To evaluate sociality in small carpenter bees (Ceratina Latreille), we studied the life history and nesting biology of a common eastern North American species, Ceratina (Zadontomerus) calcarata Robertson. Pan-trap and nest collections throughout the active season (May to September 2006) were used to assess C. calcarata’s seasonal phenology and nesting biology in southern Ontario. Adults overwintered in their natal nests. Males emerged in early May and occupied preexisting hollows in twigs and stems. Females emerged from hibernacula 2 weeks later, founding new nests. Nest founding and provisioning occurred throughout the spring; females remained with developing brood through the summer. Complete nests contained, on average, 6.9 offspring, with egg-to-adult development averaging 46 days. Ceratina calcarata is subsocial rather than solitary: mothers are long-lived and nest-loyal, and care for offspring from egg to adulthood. Subsociality is found in all behaviourally classified small carpenter bees, while some species cross the boundary into social life, making Ceratina an important genus for the study of the transition between solitary and social life.

A highly sensitive bioassay of the olfactory response of I. confusus is described. The response of beetles to air streams carrying attractants is a chemoklinotaxis but positive orientation occurs only in moving air. There is no evidence of ameno-taxis in odorless air streams or orientation to attractants in still air. Male behavior is characterized by an “area” orientation near the attractive material, an indirect approach to the source as shown by their entering adjacent air channels, and stopping frequently in the traverse during which they make klinotactic movements. The females exhibit a “point” or “straight-line” response, crawling directly to the source, rarely deviating into adjacent channels and only occasionally interrupting their approach.

Bark-wood samples of ponderosa pine become attractive 4-6 hours after male beetles are introduced into preformed entrance tunnels, the peak attraction occurring between 18 and 144 hours. Frass is not attractive until 9-12 hours after introduction of males. The ratio of females to males responding positively during the peak attraction period was approximately 8:5. The level of attractiveness to females falls as the season progresses, the highest response being recorded in late May and June. Sexual maturity as judged by the appearance of motile sperm was not correlated with host feeding or the initiation of attraction. Frass of males boring in Douglas fir was unattractive to females.

Attraction is initiated by male feeding in the phloem-cambial tissue of a host and is delayed until the first food has passed through the gut. The attractant appears to be associated with male excrement and may be produced, at least in part, in the hindgut.

The results of systematically conducted field observations revealed that the site of male:female assembly for mating in apple maggot flies, Rhagoletis pomonella (Walsh), was exclusively on the fruit of the larval host plant. Laboratory observations were in strong agreement with this finding.

The "pars stridens–plectrum" terminology of stridulatory organs is discussed. A list of 77 species of Scolytidae known or presumed to bear stridulatory structures is presented. The three types of scolytid stridulatory organs, vertex–pronotal, gula–prosternal, and elytra–abdominal tergites, are described and discussed.All North American species in the genus Ips were examined for stridulatory organs. The gula–prosternal type was found on females, and possibly males, of I. concinnus (Mannerheim) and I. mexicanus (Hopkins). The vertex–pronotal type occurs on females of 14 other species. No stridulatory structures were found on either sex of the remaining 17 Ips species. Females of 15 of the 18 pine-infesting species have stridulatory organs, while 14 of the 15 spruce-infesting species apparently lack them. Female I. confusus (LeConte) stridulate when entering the male entrance tunnels. Removal of the stridulatory organ has two effects: males do not permit some of these non-stridulating females to enter, and they deny entry to others for an unusually long period of time.Possession of a stridulatory apparatus in the Scolytidae appears to be associated with the sex opposite to that which initiates the entrance tunnel.No significant differences were found between gallery systems constructed by female I. confusus with the stridulatory organ removed and those constructed by stridulating females except that more single stridulating females excavated two or more egg galleries from a nuptial chamber.

Synchrony of insect and host tree phenologies has often been suggested as an important factor influencing the susceptibility of white spruce, Picea glauca (Moench) Voss, and other hosts to the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae). We evaluated this hypothesis by caging several cohorts of spruce budworm larvae on three white spruce populations at different phenological stages of the host trees, and then comparing budworm performance with host phenology and variation of 13 foliar traits. The beginning of the phenological window of susceptibility in white spruce occurs several weeks prior to budbreak, and the end of the window is sharply defined by the end of shoot growth. Performance was high for the earliest budworm cohorts that we tested. These larvae began feeding 3–4 weeks prior to budbreak and completed their larval development prior to the end of shoot elongation. Optimal synchrony occurred when emergence preceded budbreak by about 2 weeks. Larval survival was greater than 60% for individuals starting development 1–3 weeks prior to budbreak, but decreased to less than 10% for those starting development 2 or more weeks after budbreak and thus completing development after shoot elongation ceased. High performance by the budworm was most strongly correlated with high levels of foliar nitrogen, phosphorous, potassium, copper, sugars, and water and low levels of foliar calcium, phenolics, and toughness. These results suggest that advancing the usual phenological window of white spruce (i.e. advancing budbreak prior to larval emergence) or retarding budworm phenology can have a large negative effect on the spruce budworm’s population dynamics.

