This work, designed to provide an estimate of the quantity of food consumed by spiders, was part of a more general study of the ecology of a spider population in a stand of oaks (Quercus robur L.) in Wytham Wood, Berkshire, England (Turnbull, 1960a, 1960b). Linyphia triangularis (Clerck) was selected as a test spider for the following reasons: it is a common, easily recognized, and easily acquired species; its size closely approximates the mode size of spiders in the population under observation; as far as it may be said of any spider, L. triangularis possesses few specialized features or habits; and the species is amenable to laboratory rearing and manipulation.

A review of insect adaptations for resistance to cold and for life-cycle timing reveals the complexity of the adaptations and their relationships to features of the environment. Cold hardiness is a complex and dynamic state that differs widely among species. Surviving cold depends on habitat choice, relationships with ice and water, and synthesis of a variety of cryoprotectant molecules. Many aspects are time-dependent and are integrated with other factors such as taxonomic affinity, resource availability, natural enemies, and diapause. Timing adaptations reflect the fact that all environments change over many different time frames, from days to thousands of years. Environments differ in severity and in the extent, nature, variability, and predictability of change, as well as in how reliably cues indicate probable conditions in the future. These differences are reflected by a wide range of insect life-cycle systems, life-cycle delays, levels of responsiveness to various environmental signals, genetic systems, and circadian responses. In particular, the degree of environmental change, its predictability on different time frames, and whether it can be monitored effectively dictate the balance between fixed and flexible timing responses. These same environmental features have to be characterized to understand cold hardiness, but this has not yet been done. Therefore, the following key questions must be answered in order to put cold hardiness into the necessary ecological context: How much do conditions change? How consistent is the change? How reliable are environmental signals?

A reinvestigation of the sex pheromone of the eastern spruce bud worm, Choristoneura fumiferana (Clem.), showed that it contains 11-tetradecenal in the ratio 96% trans-: 4% cis-. Field trapping showed the pure trans- compound to be only slightly attractive. Maximum attraction occurred in the range 2% to 5% cis-.

Factors which influence the rate at which Philodromus rufus Walckenaer attacks prey are discussed. Drosophila melanogaster Meign. was used as prey throughout the rearing and testing of P. rufus. Spiders used in these tests were immature at the time of capture and reared to the adult stage in the laboratory. Feeding histories were maintained for all spiders, although the experiments designed to measure the attack response of individual spiders to changing prey density were done with adult males.

In the immature stage there was no difference between the feeding rate of male and female spiders. The adult males, however, were relatively inefficient predators; females killed approximately six times as many flies in their adult lives as males. The irregular feeding pattern of the females, as compared to the fairly uniform feeding pattern of the males, resulted in the males being more amenable to experimental tests. Periods of starvation, molting, and opposition strongly influenced the feeding rate of P. rufus. At high prey densities there was an inverse relationship between hunger and utilization of individual prey. This resulted from uncaptured prey interfering with the feeding spider.

Both feeding time and searching time showed a relationship to prey density. Individual fly activity increased with fly density and this resulted in a functional response curve with an increasing slope. One of the basic requirements for regulation was thereby demonstrated. When prey density was corrected for the increase in fly activity by computing a new density estimate based on fly activity, a typical functional response for invertebrates became evident for hungry spiders but not for well-fed spiders. By using Holling's “disc equation” the difference between starved and satiated spiders was explained as an interaction between prey and predator characteristics. Owing to density-dependent parameters such as prey activity, predator feeding time, and “rate of discovery”, no known mathematical model fitted the data.

The females of many species of chalcids, braconids, pteromalids, and ichneumonids feed on the body fluids or hemolymph of their host. The fact that the adult males do not partake of this food indicates that such feeding may be associated with egg production. Carbohydrate foods, in addition to the body fluids of the host, are essential to egg production in certain species. Feeding on the host by females of certain hymenopterous parasites increases their value as control agents. This feeding sometimes may be more important than parasitism as a cause of host mortality. Itoplectis conquisitor (Say), a host feeding parasite, is considered in this paper.

