Comparatively few laboratory-caged apple maggot flies, Rhagoletis pomonella (Walsh), of either sex arrived at the site of assembly for mating (ceresin wax oviposition domes) and no mating pair or ovipositing females were observed until the flies were 7–8 days old. From then on, the level of all three of these activities progressively increased.With respect to the time of day of activity, in the field, assembly of both sexes of flies on the fruit, mating, and oviposition all occurred predominantly during the afternoon on a day when the sun shone brightly throughout the 15-hr daylight period and the ambient temperature was 16 °C at dawn, 24.8° in mid-afternoon, and 17.5° at dusk. Little or no activities of these sorts occurred before mid-morning and toward dusk. In the laboratory, where light intensity was constant at 1000 lux during the 15-hr photophase, the temporal pattern of these activities was the same as in the field when laboratory temperature was programmed to be the same as in the field for the corresponding hour of daylight. However, when laboratory temperature was programmed to be constant at 24.8°, these activities occurred at a high rate throughout the photophase. None of these activities was observed to have been initiated in darkness. It is concluded that sexually mature apple maggot flies may assemble on the fruit, mate, and oviposit whenever temperature is favorable and light intensity is sufficient to permit adequate vision.

Biologists in general, and entomologists in particular, have published many data of the ‘percentage mortality’ type. It appears to be a natural tendency in the ecological study of an insect to attempt to measure the degree of mortality caused bv difierent factors. Early publications listed many figures on ‘percentage age parasitism’ because it was one of the easiest mortalities to measure. More recently, as betrcr techniques were developed for population sampling and mortality assessment, it has been possible to derive mortality data for other factors. Notable progress has even been made with such difficult problems as measuring the mortality caused by avian, mammalian, and invertebrate predators. Despite these developments, life tables generally show some residual mortality that cannot be attributed to a specific factor. Frequent population measurement can establish the exact time of such mortality, however, while concomitant work on behaviour, physical ecology, and inherent factors can provide very useful clues as to what intrinsic or extrinsic factors it may be related. Fairly complete life tables are already available for natural populations of a few species, and will no doubt become available for additional species from time to time.

The two-spotted spider mite, Tetranychus telarius (L.), is a well known pest of many plants in greenhouses. It is notoriously difficult to conarol, especially when resistant populations develop, and usually requires frequent acaricidal treatment during the growing season. Biological control has sometimes been suggested in view of the success that was achieved by this method against other greenhouse pests and because the environment is controllable to some extent, but only a few attempts have been made.

The solitary aphid parasitoid Ephedrus californicus Baker is able to discriminate between unparasitized and parasitized third-instar nymphs of the pea aphid, Acyrthosiphon pisum (Harris). Superparasitism varied with the number of mature eggs (which is age-dependent) present in the ovaries as well as with the number and the quality of any hosts encountered. Conspecific superparasitism varied with wasp age; older females, with a large egg supply, accepted hosts parasitized by a conspecific female if unparasitized aphids were unavailable. Self superparasitism occurred at all ages; it was the least likely behaviour compared with egg deposition in unparasitized and conspecific-parasitized hosts. Prior experience (learning) was not necessary for host discrimination, but it did influence the search rate, which was higher in inexperienced than experienced females. In choice experiments, wasps preferred conspecific- over self-parasitized aphids and thus were able to distinguish between them. It is suggested that oviposition markers vary among conspecific females. The data are discussed with reference to theories about oviposition decisions and progeny allocation in solitary hymenopteran parasitoids.

New spruce beetle, Dendroctonus rufipennis (Kirby), adults of univoltine and semivoltine life cycles, as well as re-emerged parent beetles, were laboratory-tested for differences in reproductive capacity and brood characteristics. Parameters measured from the three groups include dry weight, lipid content, and egg production. Brood characteristics measured include egg length, development rates, and survival densities. Although there were some differences in dry weight and lipid content, females from the univoltine, semivoltine, and re-emerged parent groups did not greatly differ in egg production. Egg length was slightly smaller for eggs from univoltine parents, but other measured brood characteristics did not differ among the three parent groups, including the density of the surviving brood. In a field study, re-emerged parent beetles were determined to be flight capable. These findings imply that populations with univoltine broods will have higher growth rates than semivoltine populations. Consequently, the presence of univoltine broods, which is weather dependent, increases the risk of a beetle outbreak or can accelerate the rate of spruce mortality in an established outbreak. These results also indicate that re-emerged parent beetles can contribute substantially to brood production. Suppression strategies can be more effective if managers consider the ecological consequences of brood production from the three parent groups.

