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.

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.

Although the structure of the ovipositor of parasitic Hymenoptera is largely uniform, interspecific variation in its morphology can be observed. Such variability may be related to the diversity of hosts attacked. To verify such an hypothesis, we compared, using correspondence analysis, the morphological characteristics of the ovipositors of 20 species in three categories: (i) species belonging to the same taxonomic unit and attacking the same type of host, (ii) species belonging to the same taxonomic unit but attacking different types of host, and (iii) species belonging to different taxonomic units but attacking the same type of host. Results show that variability in some morphological traits of the ovipositor can be related to host characteristics. Adaptive convergence in morphological variations observed between species is discussed.

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.

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.

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).

We review the existing literature on patterns of moth (Lepidoptera) species richness and community composition in northeastern Nearctic forest ecosystems across hierarchical scales ranging from individual trees to entire managed ecoregions. Moths are species-rich in northeastern forests of North America, with the most diverse families being Noctuidae and Geometridae. Individual trees and forest stands, however, are often dominated by few species. Climate, stand age, disturbance regime, and landscape heterogeneity are significant predictors of abundance of dominant species. Most other moth species in the regional pool are patchily distributed and appear to occur regularly at very low abundance. Moth communities respond predictably to forest-management practices, and the outcomes of postmanagement response are largely driven by changes in the plant community. Significant reductions in moth species richness and changes in community composition are correlated with clear-cut harvesting, whereas selective logging appears to cause more moderate changes in moth community structure. Broad-scale effects of forest fragmentation on moth communities in unglaciated regions are best described by species replacement rather than species loss; moth species richness decreases slightly across a gradient of fragment sizes, but shifts in moth community composition are more important, especially in the relative importance of herbaceous-plant-feeding species in large and small fragments. Species that appear to be most sensitive to timber management or habitat loss are dietary specialists as larvae, dispersal-limited as adults, or dependent on commercially valuable tree species such as oaks, Quercus L. (Fagaceae). Restored forest stands tend to converge in terms of lepidopteran species dominance and diversity among stands, suggesting that the long-term consequences of timber management or habitat loss include a significant reduction of regional β-diversity. Finally, future research on forest Lepidoptera should include an emphasis on understanding the role of urban woodland habitat in retaining viable and diverse moth communities and how the spatial pattern of timber harvest affects the relative magnitude of α- and β-diversity components within a given ecoregion.

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.

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.

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.

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.

Populations of two abundant coccinellid species, Coleomegilla maculata lengi Timberlake and Hippodamia tredecimpunctata tibialis Say, responded rapidly to corn leaf aphid populations [Rhopalosiphum maidis (Fitch)] once the aphids became exposed to predation when the plants tasselled. Coleomegilla m. lengi oviposited at lower densities of aphids than did H. t. tibialis but H. t. tibialis was shown to have a greater numerical response than C. m. lengi at high densities of aphids due to its greater fecundity. The numerical response of the coccinellids by oviposition was linear with a lag of 1/2 week behind the aphid population.

This paper deals with the orientation reactions exhibited by larvae and adults of the spruce budworm, Choristoneura fumiferana (Clemens), (12) in response to stimulation by light. The insect is an important pest of the coniferous trees, Abies balsamea Mill, and Picea spp., which compromise the pulpwood stands of the forests of northeastern North America. Hence, at present, it is the subject of many investigations. The work reported here is part of an investigation designed to provide data for the development of studies of the effects of weather and climate upon the spruce budworm.

Studies on the biology of Encarsia pergandiella Howard, a solitary, arrhenotokous endoparasite, revealed that fertilized eggs, which give rise to females, are deposited in whitefly nymphs preferably in second, third or fourth instar, while unfertilized eggs, which give rise to males, are deposited in Encarsia larvae at whose expense they develop. The parasite adults were observed to feed on body fluids of whitefly nymphs. Both sexes have a pupal and three larval stages, and development from egg to adult at approximately 75° F. takes 15 days for the females and 13 to 14 days for the males. Mean longevity of the females at constant and fluctuating temperatures was studied. Actual mean fecundity at 75 ± 4° F. was 48.5 eggs per female, all of which were deposited during the first 70% of her life, provided hosts were abundant. Field observations revealed that E. pergandiella was present throughout the year, reaching highest numbers in the spring and summer. The parasite does not have an obligatory period of dormancy for all of its individuals. E. pergandiella was not able to prevent whiteflies from causing heavy damage to plants. The reason may be in the discrepancy between the rate of increase of the whitefly and the parasite.

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.

The larvae of the European pine shoot moth, Rhyacionia buoliana (Schiff.), feed on several species of hard pines, of which the most economically important are red pine, Pinus resinosa Ait., and Scots pine, Pinus sylvestris L. Approximately one hundred million trees of each species mere planted in southern Ontario since 1905, most of them since 1925. Many pure and mixed stands are now infested by R. buoliana which has no apparent preference for either host tree.

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.

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.

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.

Field, glasshouse, and laboratory tests showed that deposits of polyhedra of the nuclear polyhedrosis virus of the cabbage looper, Trichoplusia ni (Hübner), on foliage are practically non-infective after a 1-month exposure to weathering. Inactivation by sunlight appeared to be more important than removal by washing by rain in causing this loss of activity. The virus was readily inactivated by exposure to ultraviolet light. Virus exposed in aqueous suspensions of polyhedra or in wetted deposits was inactivated by shorter exposures than was virus in dry deposits of polyhedra.