Ninety-six species of mites were associated with the southern pine beetle and allied scolytids in an outbreak area in Allen Parish, La. The complex was evaluated to ascertain which species may be of value as biological control agents.

Gall inducers are favoured as biocontrol agents of weeds because they tend to have a narrow host range. Six insect and one nematode gall inducer used in Canada are described in terms of their biology, gall morphology, gall physiology, and effectiveness in weed control. The species differ in plant organ attacked, requirement for moisture, whether the galls are induced by secretions or by severing xylem, and effectiveness, which in part relates to the ability of the gall to import nutrients. The most powerful galls divert assimilates from other sinks via a gall’s vascular system joined to that of their host. One of our examples also has mechanisms to compensate for reduction of turgor during drought. Two of the gall inducers enhance their nutrient supply by severing xylem in a plant nutrient sink. One, in the short-term sink of a thistle capitulum, obtains about a quarter of its assimilates at the expense of other capitula. The other, in the long-term sink of a rosette root, approximately halves seed production. Hypotheses are presented to explain various aspects of gall development and function.

The first part of this paper discusses the characteristics of the arctic environment as it influences insect life. The most important features are the low temperature, the low annual heat budget, the severe and often variable weather and the continuous daylight of the growing season. A certain uniformity in aspect of the tundra environment is mentioned. Some microclimatic and regional differences are considered and a definition of the low arctic life zone is proposed.

The make-up of the arctic fauna is considered in the second section. In the low arctic there may be up to 5% of the number of species found in a comparable temperate area, and in the Queen Elizabeth Islands about 1%; but the representation of the various groups of insects in the arctic varies greatly, the Diptera, and especially the Chironomidae, being by far the most numerous. The fauna is derived from that of the north temperate zones, by extensive reduction and by a limited development of endemic forms up to, but rarely beyond, the specific level. Many of the endemic forms seem to be adaptations to the special features of the environment, especially the low temperature and short season; while others appear to show a loss of specialized features, e.g. of colour or pattern, in relation to the small number of species in their environment and the consequent lower level of biotic interactions. The arctic Lepidoptera are frequently cited in these sections and a number of species are figured.

The paper concludes with a discussion of the general reasons why so few species are found in the arctic. The arctic environment is not inherently simple and does not forbid a greater diversity, yet in fact very few species occur. It seems to lie beyond the range of physiological tolerance of all but a very few of the forms of temperate origin. But, given time, there is no apparent reason why a greater diversity should not develop, although the evolutionary process is probably slower in the arctic and is always liable to be set back by climatic disasters, from the last of which the fauna has only just begun to recover. It is suggested however that the arctic will always tend to lie towards the limit of the physiologically possible range because in fact the greatest continuity of evolutionary history has been in the tropics and most forms of life have thus been shaped in response to tropical conditions.

Inoculative freezing of insects is distinguished from nucleative freezing and is treated from the standpoint of the delays observed in freezing. On the assumption that the fine structure of the cuticle regulates the penetration or growth of external ice into the insect's body, the cuticle was experimentally altered by soaking, boiling, and immersion in strong detergent solution. Soaking was of doubtful effectiveness, whereas boiling and detergent hastened inoculation, Detergent also caused many insects to freeze when the contact water froze, with no delay. Rate of inoculation of untreated larvae was directly proportional to the area in contact with ice, and inversely proportional to temperature down to −10 °C. No further rate increase took place down to −15 °C, possibly because the vapor pressure difference between ice and supercooled body fluid does not change appreciably in this temperature range. Larvae froze more rapidly when they had already been frozen and thawed once or twice. No relation between inoculation rate and rate of water loss in a dry atmosphere could be established.