Experiments were carried out to determine the functional response of Podisus modestus (Dallas) to densities of two colonial species of jack pine sawfly, Neodiprion swainei (Middleton) and N. pratti banksianae (Rohwer). Two types of functional response curve were exhibited by the pentatomids, a domed response curve and a negatively accelerated curve.The domed response was caused by the more effective defense reactions of the sawfly larvae at higher densities.An equation is proposed for the domed response curve. The implications of the domed functional response are discussed in relation to the social behavior of these sawflies.

The hemlock looper, Lambdina fiscellaria fiscellaria (Guen.), has been an important forest pest in Newfoundland for many years. Outbreaks have been reported from widely separated parts of the Island and in most cases the mortality of balsam fir, Abies balsamea (L.) Mill, has been high.

An investigation of the biology of the insect was commenced in 1950 at Lake St. George where two separate infestations had appeared in 1949. These infestations died out in 1951 and only limited information was obtained on some aspects of the investigation. As there is little prospect of continuing field studies in the near future, the results to date are being reported.

In 1951 to 1955 Mr. N. H. Anderson of the Belleville laboratory, and Mr. C. V. G. Morgan, Entomology Laboratory, Summerland, B.C., collected plant material in southern British Columbia to investigate the distribution there of phytoseiid mites. Many phytoseiids in this material were apparently undescribed, and in 1956 the author collected further specimens. Nine undescribed forms were found; descriptions of these are given below, with a key for identifying the adult females of all phytoseiid species known to occur in British Columbia. The new species all are of the genus Typhlodromus Scheuten, 1957, as defined by Chant (in preparation). The mites were cleared in chloral hydrate or lactic acid and mointed in Berlese's fluid; but some were mounted directly in De Faure's fluid. The measurements given are of the greatest lengths and widths of the dorsal and ventri-anal shields, and whenever possible are the means for 10 specimens. The setal terminology of Garman (1948) and Nesbitt (1951) is followed. All specimens referred to were collected in British Columbia unless otherwise stated.

Saproxylic insect assemblages inhabiting dead wood in Canadian forests are highly diverse and variable but quite poorly understood. Adequate assessment of these assemblages poses significant challenges with respect to sampling, taxonomy, and analysis. Their assessment is nonetheless critical to attaining the broad goals of sustainable forest management because such species are disproportionately threatened elsewhere by the reductions in dead wood generally associated with commercial exploitation of northern forests. The composition of the saproxylic fauna is influenced by many factors, including tree species, degree of decay, stand age, and cause of tree death. Wildfire and forest harvesting have differential impacts on saproxylic insect assemblages and on their recovery in postdisturbance stands. Exploration of saproxylic insect responses to variable retention harvesting and experimental burns is contributing to the development of prescriptions for conserving saproxylic insects in boreal forests. Understanding of processes that determine diversity patterns and responses of saproxylic insects would benefit from increased attention to natural history. Such work should aim to provide a habitat-classification system for dead wood to better identify habitats (and associated species) at risk as a result of forest management. This tool could also be used to improve strategies to better maintain saproxylic organisms and their central nutrient-cycling functions in managed forests.

