Conceptual and nomenclatural problems of Digamasellus Berlese, 1905 and Dendrolaelaps Halbert, 1915 are reviewed. It is shown that Digamasellus punctum (Berlese, 1904) is conspecific with D. perpusillus Berlese, 1905, the type-species of Digamasellus Berlese, 1905 (new synonymy). Hence, the genus in which punctum is included must take the name Digamasellus.A new case is made for recognizing Digamasellus and Dendrolaelaps as distinct genera in the Digamasellidae. Two other genera of Digamasellidae are recognized, Dendroseius Karg, 1965 and a broadened concept of Longoseius Chant, 1961. Two new subgenera are proposed, Dendrolaelaspis in the genus Dendrolaelaps, and Longoseiulus in the genus Longoseius. Diagnoses, descriptions, and a key to these genera and subgenera of Digamasellidae, along with a comprehensive description of the family, are presented. The phylogenetic relationship of the Digamasellidae in the Rhodacaroidea, and some thoughts on phylogeny within the Digamasellidae are given.A second species of Digamasellus sensu stricto, D. australis, is described as new, and the female and male adults of the type-species of Longoseius, L. (L.) cuniculus Chant, are described for the first time. New combinations include: Dendrolaelaps (Dendrolaelaspis) orientalis (Bhattacharyya), Longoseius (Longoseiulus) longulus (Hirschmann), L. (L.) ornatus (Hirschmann), L. (L.) aberrans (Hirschmann), and L. (L.) brachypoda (Hurlbutt).The absence of the protonymphal seta, md, from the telotarsi of legs II to IV is noted as a singular deficiency in the leg setation of Longoseius cuniculus Chant. This seta is not known to be absent in any other species among the families of Gamasina.A paper published by Hirschmann while the present work was in press is considered in an addendum to this paper. The subgeneric name Dendrolaelaps (Tridendrolaelaps) Hirschmann, 1974 is an objective junior synonym of Digamasellus Berlese, 1905, and the latter also has priority over Dendrolaelaps Halbert, 1915 so long as both names are applied within the same genus. A lectotype is designated for the nominal species Digamasellus punctum (Berlese). The status of the subgenus Dendrolaelaps (Multidendrolaelaps) Hirschmann, 1974 is problematic, pending a more comprehensive diagnosis providing data sufficient to indicate whether this is a monophyletic group. The quadrisetus group is newly proposed for some of the species placed by Hirschmann in the armatus group of Multidendrolaelaps. Digamasellus badenhorsti (Ryke) is tentatively considered as the second known species of Dendroseius Karg. Hirschmann's opinion, that Longoseius Chant warrants no more than a species-group in Dendrolaelaps, is disputed.

This paper presents a sampling plan for estimating numbers of H. postica larvae in the spring growth of alfalfa. A 6-stem bouquet of foliage formed an appropriate sample unit. The pattern of counts for all four instars conformed to the negative binomial distribution, and variance analysis for 89 sets of data revealed that differences between block, plots, and quadrats generally were not significant. For moderate levels of infestation (ca. 12 larvae per bouquet), estimates with acceptable precision may be obtained by taking a single 6-stem bouquet from each of 16 randomly selected ft2 (0.9m2) quadrats within a field, at a total cost of 120 man-minutes.

The cinnabar moth, Tyria jacobaeae L., was established in the Atlantic provinces and British Columbia for the control of tansy ragwort. Establishment was difficult to obtain with imported stock: only two of 14 colonies survived, one on each coast. The rate of survival in these colonies increased with succeeding generations, and with stock from the regional colony eight of nine releases became established in Nova Scotia. Most of the established colonies increased until the ragwort was defoliated.

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 eggs of 18 species of cutworms of the subgenus Euxoa Hübner are described and a key for separating some of them has been constructed. Only in rare instances can species be identified from egg morphology alone, but the egg stage can usually be identified to the subgeneric level.