The freezing of water in extremely small spaces is discussed and related to the process of inoculative freezing. Probable pathways of ice growth through the cuticle are considered in relation to known structural characteristics and the results of the present experiments. Two hypotheses are proposed to account for the observed delays in freezing, but neither is wholly satisfactory. The first postulates that the outer extremities of the pathways, through the epicuticle, are hydrophobic and contain air which temporarily separates contact moisture from pore liquids. After freezing of the contact moisture a vapor pressure differential results in a net flow of vapor outwards, the vapor freezing on the ice and building inwards until the ice front touches liquid in a space large enough to allow freezing. This hypothesis assumes the existence of at least one pathway large enough to support ice penetration without hindrance caused by restricted size. The second hypothesis assumes that no such unrestricted pathways are present, all being inadequate in size. Differences in chemical potential between ice and liquid cause pore liquids to move outwards to the contacting ice surface and accrete on its

When Wyatt and Kalf (in press) reported the presence of glycerol in the haemolymph of Hyalophora cecropia (L.) pupae, the possibility that it was responsible for the ability of this stage to survive freezing was naturally raised. It is well known that glycerol may protect animal tissues from injuries otherwise caused by ice formation. Many other substances have a degree of similar protective ability but are less effective for various reasons. Lovelock (1954) tested the protective action of 15 neutral solutes on human red blood cells and found glycerol to be almost ideal because of its high solubility in aqueous salt solutions, its ability to permeate the cell rapidly and completely, its low molecular weight, and its absence of toxicity even when in great excess.

Courtship displays of empidine dance flies (Diptera: Empididae), which include transfers of nuptial gifts during mating, are reviewed in light of sexual selection theory. Sex-role reversed courtship behavior, involving female swarming and male choice, appears to be correlated with certain female secondary sexual characters that are widespread throughout the Empidinae. The tendency to shift mate choice from females to males, and the apparent development of autogeny in many empidine species, are both hypothesized to have resulted from males monopolizing the proteinaceous food source of non-hunting females, through transfers of nuptial gifts of prey. The autogenous condition appears to have led to the ritualized presentation of various types of inedible nuptial gifts by males of several species, possibly including the development of secreted nuptial gifts, or balloons, as displays of male fitness.

Reciprocal field tests of attraction between populations of Ips pini (Say) from California, Idaho, and New York disclosed geographic variation in pheromone systems. These differences reside both in pheromone production and reception. However, it is unknown whether variation in the pheromone bouquets is qualitative, quantitative, or both.

In New York, both sexes responded in higher numbers to their own pheromone than that produced by California or Idaho males. In California, beetles of both sexes discriminated against New York, but in Idaho only females made this distinction. In both California and Idaho, the local population showed a slight preference for the pheromone produced by Idaho males over that produced by California males.

The predator Enoclerus lecontei (Wolc.) demonstrated a four-fold preference for attractants produced by males from New York over those produced by beetles from California and Idaho. The parasitoid Tomicobia tibialis Ashmead showed the opposite trend.

There is no evidence that geographic variation in the pheromones produced by I. pini is sufficient to enforce breeding isolation between adjacent populations. However, these results dramatize the necessity of considering pheromonal variability in programs applying pheromones for the survey and control of widely distributed pests.

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is historically one of the most important economic insect pests in the northern Great Plains of North America. Within this geographical region, the areas subjected to greatest attack are southern Alberta and Saskatchewan, southwestern Manitoba, eastern and northern Montana, North Dakota, northern South Dakota, and western Minnesota. Cumulative grain-yield losses and annual economic losses associated with this pest can exceed 30% and $350 million, respectively. Solid-stemmed cultivars of common wheat, Triticum aestivum L. (Poaceae), tolerant of infestation, are critical for C. cinctus management, but outbreaks of this pest continue to occur even after six decades of cultivar development. Furthermore, chemical control (a primary control option for other cereal (Poaceae) insect pests) has proven ineffective; this underscores the need to integrate resistant cultivars into a comprehensive integrated pest management program. We provide overviews of wheat stem sawfly biology, recent advances in applied research, the efficacy and integration of cultural and biological management strategies, and future directions for global research activities to manage wheat stem sawfly.