Several aspects of overwintering were studied in the larvae of selected species of chironomids living in shallow ponds.In two species (Einfeldia synchrona Oliver and Polypedilum simulons (Townes)) from a pond near Ottawa, Ont. (45° N.), development ceased in mid-November and the gut was subsequently evacuated. A species of Chironomus from another pond did not evacuate the gut although feeding ceased. In the laboratory, larval development of Einfeldia collected at any time of year continued except at low temperatures, but pupation occurred only at long day-lengths. Seasonal changes in horizontal distribution were apparently not primarily related to possible winter effects, but to water depth changes. Larvae of E. synchrona penetrated deeper mud layers during winter (as well as in midsummer); those of P. simulans were always confined to superficial mud layers.The later instars, at least in Chironomini, usually predominated during the winter, but season to season variation was marked. In the arctic all instars except the first were present. Closed winter cocoons were found in several temperate and arctic species. Some were made by sealing an existing tube, others by building a more or less transparent tightly applied cocoon. Inside these cocoons, the larvae were tightly folded in different ways more or less characteristic of the species. At Ottawa, cocoons were usually formed well after ice cover, and partly in response to low temperatures. Larvae showed a lower water content in winter than in summer. In the arctic, larvae were also somewhat dehydrated in winter, but there was in addition a different type of dehydration which resulted in shrivelling.There was no significant ability to resist freezing by inoculation with ice. Freezing tolerance was found in some temperate and all arctic larvae and was temperature- and time-dependent. In temperate areas, freezing-tolerant larvae were nevertheless freezing-susceptible in summer.These studies and previous findings are discussed in relation to winter habitat conditions and the remainder of the life-cycle. Generalizations are compromised by complex inter- and intra-species differences and by habitat variations. Freezing tolerance is widely distributed through the genera of most subfamilies except the Tanypodinae, and is probably most general in the Orthocladiinae. Since there are few specializations of larval physiology which explain such tolerance, the Chironomidae can probably be considered as largely pre-adapted to a rigorous winter environment.

It is generally agreed that insects whose larvae feed on plants do not increase to the larval food limit except in sporadic and unusual cases. In the few detailed studies which have been made, as, for example, Varley's (1947) study of the knapweed gallfly, the evidence suggests that the insects are held in check by parasites and predators. Andrewartha and Birch (1954) are of the opinion that shortage of food is probably the least important factor in limiting the numbers of animals in a natural population. On the other hand, they have pointed out (p. 489) that while it is unusual for an extensive population to consume all or most of the stock of food in its area, it does not follow that the amount of food is rarely of major importance in determining the numbers of a natural population. Several examples (p. 492) were given in which shortage of food was chiefly responsible for failure of population increase even though the absolute supply seemed adequate. In these cases local supplies were exhausted and the chance of finding fresh supplies depended upon the distribution and abundance of food and the powers of dispersal of the animals. In other words, the food was inaccessible relative to the animals' capacities for dispersal and searching.

Population ecology requires realistic and precise analyses of whole systems, or processes, and not just fragments of them. This poses some difficult problems because of the distinctive complexity of these processes. Recent studies of predation have shown, however, that it is possible to achieve great analytical depth and to simulate whole systems in the form of realistic and precise mathematical models. This is accomplished by ignoring the degree of simplicity traditionally required of population models and by emphasizing the need for reality. Extensive experimentation is required to suggest and test possible explanations for the action of each component of the process so that the explanation evolves in gradual steps to include one component after another. The form of the explanation and the resulting equations is hence dictated by the process itself and not by the need for mathematical neatness. The considerable complexity of the predation model arose from features common to many biological processes i.e. the prevalence of limits and thresholds, the presence of important discontinuities and the historical character of biological events. These features can be analyzed effectively only by establishing an intimate feed-back between experiment and theory. Mathematical models incorporating these features are admirably solved using digital computers. Computers, and the languages used to program them, seem to be ideally suited to handle the distinctive type of complexity shown by population processes.

