An energy-flow multitrophic-level model incorporating acquisition (functional response) and assimilation (metabolic pool model) functions and stochastic development is proposed and put into historical perspective. The model is general for each trophic level and for all subcomponents. Prey demand drives the functional response model, while food supply–demand determines all intrinsic rates in the model. The model is used to explore the theoretical properties of a multitrophic system comprising alfalfa, blue aphids, pea aphids, a host-specific parasitoid, and two predators (lady beetles, green lacewings). The model shows:

(1) the importance of the resource base on higher trophic level dynamics and vice versa

(2) the stability properties of different combinations of species

(3) the role of parasitoids and predators in population regulation in this system

(4) how food acquisition and respiration as functions of temperature and per capita resource interact to determine the rate of population growth

(5) that extreme caution must be used in extrapolating theoretical results to field situations.

The relationship between the temperature and the speed of development is described for the Kamloops ‘biotype’ of the pea aphid, Acyrthosiphon pisum, and some of its associated hymenopterous parasites. The primary parasites are: Aphidius ervi ervi, A. ervi pulcher, A. smithi, and Praon pequodorum; and the secondary parasites are: Asaphes lucens and Dendrocerus niger. For each species the lower temperature threshold for development and the time-to-adult was determined under constant laboratory conditions using field-grown alfalfa as a host plant for the pea aphid and the first-generation offspring of field-collected aphids and parasites. The thermal constants enable the prediction of aphid and parasite population growth, as influenced by temperature, on a physiological time-scale.

Prepupae of Neodiprion sertifer (Geoff.) held in darkness at 21 °C undergo a short normal diapause if exposed as feeding larvae to long photoperiods, but have no diapause if reared in the larval stage under short photoperiods. If cocoons from short-day rearings are exposed to 10 °C instead of 21 °C, a small proportion of the prepupal larvae undergo the normal or short diapause, but the majority enter an intense or prolonged type of diapause which results in three clearly defined periods of adult emergence within the range of 160 to 800 days after cocoon spinning. Mortality increases directly with the prolonged cocoon periods associated with intense diapause at 10 °C and there is a progressive decrease in reproductive potential of the survivors. If cocoons are held at 29 °C normal diapause and morphogenesis are prolonged but there is no evidence that a state of intense diapause is induced. Mortality is extreme, however, and the reproductive potential of the survivors is greatly reduced.

The implication of these findings is discussed in relation to prolonged diapause in nature, a factor critical to the assessment of the seasonal history and population dynamics of the insect.

Entomologists interested in population dynamics have devoted considerable attention to the numbers of eggs laid by various species of insects, the mortality and non-viability of eggs, and mortality in young larvae; but there is another aspect of the problem which has received less attention than it deserves. This is the necessity for females to place their eggs sufficiently close to an adequate supply of food to insure the growth and development of the F, generation. Fulfillment of this requirement is particularly important for those species whose larvae are restricted feeders, that is, monophagous or oligophagous. It is generally assumed that the continued existence of a species is evidence that the eggs are always properly placed. As a consequence of this assumption very few quantitative studies have been undertaken, with the result that the contribution of the adult's behaviour to the degree of survival in larval populations is unknown. The following field studies were undertaken to supply some information on this score.

The present paper is concerned solely with methods of studying the chromosomes, their number, morphology, and behaviour, in insects. Much has already been written on general cytological techniques used in the study of animals and plants (1, 2, 3 and 4) but no special treatment regarding insects has as yet appeared. The techniques outlined in many standard text books are largely obsolete, and reprints of current improvements are frequently not available in the specialised entomological library. Therefore a review of the procedures commonly followed may not be out of place as a guide to the non-specialist.

The evolutionary success of the mites, which rivals that of the insects, is reviewed briefly. A remarkable secondary adaptive radiation apparently occurred in the mites, probably beginning in the late Mesozoic, in conjunction with the major evolution and radiation of the insects and to a lesser extent of the higher plants and the warm-blooded vertebrate animals.

The spectrum of forest floor microhabitats, in which mite–arthropod associations may occur, is discussed. The problems in elucidating the living relationships between mites and other arthropods, due to biological complexities and physical difficulties, are reviewed. Some of the elements of close mite–arthropod associations are discussed, including protected stable habitats provided by insects, shared habitat specificities, regularity of co-occurrence, host specificity, site constancy of mites on their arthropod hosts, and life cycle synchrony.