Experiments were designed to find the functional response (response per predator) of the pentatomid Podisus maculiventris to the population density of larvae of the fall webworm, Hyphantria cunea. The response was measured in confined universes, (glass jars), representing webworm nests, and it was found permissible to vary universe size, within certain limits, in order to obtain a wide range of prey densities without handling large numbers of larvae. The “disc equation” proposed by Holling (1959) was found to describe the response curves, except at very high prey densities, and to provide a satisfactory biological explanation for their decreasing slopes. P. maculiventris ingests about 84% of its own weight for each fifth-instar larva of H. cunea attacked successfully, and the time spent in feeding and becoming hungry enough to make another attack reduces very substantially the time devoted to searching activities. Both prey defense (Fig. 1) and the age of the adult predator (Fig. 2) have very important effects on the functional response curves and on the values of the parameters, a and b, of the disc equation. These effects are explained. The “rate of discovery”, a, is contrasted to Nicholson's (1933) “area of discovery” and it is shown why the former is more likely to be independent of prey density than the latter.

In view of the population of webworm larvae in the average nest, it is concluded that the functional response of the various predators inside the nest is probably not important, and that attention should be devoted instead to the functional and numerical responses of predators and parasites to the density of nests per unit area. Because of the vigorous defense exhibited by fifth-instar webworm larvae, predation by timid predators like P. maculiventris is selective and larvae whose development is delayed by parasitism are likely to suffer more predation than healthy larvae.

We provide keys for identifying the 26 bumble bee species (Bombus and Psithyrus) found in Canada east of Manitoba, and information on their ecology and distribution. The keys are designed for field use and rely primarily on colour patterns rather than on microscopic features.

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).

Natural control factors are normally relied on to hold destructive insects below the level of economic damage. When insect control is attempted every effort should be made to prevent injury to beneficial parasites and predators.

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, is an important enemy of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. Present control practices for the Douglas-fir beetle consist of rapid cutting, transportation, and milling of infested trees so that beetles will be destroyed in the slabs before they emerge to infest other trees. During these operations, natural control agents are often inadvertently destroyed along with the beetles. Because of this fact serious beetle infestations may be unnecessarily prolonged. Detailed knowledge of the life history of the narural control agents and of the effect of logging and milling practices on the populations of beneficial parasites and predators is needed before control practice recommendations, which may be less destructive to the beneficial insects, can be set forth.

Urbanization causes the fragmentation of natural habitats into isolated patches surrounded by anthropogenic habitats. Fragment size and the intensity of human disturbance have been shown to affect both composition and diversity of arthropod communities, but most groups have been understudied. We investigated effects of urbanization on ant assemblages (Hymenoptera: Formicidae) in and around the Molson Reserve, a preserved maple-beech forest surrounded by residential properties near Montréal, Quebec. We studied how local ant assemblages differed in terms of composition, abundance, and species richness, depending on whether they were situated in the interior forest, in adjacent residential backyards, or at the edge between these two habitats. We also compared an intact forest interior with a younger and moderately disturbed forest (“buffer zone”) between the urban matrix and the interior forest. Few differences were detected between the buffer zone and the intact forest interior. Extrapolated estimates of species richness suggest that it is lowest in the forest interior and highest in urban zones. Community composition, as investigated with ordination analysis, revealed a clear difference between the fauna of urban sites and the fauna of edges and forest interiors, and analyzing the relative abundance of ants showed residential backyards to contain the most ants. Urban assemblages were characterized by several competitively dominant species, including one introduced or “tramp” species. The occurrence of aggressive and dominant species in urban sites and at the edges of the Molson Reserve could potentially interfere with the dispersal and immigration of ground-dwelling arthropods and negatively affect local diversity or community composition in isolated forest reserves in urban centres.

It has long been known to collectors of Coleoptera that European species unknown to other parts of North America may be taken in the Maritime Provinces of eastern Canada. Some of these species are abundant, and virtually all who have collected in the region have had some experience with them. The region of the Lower St. Lawrence and adjacent parts of the Province of Quebec have also supplied the first North American records of a number of European species. Because these species are of some special interest, I have compiled the list given below.

