the sites. The most abundant species was S. internum with over 100 seen at some locations. Adults of several species, including Aeshna canadensis, A. umbrosa, Enallagma civile, E. hageni, Ischnura verticalis, Lestes disjunctus, Libellula quadrimaculata, Sympetrum danae, S. internum and S. obtrusum, occurred in relatively high frequencies in both Baie des Chaleurs saltmarshes and in those elsewhere in Acadia. Within Baie des Chaleurs observations of emergence and/or presence of larvae, as well as regional abundance, were recorded for Aeshna canadensis, A. umbrosa, Ischnura verticalis, Sympetrum costiferum, S. internum and S. vicinum. Oviposition in saltmarsh pools was recorded for Aeshna canadensis, Enallagma civile, E, hageni, Ischnura verticalis, Lestes congener and Sympetrum danae. The saltmarsh dragonfly fauna of Baie des Chaleurs is significantly different from that of the rest of Acadia based on frequencies predicted from the latter region. To a large extent this difference is a result of significantly increased use of saltmarsh habitat by adults of six species including Lestes congener, Sympetrum danae, Aeshna canadensis, Sympetrum costiferum, Lestes disjunctus, and Sympetrum internum (in order of decreasing significance) in Baie des Chaleurs in comparison with saltmarshes elsewhere in Acadia. Local amelioration of salty conditions in certain saltmarshes, superimposed on regional amelioration as a result of protection from storms and saltwater dilution in the Baie des Chaleurs estuary, may contribute to an environment where adaptation can occur or where already tolerant species can exist. Dragonflies use saltmarsh habitat on the northeast coast of North America more extensively than is currently documented.

A Potential for the Use of Dragonfly (Odonata) Diversity as a Bioindicator of the Efficiency of Sewage Lagoons

In order to determine whether a relationship existed between water quality and odonate fauna in sewage ponds, data were gathered at each of six ponds of similar construction and equal size and depth in an adjacent series of improving water quality at a lagoon system near Embrun in eastern Ontario. Numbers of nymphs of different species of Odonata were recorded in spring and fall, and similar data was collected on adults in June and July. The data on species presence and abundance for each of three pairs of cells in the sequence was then compared with the corresponding chemical data which included biological oxygen demand, total phophorus, total nitrogen and suspended solids. Water quality improved through the system and species diversity in the final ponds was twice that of the ponds receiving wastewater. Numbers of individuals also increased through the system. Occurrence of Anax junius, Enallagma civile and Ischnura verticalis alone was associated with poorer water quality. Higher diversity including Lestes disjunctus, Leucorrhinia spp. and Erythemis simplicicollis, indicates higher water quality. A potential exists for Odonata species diversity, numbers of individuals and occurrence of particular species to be used as a bioindicator of water quality and a means of evaluating efficiency of a lagoon system. Advantages include data that reflects a time period rather than a point in time and also low costs.

Diet of nymphs affects normal wing development in Ischnura verticalis (Odonata: Coenagrionidae)

Nymphs of many species of the order Odonata are easy to maintain in the laboratory, and there are hundreds of published studies dealing with behaviour, ecology, development, taxonomy, etc. that involve maintenance of nymphs under laboratory conditions. Most of these studies call for nymphs to be fed live prey, and in some cases it is possible to collect suitable prey from the field. However, in cases in which the experimental designs call for controlled diets, or in cases in which natural food is difficult to collect, as during winter months in temperate latitudes, it is common for researchers to feed nymphs with prey cultured in the laboratory. Researchers have used a variety of different prey but Daphnia sp. is one of the most popular. We have used Daphnia sp. cultures but have encountered difficulties in rearing sufficient numbers for use in experiments involving hundreds of nymphs; also, we have had the unfortunate experience of having our cultures collapse for unknown reasons at critical times of experiments.