The life history of the Sitka spruce weevil, Pissodes sitchensis Hopk., is described. Adults overwinter in duff at the base of trees and emerge in April or early May. Oviposition begins in late April on leaders. The larvae hatch and mine downward, eventually girdling and killing the leader. Larvae pupate in chip cocoons under the bark. Newly developed adults start emerging in August and, prior to hibernation, feed on leaders of young trees. Adults have been observed in the field as late as December.

Predators caused heavy mortality but the weevil population maintained itself and increased in some years. Parasitism was light. Natural control factors reduced the population level but were incapable of controlling a population. Satisfactory control was obtained by applying DDT and phosphamidon to leaders with a hand-sprayer early in the spring, but repeated applications would be necessary to protect a plantation through the critical years.

Damage to Sitka spruce regeneration and plantations in British Columbia is severe. At present, protection of Sitka spruce plantations would require considerable expense.

Larvae of Pseudaletia unipuncta (Haw.), reared on corn foliage, were found to vary in the rate they were able to feed, grow, and attain maturity. Mortality varied inversely with the rate of food intake. In the fifth and sixth instars, there was a direct linear relationship between rate of food intake and daily growth, and rate of food intake and daily development. A variance of 78 to 96% in final weights of the two stages was explained by the combined effect of initial weights of larvae, food supply, duration of feeding, and food ingested. Fecundity increased with the rate of food intake of the larvae.When P. unipuncta feeds at a high rate, it is able to accelerate development, increase growth, and maintain a high reproductive potential. When the rate of food intake is low, development, growth, and fecundity are reduced for the sake of survival.

Four species of Cruciferae [canola species Brassica rapa L. and Brassica napus L., and mustard species Brassica juncea (L.) and Sinapis alba L.], and various cultivars of each species, were evaluated for susceptibilities to infestation by Delia spp. (Diptera: Anthomyiidae) under field conditions in central Alberta, Canada. Susceptibility was measured throughout the season by recording numbers of eggs of Delia spp. laid on or near individual plants, and at the end of the season by a semi-quantitative determination of injury inflicted by larvae on taproots. Differences in susceptibility occurred among and within canola and mustard species. Plants of B. rapa were most susceptible to Delia spp.; both mean eggs per plant and mean damage ratings per plant on B. rapa significantly exceeded those of all other species studied. Intermediate susceptibility was observed for plants of B. napus and B. juncea; plants of S. alba were least susceptible. In general, differences in susceptibility were greater among species than among cultivars within species. Root damage generally correlated with oviposition among and within species, suggesting that the mechanism of resistance by cruciferous species to infestation by Delia spp. is antixenosis or nonpreference. Results of this study indicate that canola growers in regions infested annually by high population densities of Delia spp. should seed B. napus or B. juncea rather than B. rapa. However, if a short growing season necessitates seeding B. rapa, then growers should select the more resistant cultivars of this species.

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.

Adults of most species of insect parasites spend much time finding objects that influence their individual and collective well-being. The object found at any time is usually correlated with the physiological state of the parasite and with extrinsic factors existing at that time. From the standpoint of the species' economy, the most important objects to be discovered are hosts on which fertile parasite progeny can mature. Whether hosts are found and parasitized is influenced, to varying degrees with different parasite species, by whether the female has already found, or been found by, a male of the same species, and by whether she has already located food other than that provided by hosts. The present study is of factors that affect host finding by females of a pteromalid, Nasonia vitripennis (Walk.).

Many factors influence the host preferences of entomophagous insects and have an important role in determining the fate of parasites in the field. Some of the factors influence the ability of parasites to locate their hosts. Others determine the suitability of the host as a medium for larval development (7, 15, 18, 26, 27, 31). These factors together determine the range of hosts attacked and control the degree to which nonpreferred hosts are selected.

Dusky wireworms, Agriotes obscurus (L.), aggregated at rows of wheat, Triticum aestivum L., spaced 1 m apart within 6 d of seeding. Wireworms also aggregated at rows of newly planted strawberries, Fragaria × ananassa Duchesne, resulting in 43% plant mortality. Wheat rows planted 8 d in advance of intercropped rows of strawberries aggregated wireworms at the wheat rows rather than at the strawberry rows. Mortality of strawberry plants protected by the previously planted wheat rows was only 5.3%. Strawberry seedlings planted 14 d before intercropping with wheat rows incurred 29.6% mortality. These data show that trap crops of wheat planted 1 week in advance of planting strawberries can effectively reduce wireworm feeding and plant mortality and can be used as an inexpensive pest management method.

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.

After about 20 years of wide usage in integrated pest management (IPM) programs on peach in the Niagara Peninsula of Ontario, populations of Oriental fruit moth, Grapholita molesta (Busck), resistant to azinphosmethyl and phosmet have been selected. Resistance, as expressed in first-instar larvae, was only two- to four-fold to azinphosmethyl or phosmet, but up to 45% fruit infestations have been documented in commercial blocks. Resistance to azinphosmethyl was not well expressed in adult Oriental fruit moths. In tests with larvae, cross-resistance occurred to most other organophosphorus insecticides except acephate and chlorpyrifos. Acephate was more toxic to resistant than to susceptible larvae. Resistance was higher (> 100-fold) to the methyl carbamates carbaryl and carbofuran but was approximately fivefold to the carbamoyl oxime methomyl. Cross-resistance to pyrethroids was not observed. Tests with field-collected material, either from crosses on mating trays in the field or from pupae collected in cardboard bands attached to trees, indicated that resistance was widespread across the Niagara production area but that the resistance was not uniformly expressed at all locations. Resistance was expressed in F1 larvae from crosses of susceptible females with field-collected males, indicating that the genetic change in resistant larvae was unlikely the effect of a single recessive gene. Field tests in replicated two-tree plots and in larger (0.25–0.6 ha) plots treated with up to five applications as a season-long control program indicated that neither chlorpyrifos nor acephate were as effective as a pyrethroid (deltamethrin). The sustainability of these IPM programs and potential resistance management strategies are discussed.