Extensive collections of synanthropic fly parasitoids in animal excrement accumulations in the United States, Mexico, Costa Rica, Puerto Rico, Uruguay, Chile, Denmark, Israel, and South Africa yielded seven forms of a Muscidifurax complex which were totally or partially reproductively isolated. Morphological studies of female and male parasitoids coupled with biological and zoogeographical information permitted the identification of five sibling species. Muscidifurax raptor Girault and Sanders 1910 is redescribed and four additional species are described as new: M. zaraptor, from the southwestern United States; M. raptoroides from Central America and Mexico; M. uniraptor from Puerto Rico, and M. raptorellus from Uruguay and Chile. Biological notes are added to the descriptions, and it was postulated that the genus is undergoing a process of speciation with local populations slowly becoming reproductively isolated and eventually giving rise to morphologically distinguishable entities. Most evidence suggests the establishment of Muscidifurax in the New World, concomitant with or shortly following the establishment of muscoid flies in accumulated excrement. Scanning electronmicroscopy was used in the analysis of some morphological structures.

The commercial production of apples has led growers to greater reliance on chemical control measures for pests than have most fields of agricultural production. Since the turn of the century orchardists have plunged deeper and deeper into artificial measures to produce fruit free from blemishes without greatly alleviating the over-all pest problem and, in some cases, actually producing conditions conducive to still greater problems.

Arctic arthropods are essential prey for many vertebrates, including birds, but arthropod populations and phenology are susceptible to climate change. The objective of this research was to model the relationship between seasonal changes in arthropod abundance and weather variables using data from a collaborative pan-Canadian (Southampton, Herschel, Bylot, and Ellesmere Islands) study on terrestrial arthropods. Arthropods were captured with passive traps that provided a combined measure of abundance and activity (a proxy for arthropod availability to foraging birds). We found that 70% of the deviance in daily arthropod availability was explained by three temperature covariates: mean daily temperature, thaw degree-day, and thaw degree-day2. Models had an adjusted R2 of 0.29–0.95 with an average among sites and arthropod families of 0.67. This indicates a moderate to strong fit to the raw data. The models for arthropod families with synchronous emergence, such as Tipulidae (Diptera), had a better fit (average adjusted R2 of 0.80) than less synchronous taxa, such as Araneae (R2 = 0.60). Arthropod abundance was typically higher in wet than in mesic habitats. Our models will serve as tools for researchers who want to correlate insectivorous bird breeding data to arthropod availability in the Canadian Arctic.

Detailed laboratory studies of mated spruce budworm (Choristoneura fumiferana (Clem.)) show that the number of eggs per day, mean cluster size, and mean wet weight of the eggs gradually decrease during the period of oviposition of individual moths. The term mean weight of initial eggs (Ei) is defined and compared with other measurements of mean egg weight based on total egg complement or parts of it. Ei is 6%–12% greater than the mean egg weight based on all eggs laid. In spite of variation in pattern of egg weight distribution among moths, Ei appears to express satisfactorily the differences in mean egg weight among moths and can be used to survey egg weights among populations.

Laboratory rearing studies of individual clusters indicate slightly slower emergence rates (seconds from hibernacula), greater survival, and smaller proportions of male pupae in the third and fourth quartiles of the egg complement; there were no differences in pupal weights related to cluster order. There is no ready explanation for this improved survival of larvae from eggs known to be smaller.

Implications of these results for the population dynamics of the spruce budworm are discussed. The more stressful conditions encountered in the natural environment may counteract the apparently better survival of individuals from the latter part of the egg complement.

Body size and mass variation of queen bumble bees (Bombus Latr. spp.) were analyzed in relationship to hibernation survival and optimal body size. Body mass and size (measured by radial cell length) were significantly correlated in six of eight species. Also, spring queens of B. occidentalis Greene were, on average, significantly larger yet lighter than young fall queens. These observations were consistent with weight loss known to occur during hibernation coupled with greater mortality of small queens over the winter. Thus large queens may be at an advantage for this and other reasons (e.g. foraging efficiency, usurpation). However, an optimality model showed that an intermediate body size was optimal if the reproductive success of a colony (foundress queen and workers) was considered. The assumptions were that fitness did not increase linearly with body size but was a convex function, and that colonies only had a fixed amount of energy to invest in reproductive offspring leading to a trade-off between size and number.