Large numbers of black flies, mostly Simulium venustum Say, were labelled as larvae with 32P and released in rapids in the Chalk River near the village of Chalk River, Ont., to complete development and disperse as adults. Flies were trapped over a 900 square mile area for 3 months after the release, and radioactive flies from the traps were identified at CRNL by means of an autoradiographic technique. The distance travelled by the flies could be described by a normal distribution curve, with the average migration between 5.8 to 8.2 miles. A few individuals were trapped at a distance of 22 miles 2 days after emergence, and some crossed the Ottawa River which is at least a mile wide at the point nearest the release area. Some traps caught very high numbers of radioactive flies, one at about 6 miles from the release center accounting for more than 1300 tagged flies. The traps giving the highest number of tagged flies (e.g., > 100) were clustered in two distinctive areas, one west and one large area south of the release point. The results indicate that control measures should be applied to black fly streams at least 10 miles from critical areas such as towns.

Lecanium tiliae (L.) is now attacked in British Columbia by three species of parasites, about 18 predators, and a fungus. Parasites are the most important natural enemies but parasitize an average of only 30% of the scales. Reasons for low parasite effectiveness include: hyper-parasitism by one species, Coccophagus lycimnia, which is apparently a recent arrival in the district, on itself and on the chief parasite, Blastothrix longipennis; a tendency for C. lycimnia to be relatively abundant in low scale populations; differences in sex ratio of B. longipennis between low and high host populations; and parasite mortality in the scales. It was confirmed that the parasites pass the summer as diapausing adults rather than in alternate hosts. It is concluded that the biological control attempt of 1928 and 1929 that has been widely regarded as a success was in fact probably a failure, as the introduced parasite, B. sericea, did not apparently become established. An attempt in 1969 and 1970 with an introduced fungus also failed.

The effect of host age of the cabbage looper, Trichoplusia ni (Hübner), on ovipositional rate and successful parasitism by Hyposoter exiguae (Viereck), a solitary endoparasitoid was investigated. Success in parasitism of T. ni was correlated with host age. Successful parasitism of hosts exposed as first, second, or early third instar larvae, ranged from 83 to 88%. A decline in parasitism was observed for the remaining instars with a low of 27% for mid-fifth instar larvae.

A different relationship between host age and successful parasitism was observed in tests where all five instars of the host were presented to the parasitoid simultaneously. Successful parasitism was highest among second and third instars, approximately 75% for both, and lowest for fifth and first instars, 10% and 30%, respectively. A significantly higher rate of mortality was found for first instar hosts.

The ovipositional rate of H. exiguae was related to host age. The parasitoid deposited an average of 2.3 and 1.3 eggs per 24 h in first and second instar T. ni, respectively The number of eggs/host and degree of superparasitism declined in older individuals and differed statistically for each instar. The percentage parasitism differed statistically for all but first and second instar larvae.

The subtribe Aphrodina of the Aphrodini is an essentially Palaearctic group with eight Nearctic species, of which six are apparently all recently introduced from Europe to North America. The subtribe comprises four genera: Aphrodes Curtis with six species, Planaphrodes n. gen. with 15 species, Stroggylocephalus Flor with four species, and Anoscopus Kirschbaum with nine species.

The genera and species of the Nearctic Region are keyed, and notes are provided on North American literature pertaining to distribution, nomenclature, and the earliest records of the introduced species. The northern hemisphere species are illustrated, and their apparent relationships are discussed.

By type examination, the synonymy of Cicada rustica Fabricius 1775 with Aphrophora salicis (DeGeer) 1773 is confirmed and the following new synonymies are established: Acucephalus circumflexus Provancher 1889 = Anoscopus albiger (Germar) 1821; Acocephalus bifasciatus nigricans Matsumura 1912 = Planaphrodes sahlbergi (Signoret) 1879; and Acucephalus bifasciatus guttatus Matsumura 1912 = Planaphrodes japonica (Dlabola) 1960, as Planaphrodes guttata (Mm.). An index of all usages of trivial names in the Aphrodina is given.

Since 1970 the increasing level of Colorado potato beetle infestation in southwestern Ontario has necessitated foliage sprays or planting treatments with systemic insecticides. Spray tower tests of many insecticides against eggs, larvae, and adults indicated that the best overall materials would be carbofuran, azinphos-methyl, and chlorfenvinphos.

At planting time furrow treatments with granular carbofuran, disulfoton, or phorate demonstrated good control of all potato pests until the end of June. After that time only the carbofuran and phorate treatments gave protection against a heavy second generation of potato beetles. Yields were related to the degree of pest control.

