The occurrence and abundance of larvae of Chironomus tentans Fabricius in saline lakes in central British Columbia were studied with respect to: (1) physico-chemical properties of the lakes, (2) physical composition of the bottom muds, (3) food availability, and (4) co-occurrence with other species of chironomids. The study was done to determine the ranges of environmental conditions to which the larvae are adapted and to identify specific environmental factors which might be of particular significance to natural selection. Abundance was significantly correlated with the amount of food available; the numbers of individuals of other Chironomus present; the percentage of mud particles in the 0.59–0.83 mm range; pH; conductivity; and the concentrations of potassium, magnesium, chloride, sulfate, and dissolved oxygen. In general, occurrence was affected by the same factors which affect abundance. Additionally, larvae did not occur when hydrogen sulfide was greater than 0.3 p.p.m. The ecological data are particularly relevant since they provide a basis for studying the evolutionary significance of ecological adaptation in C. tentans.

Investigations begun in 1947 in Saskatchewan have provided new data on the life-history and habits of the black fly Simulium arcticum Mall. The only published account of the biology and egg-laying habits of this species is that by Cameron (1922). He states that the eggs are laid in the usual black-fly fashion, i.e., attached in masses to rocks wetted by sprav in river rapids. The evidence here reported, however, indicates that the eggs are laid singly over the surface of flowing water and that these eggs settle and beconie embedded in the sand on the bottom. The investigations have conclusively shown that the species over-winters in the egg stage. These facts, important in an understanding of the biology of the species, are of particular value in planning a sound program of control.

Several authors have observed that Rhagoletis pomonella (Walsh) is usually less prevalent during hot dry summers than during cool wet summers (Rivard 1968). Neilson (1964) showed that the emergence of R. pomonella, under laboratory conditions, was affected by the relative humidity of the air. When the relative humidity was 20 or 40%, high mortality occurred during metamorphosis and fewer adults emerged.

The object of this study was to measure the influence of soil moisture on success and time of emergence in a laboratory experiment. The information is needed to improve the forecasting system for apple maggot control in apple orchards (Trottier, in press).

Eighteen new host records were established among 12 species of parasites and 4 species of Ips beetles. Large numbers of Ips spp. and their associates were secured by mass rearing in specially constructed rearing drums. Confirmation of parasitism was accomplished by individual rearing of parasites in gelatin capsules from Ips larvae and pupae taken from logs. Some parasites were typically associated with a particular tree host, but it was not determined if it was due to tree host, Ips host, or the physiographic province. Parasitism was highest in the upper bole, especially in loblolly pine, but no correlation with bark thickness was established. The density of Ips attack and the time during which Ips infestations were maintained at one location also did not appear to affect the rate of parasitism. Parasitism was highest in the overwintering broods of Ips.

The saltatorial orthopteroid insects did not originate in North America. Five avenues of entry were utilized in migration from other parts of the world. These were: (1) ancestral forms migrated to this region in Pangaean times when all continents formed a single land mass; (2) later in time, taxa migrated from Europe when Eurasia and North America were still joined, or later via an Atlantic land bridge; (3) ancestral forms migrated northward from the Neotropical region before the separation of the two continents or, much later, when the two continents became rejoined; (4) later arriving taxa entered North America during the Pleistocene via a Beringian land bridge; (5) some species are very recent immigrants, either because of the activities of man or by migration into Canadian territory from the south.

The fossil record is very incomplete. It indicates past climatic conditions, but is of limited assistance concerning extant taxa.

Pleistocene glaciation had a profound effect upon the distribution of extant species. Many species were forced to move southward to escape the advancing ice. Some species probably were eliminated. It is clear that most of the extant species have migrated northward since the recession of the Wisconsin glacier.

The Bruce spanworrn, Operophtera bruceata (Hulst), is most common in the mid latitudes of the North American Continent; in Canada it occurs from Newfoundland to the interior of British Columbia (Prentice, In Press) and has been reported from Vermont and Wisconsin in the United States (Craighead, 1950.) Three outbreaks of this insect have been recorded in Alberta. The first occurred in 1903 (de Gryse, 1925) and was apparently of short duration. The second reported by Wolley Dod (1913) occurred in 1913 and denuded hundreds of acres of aspen poplar. Heavy defoliation in the third outbreak became evident in 1957 (Brown, 1957) but an examination of Forest Insect Survey records revealed that population buildup began about 1951. The outbreak continued to expand until 1958 and began to decline in 1959; by 1961 populations were again low except for one or two isolated areas where moderate to low populations persisted. At the peak of the outbreak in 1958 approximately 50,000 square miies were moderately or heavily infested and many more lightly infested.