For over three decades, the importance of taxon sampling curves for comparative biodiversity studies has been repeatedly stated. However, many entomologists (both within Canada and worldwide) continue to publish studies without standardizing their data to take sampling effort into account. We present a case study to illustrate the importance of such standardization, using the collection of spiders (Araneae) by pitfall traps as model data. Data were analyzed using rarefaction to represent one example of a taxon sampling curve, and by a variety of traditional diversity indices to describe alpha diversity. Raw species richness and single-index diversity measures (Shannon–Wiener, Simpson's, and Fisher's α) provided contradictory results. Rarefied species richness standardized to the number of individuals collected enabled more accurate comparisons of diversity and revealed when sampling was insufficient. Focusing on arthropods occurring in forested ecosystems, we also examined the use of taxon sampling curves in current literature by reviewing 133 published articles from 14 journals. Only 26% of the published articles in our review used a taxon sampling curve, and raw species richness and the Shannon–Wiener index of diversity were the most commonly used estimates. There is clearly a need to modify how alpha diversity is measured and compared for arthropod biodiversity studies. We recommend the abandonment of both raw species richness and single-index measures of diversity, and reiterate the need to use rarefaction or a related technique that allows for meaningful comparisons of species richness while taking into account sampling effort.

Studies were made on the distribution and survival of the mountain pine beetle over the lower stem of lodgepole pine. The relationship between density of attack and subsequent total length of egg galleries was examined as was the relationship between number of exit holes and number of emerging beetles. The influence on brood survival of tree diameter, density of egg galleries, moisture content of the outer sapwood, lethal temperatures, resinosis in the subcortical region, predators, and parasites is described. Survival is compared between broods established during different flights in the same year. The optimum weather conditions for brood survival are discussed.

In cold climates most aquatic habitats are frozen for many months. Nevertheless, even in such regions the conditions in different types of habitat, in different parts of one habitat, and from one year to the next can vary considerably; some water bodies even allow winter growth. Winter cold and ice provide challenges for aquatic insects, but so do high spring flows, short, cool summers, and unpredictable conditions. General adaptations to cope with these constraints, depending on species and habitat, include the use of widely available foods, increased food range, prolonged development (including development lasting more than one year per generation), programmed life cycles with diapause and other responses to environmental cues (often enforcing strict univoltinism), and staggered development. Winter conditions may be anticipated not only by diapause and related responses but also by movement for the winter to terrestrial habitats, to less severe aquatic habitats, or to different parts of the same habitat, and by construction of shelters. Winter itself is met by various types of cold hardiness, including tolerance of freezing in at least some species, especially chironomid midges, and supercooling even when surrounded by ice in others. Special cocoons provide protection in some species. A few species move during winter or resist anoxia beneath ice. Spring challenges of high flows and ice scour may be withstood or avoided by wintering in less severe habitats, penetrating the substrate, or delaying activity until after peak flow. However, where possible species emerge early in the spring to compensate for the shortness of the summer season, a trait enhanced (at least in some lentic habitats) by choosing overwintering sites that warm up first in spring. Relatively low summer temperatures are offset by development at low temperatures, by selection of warm habitats and microhabitats, and in adults by thermoregulation and modified mating activity. Notwithstanding the many abiotic constraints in cold climates, aquatic communities are relatively diverse, though dominated by taxa that combine traits such as cold adaptation with use of the habitats and foods that are most widely available and most favourable. Consequently, except in the most severe habitats, food chains and community structure are complex even at high latitudes and elevations, including many links between aquatic and terrestrial habitats. Despite the complex involvement of aquatic insects in these cold-climate ecosystems, we know relatively little about the physiological and biochemical basis of their cold hardiness and its relationship to habitat conditions, especially compared with information about terrestrial species from the same regions.