Several species of wireworms were attracted to germinating wheat, air from flasks of germinating wheat, decomposing oatmeal, commercial CO2 and, in addition, germinating seeds of eight other cultivated plant species. Larvae located a biological or experimental source of CO2 by a directed movement along CO2 gradients, from distances up to 20 cm.

Methods and apparatus for measuring small CO2 gradients, using gas chromatography and mass spectrometry, are described. Ctenicera destructor (Brown) larvae apparently responded to CO2 gradients between glass plates, that ascended on the average by 0.002% (soil) and 0.005% (agar)/cm over a distance of from 12 to 16 cm. The "sensitivity threshold" was calculated as being 1–2 ppm over the distance involved in one deflection of the head during klinotactic orientation. Attractancy was observed within a range of CO2 concentration from about 0.036% to 1.5%. Repellent effects did not appear to be only related to concentration, but possibly were due to steepness of the gradient and(or) previous exposure to CO2.

Passing an air stream from germinating grain over a KOH solution eliminated the attractancy of the grain by removing the CO2 and possibly other undetected attractants. A small percentage of C. destructor larvae apparently oriented to an ethylene source, but it was concluded the CO2 was the most important if not the only attractant from germinating wheat seeds.

An autocidal control method involving attraction of ovipositing females to artificial oviposition sites, rearing and chemical sterilization of adults reared from the collected eggs, and release of sterilized males back into the system was field tested with the mosquito Culex restuans Theobald. This species cannot be cultured continuously. The average weekly percentage of sterile egg rafts was 2.4 (range 0.3–16.0) in the test area where sterile males were released (av. 9620/wk) and 5.3 (range 1.5–30.0) in the area where both sterile males (av. 7000/wk) and untreated females (av. 4590/wk) were released. The low level of sterility achieved is attributed to infiltration of gravid females from outside the experimental areas, poor efficiency in producing sterile males from the collected egg rafts, and the small scale of the test.

A hypothetical model is used to compare theoretical reduction in rates of increase of a population of mosquitoes when various proportions are induced to oviposit in ‘trap’ pools if the eggs trapped are destroyed, reared to produce sterile males for release, or reared to produce sterile males for release in conjunction with larvicidal treatment of uncontrolled breeding areas.

Laboratory studies were conducted to determine the toxicity of a number of insecticides to adults of the carrot weevil, Listronotus oregonensis (LeConte). Initial screening tests indicated that, in general, carrot weevil adults were quite tolerant to insecticides. However, several materials showed sufficient activity as direct contact, residual contact-stomach, and soil insecticides to warrant testing under field conditions. These included Zinophos® (O,O-diethyl 0–2 pyrazinyl phosphorothioate), WL 24073 [O-(2-chloro-l-(2,5-dichlorophenyl)vinyl) O-methyl ethylphosphonothioate], WL 25735 [O-(2-chloro-1-(2,5-dichlorophenyl) vinyl) O-methyl methylphosphonothioate], Pirimiphos-methyl® (O-[2-(diethylamino)-6-methyl-4-pyrimidinyl] O,O-dimethyl phosphorothioate), tetrachlorvinphos, and parathion. Although less active, Biothion® [(O,O′-thiodi-p-phenylene) O,O,O′,O′-tetramethyl phosphorothioate], carbofuran, and chlorpyrifos were also considered sufficiently effective to warrant further study.

The salivary glands of female Culex pipiens L each consist of three lobes divisible into five regions. Fine structure indicates that two regions may be involved in solute-linked water transport and three regions may have a glandular function. The fine structure is similar to that reported for Anopheles stephensi and Aedes aegypti. In C. pipiens, an axon of presumed neurosecretory function was found associated with the neck region of the medial lobe.

Complete development of the salivary glands occurs between the first and fifth days of adulthood. Morphological changes associated with blood-feeding were limited to the presence or absence of the salivary secretions in the apical cavities and duct lumen. During blood-feeding the contents of two of the glandular regions are voided, being replenished within 24 h Results are related to previous histochemical studies of the salivary glands of mosquitoes.