Examples are given of the apparently few morphological adaptations of insects for accommodating mites. The variety of morphological structures which are adaptations of mites to an association with other arthropods are discussed, particularly regressive modifications. Physiological and behavioral adaptations of mites to secretions or to other actions of their arthropod associates are mentioned. Cases are given showing the different ways in which mites have achieved synchrony of their life cycle with that of their hosts.

Some thoughts on the usefulness of research on the interrelationships between mites and other arthropods conclude the paper.

Microctonus aethiops (Nees) auctt. (Fig. 1) and Perilitus rutilus (Nees) are parasites of adult Sitona weevils in Europe. They were released in Canada as control agents of the sweetclover weevil, Sitona cylindricollis Fahr. (Fig. 2). The immature stages and biology of the species were studied as a prerequisite to attempts at biological control. A similar investigation of the braconid Pygostolus falcatus (Nees) was completed (Loan and Holdaway, 1961). Jackson (1928) described some aspects of the biology of P. rutilus, and additional data are given in the present paper.

Many soil-inhabiting insects are susceptible to entomopathogenic nematodes but the degree of susceptibility ranges widely. Much is understood about the habitat of insect pests in relation to their susceptibility but little attention has been paid to the influence of physical deterrents. "Physical deterrents" is used here to include morphological barriers (passive deterrents) and behavioural responses to attack (active deterrents). The roles of both are reviewed and discussed, in particular with reference to wireworms (Elateridae), a group of insects generally resistant to the nematodes. Knowledge of insect morphology and behaviour as well as habitat is important in predicting susceptibility to entomopathogenic nematodes.

Spatial and temporal variability are essential considerations in the study of aquatic insects. Traditionally, these two sources of variability are treated separately; however, they should be considered together because they occur concurrently in natural systems. To illustrate this interaction, we constructed two-way variability tables in which spatial (habitat, reach or zone, system, intersystem) and temporal (within a day, within a season, within a year, year to year) scales were ordered on separate axes, and examples of concurrent spatial and temporal variability were entered at the intersects of the scales. We examined three aspects of aquatic insect life histories in lotic and lentic waters using such tables: emergence, feeding and growth, and movements and migrations. It proved easier to find examples for the stream tables than for the lake tables, perhaps because of greater spatial and temporal variability in lotic than lentic waters. Also, more papers have been published on stream than on lake insects over the last decade or so. Spatial and temporal scales at which lotic and lentic research is done were determined by examining the recent contents of five key aquatic journals (≈ 500 articles). Research on aquatic insects appears generally to be done at relatively long temporal scales, but at smaller spatial and shorter temporal scales in lotic than lentic systems. Perusal of the literature to find examples of concurrent spatial and temporal variability revealed the prevalence of a “mean-values” appproach to data analysis, in which investigators “homogenize” data to reduce spatial and temporal variability. However, it is this spatial and temporal variability that often provides an explanation of factors causing the patterns observed. A “variance” approach, in which data are disaggregated and fluctuations or extremes are considered, may be far more informative and may elucidate underlying mechanisms.

Differences in resistance of varieties of peas to the pea aphid, Acyrthosiphon pisum (Harr.), have long ago been shown in the field and by controlled rearings under glass, Russell and Morrison (1924, p. 63) apparently being the First to observe differences. Early investigations at Wisconsin by Searb (1932) showed that pea varieties differ in the number of aphids born upon them. Maltais (1937) corraborated these early findings and reported (1950) the development of a pure-line strain of aphid-resistant pea. The influence of resistance in peas upoil aphid development, reproduction, and longevity as investigated by Harrington (1941) with individual plants under controlled conditions in the greenhouse. His results confirmed the inability of the insect to develop and reproduce as fast on a resistant plant as on a susceptible one. Tt has been postulated that the composition of the available food in the host plant plays possibly the most important role in determining the resistance to aphid attack (Evans, 1938; Painter, 1941). Maltais (1948), Auclair and Maltais (1950), and Maltais (1951) gave preliminary reports on the probable factors in varietal resistance in peas.