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.

Phytoplasmas are bacterial plant pathogens consisting of more than 50 phylogenetic groups that cause devastating diseases in various crops worldwide. They are obligate parasites restricted to the phloem tissue of the host plant and are transmitted from plant to plant mostly by leafhoppers (Hemiptera: Cicadellidae). They reproduce within the tissues of their insect vectors and are transferred in the salivary secretions to new host plants during feeding. Phytoplasma epidemiology involves a tritrophic relationship between the pathogen and usually several hosts and vectors. The host-plant range depends on the number of vectors, their feeding habits, and their dispersal pattern. Interactions between phytoplasmas and their vector hosts are complex and influenced by insects' vectoring abilities and the consequences of infection for vectors. In Canada, seven phytoplasma taxa have been detected in various crops. Aster yellows, the primary vector of which is the leafhopper Macrosteles quadrilineatus (Forbes), is the most common and widespread. X-disease, transmitted by at least eight leafhopper species, is economically damaging to all cultivated species of Prunus L. (Rosaceae). Clover proliferation, also transmitted by M. quadrilineatus, is the causal agent of important diseases such as clover proliferation and alfalfa witches' broom. Ash yellows and pear decline have caused economic problems for several decades, while bois noir, a quarantinable disease in Canada, was detected in Ontario and British Columbia for the first time only recently. Because of their cryptic nature, phytoplasmas are difficult to manage; quarantine measures and insecticide sprays remain the most common control measures. However, integrated pest management techniques using beneficial insects, biotechnology, and plant resistance are emerging.

Bumble bees rely on stored nectar to maintain high colony temperatures. This study examines some of the costs associated with exhausting stored nectar for a day in confined colonies of Bombus occidentalis Greene and B. melanopygus Nylander. Workers from energy-deprived colonies ceased incubating and allowed brood temperatures to drop to ambient levels. Workers from energy-rich colonies responded to a simulated vertebrate predator by actively moving about and buzzing loudly (apparently searching for the source of disturbance), but those from energy-depleted colonies mostly remained stationary on the comb. Workers from energy-rich colonies responded to an intruding social parasite (a Psithyrus insularis Smith queen) by chasing and attacking it, whereas those from energy-depleted colonies adopted stationary threat postures. In both cases, the more successful defensive strategy of simultaneous attack by several workers was not employed by nectar-depleted colonies. Cooling of final-instar larvae and pupae added to their development times (disproportionately so in the case of pupae), but low temperature per se did not affect their probability of survival. Hence, the costs of short-term energy shortfall include increased susceptibility to predators and parasites and a lengthened period of development. These costs probably relate to energy stores in a nonlinear manner, providing the foundation upon which risk-sensitive foraging decisions can be based.

Drawing retrospectively and collectively on results of a single individual and his associates covering some 22 years of field and laboratory studies, the authors present three documented case histories of technically complete biological control. They use these examples to illustrate the potential for greater use of this method of pest control, and they discuss the theory of biological control as related to whether or not introductions of a complex of enemy species will inherently lead to competitive interference and a lesser degree of control than if only the "best" species were introduced. They conclude that the three case histories are a refutation of this thesis, as are certain theoretical considerations, and the net results from all biological control programs on a worldwide basis.The authors also point to weaknesses in the use of currently available methods for quantitatively rating or appraising the control and regulating power of density-dependent factors that act with a lag (entomophagous parasites and predators), and emphasize chat regression and modelling methods should be used in conjunction with "check-methods" or other experimental means.

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.

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.

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 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.

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.

Traps baited with either ethyl (E,Z)-2,4-decadienoate (pear ester) or (E,E)- 8,10- dodecadien-1-ol (codlemone) (Pherocon® CM-DA™ and Megalure CM™ lures, respectively) were used to develop action thresholds for codling moth (Cydia pomonella (L.)) in apple (Malus domestica Borkh.; Rosaceae) orchards treated with sex pheromones for control of this pest. Studies were conducted in 102 orchards treated with 500–1000 ISOMATE®-C PLUS dispensers per hectare during 2000–2002. Pairs of traps were placed within two 1.0-ha plots within each orchard. Fruit injury was assessed at mid-season and prior to harvest in each plot. The numbers of female and total moths caught in pear ester-baited traps and male moths caught in codlemone-baited traps were used to develop action thresholds. Thresholds were based on the minimum cumulative number of moths per trap in ≥95% of traps in unsprayed plots with no fruit injury. Specific thresholds were established for the first insecticide spray targeting the start of egg hatch and for the first and second moth flights. The proportion of plots with mid-season fruit injury that had cumulative moth catches below the action threshold at first spray and at second moth flight was determined using the established action threshold and thresholds reduced incrementally to ≥1 moth per trap. Moth catches below the threshold at first spray were less common in plots with high levels of fruit injury (>0.3%) than in plots with low levels of fruit injury and more common with codlemone-baited traps than with pear ester-baited traps. An action threshold of ≥1 moth in a pear ester-baited trap at first spray eliminated the error in predicting fruit injury in plots at mid-season. Conversely, a high proportion of traps baited with either lure failed to predict low levels of fruit injury at harvest in unsprayed plots regardless of the cumulative moth threshold used during the second moth flight.