The cabbage maggot, Hylemya brassicae (Bouché), had three generations per year from 1970 to 1973 inclusive, a partial fourth was noted in most years. A small proportion of first generation pupae entered aestivation in 1971.

Thermal units required for fly emergence from overwintered pupae fell within a narrow range (174 to 199), but there was little correlation between thermal units and fly emergence in subsequent generations. Lack of adequate moisture delayed establishment of larvae in roots in some generations. Lack of adequate soil moisture delayed establishment of larvae in roots in some generations, and this appeared to be the chief reason for the lack of correlation between thermal units and fly peaks.

Throughout this investigation the over-all population remained remarkably constant. Parasitism by a staphylinid, Aleochara bilineata Gyll., and a fungus, Strongwellsea castrans Batko and Weiser, and soil moisture were the most important biological and climatic factors affecting survival. Parasitism of the adult by a nematode, Heterotylenchus sp., was recorded for the first time.

Although large numbers of seed maggot adults, Hylemya florilega (Zett.) and H. platura (Meig.), were recorded, few infested rutabaga. Other species trapped included Euxesta notata (Weid.) and Muscina spp.

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.

The biology of Coenagrion angulatum Walker and C. resolutum Hagen in Saskatchewan has been studied. In these species embryonic development begins as soon as the eggs are laid and is completed in the field within 3 weeks. Larval development is rapid and larvae in the final instar were first collected before the middle of September. Development ceases during the first 2 weeks of October when the water temperature is about 2 °C. By this time the majority of larvae are in the last three instars. Larvae overwinter frozen in the ice 15 to 20 cm below the pond surface. They are able to survive temperatures as low as −5° to −6 °C though these extremes are not normally experienced in the field because of snow cover. Although the study pond filled with runoff water by mid-April no change in the larval population structure occurred until mid-May. Emergence, which is highly synchronous, begins in the last week of May. However, it is governed by the prevailing air and water temperatures, and occurs only when the mean daily water temperature exceeds 12 °C and the mean maximum air temperature reaches 20° to 21 °C. Most insects emerge within 10 days of the first appearance of the adults. Sexual maturation takes about 1 week. Oviposition occurs while the pair are in tandem. Preferred oviposition sites are the submerged portions of stalks of floating plants such as Utricularia, Ranunculus, and Potamogeton. The observations are discussed in terms of the species’ ability to survive the climatic extremes of central Canada.

In the early 19th century, malaria was indigenous in Upper Canada (Ontario), but indigenous infection has not been seen in Canada since about 1909. For many years mosquitoes were regarded principally as harmless pests of man and domestic animals until the recognition of a number of mosquito-borne viruses. At present, mosquitoes in Canada are known to be involved in the maintenance or spread of at least seven arboviruses. One of these viruses, western equine encephalomyelitis, occurs in epidemics in man and horses at irregular intervals in the western provinces. The extent to which the other arboviruses might cause disease in man or domestic animals in Canada is unknown at present but California encephalitis virus infection rates can be high in human residents of central Saskatchewan, central Alberta, and southern British Columbia. On the basis of observations made in the United States, St. Louis encephalitis virus could pose a threat to public health in Canada whereas the Cache Valley virus might involve livestock. Even if man and livestock are not involved at present in epidemics of disease due to these viruses, the presence of the viruses and their vectors should be of concern. Epidemics could arise either from amplification of causal viruses already present in indigenous foci or by amplification of viruses from new enzootic foci recently established by extension of the geographic ranges of the viruses. Evidence indicating which category each of the known viruses in Saskatchewan belongs to is briefly reviewed. Japanese B encephalitis virus has not yet been seen in Canada but the environmental prerequisites for an epidemic or epizootic due to this virus appear to be present and awaiting the arrival of the virus.

An instance of medium-range migration by Rhopalosiphum maidis (Fitch) and of long-range migration by Spodoptera frugiperda (J. E. Smith) are documented and the weather systems that made the migrations possible are detailed. Although both species were carried beyond their northern limit for overwinter survival and little damage ensued, the usefulness of synoptic weather analysis in explaining sudden population increases is shown.

Two mature male adults of Anax Junius were seen in Ontario exceptionally early in spring, before emergence had begun locally, and very soon after an episode of unseasonably warm weather which was associated with the arrival from Texas of a low-pressure system.