The effects of various levels of infestation of the corn leaf aphid, Rhopalosiphum maidis (Fitch), on yield of field corn were examined from 1965 to 1970 inclusive when all plants whose yield might have been influenced by factors other than aphid feeding were excluded from the data. A possible relationship between moisture stress in plants and degree of aphid injury was also investigated.

A light infestation (maximum of 400 aphids on the tassel) caused average yield reductions up to 8.3% when plants were under moisture stress, but nil to negligible losses when moisture was adequate. Moderate infestations (many hundreds of aphids on part of the tassel) produced average losses up to 34.8% under drought conditions and up to 11.8% when moisture was abundant. Severe infestations (many hundreds of aphids on most of the tassel) caused average yield reductions ranging from 43.2 to 91.8% when plants were under water stress and up to 58.9% even with abundant moisture. Very severely infested plants (many hundreds on all of the tassel and whorl leaves) were usually barren or had ears with just a few kernels regardless of moisture conditions.

Most injury from aphid feeding appeared to occur before and during pollination. No particular combination of temperature and rainfall favored aphid buildup.

First instars of 93 North American species of mosquitoes are studied and 56 are illustrated, 41 for the first time. Generic differences are well marked in this instar and nearly all species are separable.

Two keys to the 11 North American genera are presented; the first is constructed to show similarities between first and later instars. Each genus is described and keyed to species, and notes are given on each species. A supplementary key to the species of the southeastern states is designed for the use of a binocular microscope with magnification up to 60 ×.

Specific and generic differences are as well marked in the first as in the fourth instar. Identifications are as easy or as difficult in the first as in the fourth instar, though usually based on different characters.

An expanded key to the North American species of Aedes, incorporating those previously treated by Bohart and by Price, is attempted. The key reveals several species complexes which have not been discerned from other stages of the life cycle, namely, Aedes canadensis, nigromaculis, punctor, stimulans infirmatus and trivittatus.

A key to the first instars of the 37 species of the world-wide Anophelinae is presented, on the basis of published descriptions and figures of the exotic species.

An olfactometer is described in which an attractive zone is established and maintained in a precisely determined location on the floor (or wall) of an observation chamber and also in the air adjacent to it. Insects must therefore manifest their normal behavior in finding their way to it. The attenuation of the attraction by "background odors" can be studied quantitatively.

The eggs of a queen bumblebee are undeveloped when the queen emerges in the spring from winter hibernation. After emergence, the eggs develop while the queen is feeding on available sources of nectar and pollen. It is generally assumed that physiological changes associated with egg development stimulate a queen to search for a nesting place and start a colony. However, there is little information available on the relationship between egg development and the colony-founding behavior of the bumblebee.

Podisus sagitta (Fab.) is a small- to medium-sized predatory stink bug, which is distributed from the southern United States into South America. The immature stages and both sexes of the adult insect from a laboratory strain are described and illustrated. Notes on the life history of P. sagitta also are given.

Dryness of either an insect's habitat or its food has often been reported as inducing diapause. This has been well substantiated in Pectinophora (8, 21, 22) and Loxostege (23). Also, a difference in body moisture between forms of the same species, in diapause and not in diapause, has been recorded in Leptinotarsa (9), Lucilia (11), and Carpocapsa (24), there being less water in the insects in diapause. It is significant, though, that in preparing for diapause Leptinotarsa achieves a reduction in moisture content, even when there is an abundance of water outside, by excretion (4).

We examine the implications for intercontinental dispersal of the extinct ant genus, Titanomyrma Archibald et al. (Hymenoptera: Formicidae: Formiciinae), following the discovery of its first fossil in Eocene temperate upland Canada. Modern Holarctic distributions of plants and animals were in part formed by dispersals across Late Cretaceous through early Eocene Arctic land bridges. Mild winters in a microthermal Arctic would allow taxa today restricted to the tropics by cold intolerance to cross, with episodic hyperthermal events allowing tropical taxa requiring hot climates to cross. Modern ants with the largest queens inhabit low latitudes of high temperature and mild coldest months, whereas those with smaller queens inhabit a wide variety of latitudes and climates. Gigantic and smaller formiciine ants (Titanomyrma and Formicium Westwood) are known from Europe and North America in the Eocene. The new Canadian Titanomyrma inhabited a cooler upland. It is incomplete, indistinctly preserved, and distorted in fossilisation, and so we do not assign it to a species or erect a new one for it. The true size of this fossil is unclear by this distortion: small size would support gigantism in Titanomyrma requiring hot climates and dispersal during hyperthermals; if it was large, it may have been cold-winter intolerant and able to have crossed during any time when the land bridge was present.

