The complex of species related to Platypalps juvenis Melander is typically northern and montane in distribution, and almost restricted to the Hudsonian and Canadian life zones. They occur from treeline in the Canadian Arctic south to the mountains of New Hampshire on the east, and the mountains of Oregon and Colorado on the west. In this paper, nineteen species are recognized in the complex, of which seven have been described previously.

Entomologists in Canada, especially in recent years, have made an extensive contribution to the study of northern insects. Some 70 field parties of the Northern Insect Survey have worked in almost as many stations in arctic and subarctic Canada and have gathered a great mass of specimens for the Canadian National Collection (Freeman, 1958, 1959). Many taxonomic studies of this material have been published, though almost of necessity they deal with only a small fraction of what is available. Some distinguished studies of the geography of northern insects have likewise been based on these collections, and figured prominently in the symposium on this subject at the International Congress of Entomology at Montreal in 1956. There has also been an extensive program of studies on the ecology and control of the northern biting flies, carried out by the staff of the former Veterinary and Medical Entomology Unit and their collaborators from the Universities. This program also has resulted in publications too numerous for individual mention (Twinn, 1950, 1952, 1955).

The predators of phytophagous mites are being studied at Vineland Station as part of an investigation of the causes underlying the increase of these mites that foIlows the use of DDT and some orher pesticides in peach orchards (Putman and Herne, 1959). Phytoseiid mites, especially Typhlodromus (T.) caudiglans Schuster, are among the commoner predators.

The present work was predominantly stimulated by Moore (1953, 1957) in his studies on the functions of dragonfly territoriality. The objective of this study has been to describe the territorial behavior of Hetaerina americana males and to obtain quantitative information on its function by the capture mark recapture method. Population analyses by marking and recapturing have made possible the calculation of many factors of ecological importance. Flying insects have received especial attention from Dowdeswell, Fisher, and Ford (1940) and Fisher and Ford (1947) for the Lepidoptera and from Jackson (1948) for the tsetse-fly. Borror (1934) was among the first to utilize marking methods for studies on the Odonata. Several investigators have since used such methods for these insects. Corbet (1952) has shown the Odonata to be quite suitable for quantitative study by these methods. Observations on territoriality were made from March to August, 1960, on the San Marcos River, San Marcos, Texas, the San Marcos River, Palmetto State Park, Texas, the San Gabriel River, Georgetown, Texas, and on the Colorado River, 15 miles west of Austin, Texas. The population study was also carried on at the latter habitat in the summer of 1960 from July 4 to August 2 in which 340 individuals were marked and a total of 396 recaptures were recovered.

Over the past ten years a number of exotic predators have been introduced into New Brunswick and other parts of North America as part of a biological control program against the balsam woolly aphid, Adelges piceae (Ratz.). Several of these have become established and others show considerable promise. As introductions continue it becomes exceedingly important that field workers be able to distinguish rapidly all stages of introduced and native predators. Field identification characters for some species (Chamaemyiidae and Syrphidae) have been published in previous papers in this series (Brown and Clark, 1956, 1960; Clark and Brown, 1957) and have been found to be very useful.

Species of the New World genus Stenopterina Macquart (1835, Hist. Nat. Dipt. 2: 453. Senopterina - lapsus) occur mostly in the tropics and subtropics. They are moderately slender metallic blue-green or cupreous flies, up to 12 mm. long with large head and rather long narrow wings, the latter parterncd in various ways with dark brown or black markings. In the type species, Dacus brevipes Fab., 1805 and its closest allies, the wing-pattern consists essentially of three separate areas of infuscation. First, a narrow uninterrupted black costal border extending from the apex of the auxiliary vein to the apex of the fourth. Second, a black streak filling the first basal cell and sometimes invading the cells adjoining it in front and behind. Third, a narrow black cloud on the posterior crossvein. Hendel (1914) in reviewing the genus, considered brevipes a variable species ranging from Texas to Brazil. The recent discovery in British Columbia of a species of Stenopterina with similar wing-pattern has led me to reexamine the status of species placed by Hendel as synonyms of brevipes, particularly Stenopterina caerulescens Lw., 1873, from Texas.

In work on responses of insects to sound at Belleville, by Mr. G. Wishart, a mechanical device was needed to provide a means of slowly revolving a pair of directional light-traps in a horizontal plane on the circumference of a circle 20 feet in diameter. One of the traps was to be used as an experimental trap and the other as a check against the results of the first. A machine was designed, constructed, and put into operation in July, 1961.

The varied interpretations by numerous biologists, of the role of predation in population dynamics have been critically reviewed by Holling (1959) and by Huffaker and Kennett (1956). They conclude that the processes of predation may serve to regulate prey density and disagree with generalizations that minimize the role of predation. This role has been a subject of considerable interest in recent years, notable contributions being the laboratory investigations of Collyer (1958) and Huffaker (1958), and the field studics of Holling (1959).

The ideal method of storing a large collection of insects in liquid should have the attributes of compactness, accessibility to specific vials, minimum servicing, and adequate space for expansion. I tried several methods, each of which failed to meet all of these requirements, before developing a storage system that has proved very satisfactory for an expanding collection of immature stages of bark beetles. Since other workers may also have a similar storage problem, the construction details of the special rack used are shown in Fig. 1, and a brief explanation of other details of the method follows.

Most workers have experienced difficulty at times in producing accurate drawings of microscopic slide images; consequently a number of drawing aids have been invented, none of them entirely successful. The camera lucida, for example, is difficult to use effectively because of the delicate balance necessary between light in the microscope and light on the drawing surface. Also, with this instrument and the many slide projectors, the pencil and hand intercept the projected image. Furthermore with conventional drawing aids, it is difficult to make direct drawings to the scale required for reproduction. It was therefore considered worth while to report on a simple device which appears to overcome these difficulties.