At the Vancouver laboratory a large number of cages were needed to confine aphids to single leaves in virus transmission experiments. The cages had to be of simple construction, light, and easily manipulared. The cage developed was similar to that of MacGillivray and Anderson (1957), but was simpler to make, and the materials were easily obtained locally. The materials are: acrylic plastic tubing, metal hair-curl clips, foam rubber, corks to fit the tubing, and muslin.

Calling (extrusion of the sex pheromone-producing gland) by spruce budworm females follows a circadian rhythm regulated by the initiation of the photophase. At 2 °C 50% of the females call by 131/2 hr after "lights-on." Calling starts earlier at cooler temperatures. Females that have not been exposed to lights-on start calling as soon as darkness occurs. Virgin females are most attractive 3 to 4 days after emergence. Mated females call intermittently and are attractive but compete poorly with virgins. Once started, female budworm call continuously throughout the calling period, implying that their pheromone release rate is lower than if they called for short intervals only as in some other Lepidoptera. This may influence the quantities of synthetic pheromone required to disrupt mating behaviour. Calling behaviour is not influenced by the proximity of other adult budworm. At high population densities, males are apparently able to locate females before or as soon as they start to call, suggesting that communication is short range. Longer distance communication probably operates at low population densities. Population regulation by disrupting mating behaviour is therefore unlikely to succeed except at relatively low population densities.

The amount of dead wood in forests has decreased owing to modern forest practices, and many species associated with this habitat are currently threatened. In Sweden during the last decade, naturally downed logs have been retained and, at clearcuts, high stumps have been artificially created to maintain saproxylic (dead wood dependent) insects. We tested how much these types of dead wood are used by sampling saproxylic beetles in dead wood of Norway spruce (Picea abies (L.) Karst.; Pinaceae) in managed forests in central Sweden. To analyse how surveys should be conducted in these kinds of studies, we compared three methods over an entire growing season. We found that the relationship between the type of dead wood and species richness was statistically significant when we used bark sieving and emergence traps, but not when we used window traps. It is impossible to ascertain whether beetles collected with window traps are related to the type of dead wood on which they are found and, therefore, such traps are less useful in studies of specific substrates. The yield from sieving was highest in spring and autumn, whereas species richness in window trap samples peaked in June and July and that in emergence traps peaked from May to July. With emergence traps we collected, on average, about twice the number of species over the whole season as we did by sieving on a single occasion in the spring. Both emergence trapping and sieving reveal what is present in individual pieces of dead wood, but these methods sample partly different faunas. We found fewer species on artificially created high stumps (on clearcuts); however, these stumps seem to be useful for some red-listed species.

The different types of individuals among the progeny of the western tent caterpillar, Malacosoma pluviale (Dyar), are concentrated in different parts of the egg mass. The most agile progeny come from some of the first eggs laid, and the least viable are among the last deposited. There is evidence that this serial arrangement stems from unequal partitioning of the maternal food reserves during egg production: a relationship similar to that recently demonstrated in the spruce budworm by I. M. Campbell. In M. pluviale, however, there also is evidence that the differences in feeding rate and food capacity displayed by the different types of females during their own larval stage affect the proportions of the various types of progeny per egg mass as well as the viability of consecutive groups of eggs within the mass. Although these maternal influences are not heritable in the usual genetic sense, they are clearly transmissible between generations. And field studies have shown that their more adverse consequences for local populations are cumulative and ultimately lethal.

We studied the effects of agricultural practice on ground beetles, using pitfall traps in field plots and in an uncultivated meadow near Edmonton, Alberta. Ground beetle abundance and species richness were higher in plots operated under an organic farming regime than in those under a chemical regime, but neither crop type [barley (Hordeum vulgare L.), faba bean (Vicia faba L.), barley-pea (Pisum sativum L.) intercrop] nor crop rotation had an effect. Reduced tillage did not significantly change overall carabid activity or species richness but species differed in their response to tillage treatments. The carabid assemblage from an uncultivated field differed conspicuously from assemblages in the crops and fescue. Carabid abundance was highest in the meadow and the fauna was dominated by the exotic species Pterostichus melanarius Illiger. Effects of agronomic practice on carabid assemblages are complex, reflecting the interaction of biological traits of particular species and the combination of agronomic treatments applied.