Ips calligraphus (Germar), I. ponderosae Swaine and I. interstitialis (Eichhoff) represent one variable species with the oldest name, Ips calligraphus (Germar) taking precedence. Ips calligraphus can always be recognized by the six spines on each side of the declivity. All other species in North America have less than six spines on each side.

A model for intraspecific competition that incorporates the effects of inter- and intra-stage survival rates, spatial distribution, and variation in growth is developed using basic probability theory. Simulation results for cannibalism in Heliothis zea (Boddie) are presented and intraspecific competition is shown to have effects on population cyclicity and on mortality.

Under laboratory and field conditions in Ontario, Canada, we explored the natural history of Phasgonophora sulcata Westwood (Hymenoptera: Chalcididae), an indigenous solitary endoparasitoid of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in North America. Adult P. sulcata emergence was ~20.2–23.9 days after host emergence at 21°C, with P. sulcata females emerging an ~5.4–5.8 days before males. Females also represented 61.8 and 67.0% of emerging adults in the two years sampled. Mean adult longevities for males and females of P. sulcata were 23.8±1.10 and 28.9±1.11 days at 21°C, respectively. Mean potential fecundity of P. sulcata at emergence was 55.7±2.9 eggs per female. Based on adult emergence, parasitism at two sites varied from 11.7% to 34.4%. Adult parasitoids were first observed in the field in early June, with peak capture occurring in late June. Parasitism rates in A. planipennis-infested ash trees was not affected by tree height below 360 cm, whereas parasitism was not observed at heights>360 cm. Our results suggest that although mass rearing will be challenging, observed parasitism rates in conjunction with temporal and spatial synchrony indicate that indigenous P. sulcata may be an important source of mortality for A. planipennis populations.

Ce texte décrit deux nouvelles fourmis néarctiques appartenant au genre Leptothorax (stricto sensu). La première, L. retractus, occupe un territoire transcontinental, tandis que la deuxième, L. sphagnicolus, fut repérée jusqu’à présent uniquement dans les pessières tourbeuses de la région du Saguenay–Lac St Jean, au Québec. Leur nombre respectif de chromosomes se chiffre à n = 17–18 et n = 13. Toutes deux se distinguent par une production inusitée de formes femelles intermédiaires et une répartition géographique de nature boréo-tempérée. Leurs caractéristiques bio-écologiques connues et leurs relations taxonomiques dans le genre sont discutées.

Counts of the cabbage maggot, Hylemya brassicae (Bouché), on cabbage did not conform to the Poisson distribution, there being an excess of uninfested and highly infested plants over the expected number. But when the negative binomial series was fitted to the observed distribution, the discrepancies were not significant when tested by chi-square. The negative binomial parameter k tended to increase with density. Using a common k, the distribution of the various stages may be described by expansion of (q − p)−k, when values of k are as follows: egg 0.78, larva 0.71, pupa 0.84. Three different transformations are offered for stabilizing the variance of field counts.

Four indigenous parasites of R. buoliana are discussed: Exeristes comstockii (Cress.), Scambus hispae (Harr.), Scambus tecumseh Vier. and Itoplectis conquisitor (Say). The first three are external larval parasites and the fourth an internal pupal parasite. Observations are given on the hosts, life histories, and habits under laboratory conditions. The immature stages are described.

Rearing of Diabrotica balteata LeConte is possible throughout the year at temperatures between 10° and 30 °C. Adults feed on a very large variety of host plants. Good edibility combined with pronounced oviposition and egg viability are found in Cucurbitaceae, Leguminosae, Rosaceae, and Cruciferae. However, cases of good edibility with no oviposition are also established in several families. Optimal adult longevity lies between 17° and 24 °C and oviposition indicates two high peaks within the female life span.Temperatures below 0 °C are detrimental to all stages and those between 0° and 4 °C mainly to larval and pupal stages. No diapause is found in any stage and this explains the limited distribution within warmer regions of the Americas. Precautions not to introduce this species into other continents should be taken.