This is an analysis of the attempts to colonize at least 208 species of parasites and predators on about 75 species of pest insects in the field in Canada. There was colonization by about 10% of the species that were introduced in totals of under 5,000 individuals, 40% of those introduced in totals of between 5,000 and 31,200, and 78% of those introduced in totals of over 31,200. Indications exist that initial colonizations may be favoured by large releases and by selection of release sites that are semi-isolated and not ecologically complex but that colonizations are hindered when the target species differs taxonomically from the species from which introduced agents originated and when the release site lacks factors needed for introduced agents to survive or when it is subject to potentially-avoidable physical disruptions. There was no evidence that the probability of colonization was increased when the numbers of individuals released were increased by laboratory propagation. About 10% of the attempts were successful from the economic viewpoint. Successes may be overestimated if the influence of causes of coincidental, actual, or supposed changes in pest abundance are overlooked. Most of the successes were by two or more kinds of agents of which at least one attacked species additional to the target pests. Unplanned consequences of colonization have not been sufficiently harmful to warrant precautions to the extent advocated by Turnbull and Chant but are sufficiently potentially dangerous to warrant the restriction of all colonization attempts to biological control experts. It is concluded that most failures were caused by inadequate procedures, rather than by any weaknesses inherent in the method, that those inadequacies can be avoided in the future, and therefore that biological control of pest insects has much unrealized potential for use in Canada.

The development of physiological resistance in insect populations of agricultural and public health importance to insecticides and other methods of control has taken on proportions of increasing importance. In this paper, a mathematical pest population model is presented which can be used for dynamic economic and ecological evaluation of alternative control strategies. Because of the unique nature of pest populations, the model is not directly applicable to all actual problems. However, the model is an illustration of a whole class of models that promises to remove pest control strategies from the category of ad hoc decisions.

For those empirical problems for which a benefit function can be defined, dynamic programming is suggested as a method for determining an optimal strategy over time. When it is difficult or impossible to specify a benefit function, which is frequently the case, it is suggested that Monte Carlo techniques, applied to the pest control strategies of interest, be used to determine the effects on the pest population over time.

A mathematical model relating mosquito densities and meteorological variables is given. The model is developed from observations on a real mosquito population and forecasts future mosquito densities from information about mosquito densities, amount of rainfall, and temperature at past points in time.

Observations were made on the flight patterns, sex ratios, and ovipositional activity of Pissodes strobi in Sitka spruce. There is an aggregation of adults on spruce leaders early in the flight season during which sexual maturation and mating take place. Males are more active early in the flight season, while females are more numerous during the latter half of the flight season.

A revision is presented of the species of Graphomya Robineau-Desvoidy found in North America. Nine species are recognized of which two, G. americana R.-D. and G. idessa Walker, are resurrected from synonymy under G. maculata (Scopoli), and the others, G. occidentalis, G. interior, G. columbiana, G. minuta, G. ungava, G. alaskensis, and G. transitionis, are described as new.

A review of the taxonomic position and biological information of the genus Graphomya is presented. Keys are provided for both males and females of the species from North America. Each species is described and biological information, when known, is presented. Distribution for each species is presented by locality records and a distribution map. A generic diagnosis for Graphomya from North America is also given.

Factors affecting the extraction and bioassay of the sex pheromone of white-marked tussock moths were evaluated. Dipping the female pheromone glands in a solvent (preferably hexane) to produce a wash containing active material was a particularly effective and reproducible method of obtaining a potent extract. These were most active if obtained from virgin females < 2 days old. Extracts from recently mated females were only slightly less active than those from virgin females. Males were most responsive in bioassays when 2 to 3 days old. The maximum percentage response of males was obtained at 1 × 10−4 FE (female equivalents); beyond this concentration the percentage response decreased. Characteristically, extracts lost their potency within 1–3 weeks of preparation. It is suggested that either an inhibitor or loss of a chemical component of the sex pheromone causes an extract to become inactive.

Eight new high altitude species of the subgenera Microsaurus (Steph.) Smet., Quedionuchus Shp., and Raphirus (Steph.) Smet. of the genus Quedius Steph. (Staphylinidae) from Mexico are described as new.

Quedius (Raphirus) advena Shp. is redescribed, and a lectotype is designated.Each species is described and illustrated. A key to all nearctic species of the caseyi-group of the subgenus Microsaurus, and of the aenescens-group of the subgenus Raphirus is given.

Two Old World limnephilid genera are recorded from North America for the first time: Chilostigma with C. itascae n. sp; and Ecclisocosmoecus to which is transferred the former Ecclisomyia scylla Milne. Three new species are also described in other genera: Dicosmoecus schmidi n. sp., Cryptochia denningi n. sp., and Neothremma andersoni n. sp. The taxonomic status of the genus Psychoronia is reviewed.