Seasonal morphometric analysis of 788 adult Polistes metricus Say showed that: (1) Queens sampled throughout the colony cycle were of similar body size but significantly smaller than fall gynes. (2) Queens’ ovaries are large in the spring, decline early in the colony cycle, peak near the mid-postemergence period and decline late in the colony cycle. (3) There are no significant correlations between head width, ovary width, and size of nest in workers or queens. (4) Early and late workers are small but workers emerging during the mid-postemergence period are large. (5) All workers and gynes emerge with small, similar sized ovaries but older workers may develop larger ovaries. (6) Queens are larger than early and late workers but the same size as workers emerging during the mid-postemergence period. (7) The class with the largest adults were intermediates collected when colonies began production of males. These adults, intermediate in fat content between workers and gynes, comprised a large proportion of females emerging late in the colony cycle. (8) The body size of gynes is independent of colony size. (9) Males were significantly more variable in body size than gynes.

Exotic ambrosia beetles (Curculionidae: Scolytinae) in the tribe Xyleborini include destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic: Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky), and Xylosandrus germanus (Blandford). Due to similarities in their host tree interactions, this mini-review focuses on these three species with the goal of describing their host-selection behaviour, characterising associated semiochemicals, and assessing how these interactions relate to their management. All three of these Xylosandrus spp. attack a broad range of trees and shrubs. Physiologically stressed trees are preferentially attacked by X. crassiusculus and X. germanus, but the influence of stress on host selection by X. compactus is less clear. Ethanol is emitted from weakened trees in response to a variety of stressors, and it represents an important attractant for all three species. Other host-derived compounds tested are inconsistent or inactive. Verbenone inhibits attraction to ethanol, but the effect is inconsistent and does not prevent attacks. Integrating repellents and attractants into a push–pull management strategy has been ineffective for reducing attacks but could be optimised further. Overall, maintaining host vigour and minimising stress-induced ethanol are keys for managing these insects, particularly X. crassiusculus and X. germanus.

The comparative ecology of conifer-feeding budworms in the genus Choristoneura Lederer (Lepidoptera: Tortricidae) in Canada is reviewed with emphasis on publications since 1980. Systematics and life history are updated and historical outbreak patterns and their current interpretation summarised. Recent evidence is analysed in the context of ecological interactions among three trophic levels; host plant, budworm herbivore, and natural enemies. The influence of weather and climate are viewed as modulating factors. The population behaviour of budworms is interpreted as the result of tri-trophic interactions that vary at different scales. The result of these multi-scale interactions is that despite shared phylogenetic constraints and common adaptations, different budworm species display different population behaviour because of specific ecological relationships with their respective hosts and natural enemies.

Female southern pine beetles, Dendroctonus frontalis Zimmermann, may propagate two species of symbiotic fungi in a prothoracic mycangium. Females can carry either Ceratocystiopsis ranaculosus Bridges and Perry or an unnamed basidiomycete or both; some carry no fungi. Thus, females can be categorized into one of four groups based on mycangial content. We examined size and lipid content of emerging brood adult females based on these mycangial fungal classes. Female beetles carrying the basidiomycete, either alone or in combination with C. ranaculosus, were larger, heavier, and contained more lipid than did females carrying only C. ranaculosus. Size and lipid content also varied by season, as did the number of females carrying different fungal combinations. Regression analysis showed that variation in the occurrence of the basidiomycete was significantly related to variation in averages of beetle size and lipid content measurements.

Sticky stovepipe traps, flight interception traps, and Lindgren multiple-funnel traps were baited with conifer monoterpenes and ethanol to capture conifer-feeding beetles and their associates. Of the more than 6000 beetles captured, 74.6% were caught by stovepipe traps, 14.8% by interception traps, and 10.7% by multiple-funnel traps. Dominant families were the Scolytidae (14.5% of all beetles captured), Elateridae (14.4%), Lampyridae (12.1%), Cerambycidae (12.0%), Cleridae (10.5%), Curculionidae (9.3%), Staphylinidae (4.0%), and Buprestidae (3.4%), with other families accounting for 19.8% of specimens captured. Conifer-feeding species in the families Buprestidae, Melandryidae, Cerambycidae, Scolytidae, and Curculionidae and their predators (Cleridae) were captured in greatest numbers by the sticky stovepipe traps; the interception traps generally captured the fewest specimens. The sticky stovepipe traps may be superior because they offer a distinct vertical silhouette to approaching insects.