The accumulation of monoterpenes during the defensive response by grand fir was quantified over a 28-day period. Monoterpene content increased exponentially with time and varied greatly among trees. Following analysis, sampled trees were observed for 4 years. Those trees which showed an extensive accumulation of monoterpenes in response to artificial inoculation with fungi transmitted by the fir engraver were less likely to be killed during this period than trees which exhibited low levels of secondary monoterpene accumulation. The extent of the defensive response was influenced by host age, disease, crown class, and artificial stress. Following inoculation with fungi transmitted by the fir engraver, the proportions of limonene, myrcene, and Δ-3-carene, present in the monoterpene fraction increased. In previously reported laboratory bioassays, each of these compounds has demonstrated higher toxic or repellent properties, or both, than have the other monoterpenes present in grand fir. Mechanical injury resulted in less pronounced reactions than did fungal inoculation. Necrotic lesion formation is accompanied by an increased concentration of short-chain hydrocarbons, followed by a decline to normal levels. Necrotic lesion formation and monoterpene synthesis represent at least two independent activities during the wound response.

Alternating temperatures resulted in higher intrinsic rates of increase (rm) than constant temperatures within the range of temperature favourable for growth and reproduction of the pea aphid. This difference was due to slightly faster development and earlier attainment of maximum fecundity at alternating temperatures.

Preliminary mathematical models relating rm to constant and alternating temperatures are derived. These are:

for constant temperatures and

for alternating temperatures of 5°, 10°, and 15° amplitudes respectively. Average deviation between empirical and computed values is 2%. The efficacy of these models is restricted to temperatures favourable for development and reproduction of the pea aphid.

Amber of Cretaceous Age from Canada is an exceptionally fine source of well-preserved fossils of a wide variety of insects and related animals. Since these fossils can yield much information about the forms of, and conditions for, life in the Cretaceous Period some 75 million years ago, they represent a highly interesting and valuable scientific resource.The history, relative abundance, nature, biological origin, and significance of Canadian amber is reviewed and related to similar aspects of European or Baltic amber. Reported occurrences of amber in Canada (about 50) are assembled and some 350 arthropod inclusions discovered in the amber collections made thus far are tabulated, with respect to their origins, classification, and present location. The article contains one map, two tables, and 16 figures.

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.

Community organization is defined as the mean number of trophic links connecting species of different trophic levels in a community. For the special purposes of this paper, competition is assumed to occur whenever two species are known to eat the same food species. Community stability is defined as the reciprocal of the mean, for all species, of the standard error of logarithms of annual collection sizes. It is thus a measure of stability over time of the species populations in a community. Several authors writing about the relationship between community organization and community stability have insisted that the stability of a complex ecological system increases with the number of avenues by which energy can flow through it. This theory does not seem consistent with the observation that some insect pest species of notorious instability are attacked by a great number of entomophagous species. In this paper we seek additional evidence bearing on the relationship between community organization and stability, using computer analysis of data collected by the Canadian Forest Insect Survey on forest Macrolepidoptera and their food plants. After considering our results, and those of other workers, we postulate the following hypothesis. Stability at any herbivore or carnivore trophic level increases with the number of competitor species at that level, decreases with the number of competitor species that feed upon it, and decreases with the proportion of the environment containing useful food. If this hypothesis is valid, too much competition in the entomophagous trophic level will not allow the species in that level to be instable enough to control an unstable pest. Therefore, the best type of biological control agent is one that has no direct competitor species. Also, the most unstable biological control agents, and hence those capable of controlling an unstable pest, will be polyphagous.

This work, designed to provide an estimate of the quantity of food consumed by spiders, was part of a more general study of the ecology of a spider population in a stand of oaks (Quercus robur L.) in Wytham Wood, Berkshire, England (Turnbull, 1960a, 1960b). Linyphia triangularis (Clerck) was selected as a test spider for the following reasons: it is a common, easily recognized, and easily acquired species; its size closely approximates the mode size of spiders in the population under observation; as far as it may be said of any spider, L. triangularis possesses few specialized features or habits; and the species is amenable to laboratory rearing and manipulation.

A reinvestigation of the sex pheromone of the eastern spruce bud worm, Choristoneura fumiferana (Clem.), showed that it contains 11-tetradecenal in the ratio 96% trans-: 4% cis-. Field trapping showed the pure trans- compound to be only slightly attractive. Maximum attraction occurred in the range 2% to 5% cis-.