Losses in yield of spring wheat due to infestations of Sitodiplosis mosellana (Géhin) were determined for 700 000 ha of arable land in northeast Saskatchewan, Canada in 1983. The proportion of kernels infested (y) was a power function of the number of wheat-midge larvae (x) (y = 35.3x0.725). One, 2, 3, and 4 larvae per kernel resulted in a level of infestation of 38, 58, 78, and 96%, respectively. There was no significant difference between infestation levels from fields sampled at the heading stage of crop growth and the estimates of infestation levels for these fields at harvest time. Yield of grain (y) was negatively exponential to an increase in level of infestation (x) (ln y = 5.7−0.017x). Infestations of 30, 60, and 90% reduced yields of spring wheat by 40, 65, and 79%, respectively. The average decrease in crop yield in the study area was about 30%, which resulted in estimated losses in total gross revenue of about $30 million.

The importance of the mountain pine beetle to the pine forests of North America has been pointed out by several writers (Hopkins, 1909; Swaine, 1918; Evenden et al., 1943; Hopping and Mathers, 1945). Its range covers parts of southern British Columbia and Alberta, Idaho, Montana, Wyoming, Oregon, Washington, California, Utah, and Nevada. The size of populations and the damage vary from year to year. A study of the biology of the mountain pine beetle was made by the writer from 1955 to 1960 in several small outbreak areas near Invermere, British Columbia. (50°30′ N. lat., 116°00′ W. long., 2740 feet above sea level). The host tree in these areas was lodgepole pine, Pinus contorta Douglas var. latifolia Engelmann. The results of the study will be presented in three parts. Part I is presented herein and describes the life cycle, brood development, and flight periods. Part II is a discussion of the behaviour of the adult as affected by physical factors operating under the bark. Part III describes the interaction of the insect and its host, with special reference to mortality and brood survival.

Mathematical discussions of models of functional response (predation rate as a function of prey density) have usually emphasized description of the shape of the functional-response curve. However, lack of congruence between experimental design and data analysis and under-utilization of appropriate statistical methods of analysis have hindered an empirical synthetic treatment of such feeding behavior. Here we review existing experimental and statistical procedures with reference to Holling's generalized model of functional response, and describe: (1) an experimental design compatible with the assumptions of the model; (2) a maximum-likelihood method for fitting the model; (3) several methods for statistical comparison of sets of functional-response curves; and (4) an exploratory graphical method for examining patterns of variation among larger numbers of samples.

Colonies of P. fuscatus that were initiated by various numbers of foundresses were studied to gather basic life table information. This information was used to estimate the selective advantage of foundress association according to a kin selection model, a parental manipulation model, two individual selection models, and a combined kin and individual selection model. Life table data were obtained for colonies located in exposed nest sites and for colonies located in nest sites provided with protection from vertebrate predators. Relative productivity of colonies produced by different size foundress associations and under different levels of predation pressure were determined. Multiple foundress colonies were found to be more productive and have an increased ability to re-establish after an episode of predation when compared with single foundress colonies. When predation levels on the colonies were high, multiple foundress colonies were more productive per colony and per foundress. When predation levels on the colonies were low, multiple foundress colonies were more productive per colony but less productive per foundress. At high levels of predation, when the queens and joiners were all assumed to have equivalent potential productivities, the kin selection model, the parental manipulation model, and the combined kin and individual selection model all predicted a selective advantage for joiners in foundress associations. At low levels of predation, when the wasps are assumed to have equivalent productivities, only the parental manipulation model predicted a selective advantage for joiners in foundress associations. When the assumption of equivalent potential is relaxed and when the wasps are assumed to be capable of detecting and acting upon individual differences in productivity, then all of the models could account for the existence of foundress associations. However, under this last set of assumptions the individual selection models require that the joiners have very low potential productivities.