Impacts of Bacillus thuringiensis var. kurstaki (Btk) and defoliation by gypsy moth [Lymantria dispar (L.)] on native, non-target arthropods were evaluated in eastern West Virginia from 1990 to 1992. Adult and larval arthropods were collected by foliage sampling and light-trapping at 24 20-ha (50-acre) plots, representing six replicates of four treatments: unsprayed, gypsy moth absent (control); unsprayed, gypsy moth present (defoliation); sprayed, gypsy moth absent; and sprayed, gypsy moth present. Pre-treatment data were collected in 1990. In May 1991, one application of Btk was made to 12 plots at a dosage of 14.4 BIU/ha (36 BIU/acre). Post-treatment data were collected in 1991 and 1992. With few exceptions, detectable effects from Btk application were restricted to Lepidoptera. Although abundance and species richness of larval and adult non-target Lepidoptera decreased at all plots between 1990 and 1992, abundance and species richness were reduced at Btk-treated plots relative to untreated plots. Richness and abundance of some larval and adult Lepidoptera declined at defoliation plots. Although the short-term (< 1 year) impacts of Btk application on non-target Lepidoptera are negative, the long-term effects (> 1 year) of reduced abundance of gypsy moth larvae may be beneficial for some native species. Although Btk application and defoliation reduce abundance of native Lepidoptera, environmental conditions such as weather may have a greater influence on population fluctuations.

The European spruce sawfly, Diprion hercyniae (Htg.), was first discovered in Canada in 1930 and in the next few years attained outbreak proportions in spruce forests over large areas in the Gaspé Peninsula and New Brunswick. The accidental introduction of a polyhedrosis in the early 1930’s was responsible for the rapid decline of the infestation, and under the influence of both disease and introduced parasites, densities throughout the range of the sawfly have been fluctuating at very low levels for the past 20 years. Population studies have been conducted on this insect in New Brunswick since 1938 and data are now available for 50 consecutive generations over a 25-year period. Morris’ key-factor approach, using parasites, disease and weather as the key factors, has been used in the analyses of the data. Although disease obscured the effect of other control factors, during high sawfly densities, larval parasites have been largely responsible for maintaining the low densities experienced in New Brunswick for the past 20 years. A pronounced change in the relative importance of the different parasite species and in the amount of cocoon predation attributable to small mammals and wireworms has occurred during the change from high to low host densities.

A faunal list of 362 sub-fossil Coleoptera obtained from 33 published and 24 unpublished sites of Pleistocene age in Canada and the neighbouring United States is given. A table indicates the distribution of families, with the number of species encountered, through discrete intervals of Pleistocene time. Seven species representing members of the Carabidae, Hydrophilidae, Staphylinidae, and Scolytidae have been used to illustrate distribution changes through the last interglacial/glacial/present interglacial cycle. The maximum distance so far recorded is a shift of over 9000 km for Anotylus gibbulus (Epp.), a staphylinid, found fossil in Toronto during the last interglacial, and today recorded only from Eurasia and Asia. A number of other species whose modern ranges are confined to northwestern North America have been found fossil in the Great Lakes – St. Lawrence region, over 4000 km distant. A similar shift is noted in species which today are found only in the eastern Canadian Arctic. Aspects of ice build up, marginal conditions outside the Laurentide Ice Sheet limits, Pleistocene climates, paleoecology, and sub-fossil insect localities are used to formulate hypotheses about three refugia around the perimeter of the Late Wisconsinan ice.

The effect of conservation and conventional tillage on carabid communities was compared using pitfall trapping in two commercial barley (Hordeum vulgare L.) fields located 4 km apart on similar soils. Carabid abundance was significantly higher under conventional tillage but abundances of individual species varied between the two fields. Agonum placidum Say and two Amara Bonelli species were more abundant at the conventional tillage farm whereas Pterostichus adstrictus Eschscholtz and three Bembidion Latreille species were significantly more abundant at the reduced tillage farm. Slightly more carabid species were collected in this latter field and species diversity and evenness were significantly higher.

In Rhodnius, a volatile substance produced by mating pairs is attractive to male insects. The pheromone acts also as a sexual stimulant; males respond in the absence of females by attempting copulation with other males. Air swept over mating pairs and conducted to a cage at a considerable distance proved to be highly attractive to males. Proximity of the sexes, without opportunity for actual contact, does not stimulate production of the pheromone. Since males and females will copulate only after a blood meal, feeding is a prerequisite to pheromone production. Also, unfed males will not respond to the attractant. Males of this nocturnal species were stimulated only in complete darkness.