The parasite and predator component of within-tree southern pine beetle, Dendroctonus frontalis Zimmermann, mortality was investigated by mechanically excluding insect parasites and predators from the bark surface of naturally infested shortleaf, Pinus echinata Mill., and loblolly, P. taeda L., pines. Mortality caused by insect parasites and predators was determined by comparisons of five treatments that differed only in the duration of natural enemy exclusion. These natural enemies were responsible for 28.04% and 23.85% of the within-tree beetle mortality in 1978 in Arkansas and in 1979 in Georgia, respectively. Natural enemy species that arrived on the tree during the first week following mass attack by beetles caused the greatest amount of mortality.

Predator density was greater than parasite density at both locations. The majority of the predator complex arrived during the first week following mass attack by beetles, while the parasite complex arrived throughout the entire period of beetle brood development.

A linear response was found between the number of southern pine beetle prey and the number of prey destroyed per predator. A mean (± S.E.) of 4.79 ± 0.64 southern pine beetle immatures were destroyed by each individual predator.

The threshold temperature of development, life table, and innate capacity for increase of the twospotted spider mite, Tetranychus urticae Koch, were established from life stage development studies at constant temperatures. The threshold for development was determined to be 10.0°C. The durations in degree-days above 10°C from the beginning of the egg stage to adult for females were 141.3, 152.3, and 139.8; for males 134.2, 144.7, and 135.2 at 15°, 18°, and 21°C, respectively. Life tables were constructed and innate capacity for increase was .069, .156, and .372; net reproduction rate 20.8, 38.4, and 58.1; and mean generation time 44.0, 23.4, and 10.9 at 15°, 18°, and 21°C, respectively.

Populations of the citrus red mite, Panonychus citri (McGregor), reared on “rough lemon” seedlings (Citrus limon (L.) Burm.) in a greenhouse and treated with malathion or permethrin were significantly higher than those on untreated seedlings. Significant increases were demonstrated in age-specific fecundity (mx), mortality corrected mx (lx mx), and net reproductive rate (Ro) values for mites reared in the laboratory on leaves treated with malathion or permethrin when compared with those reared on untreated leaves. Mites reared on oxamyl-treated leaves exhibited significant reductions in age-specific survivorship (% lx), mx, lxmx, and Ro values compared with those reared on untreated leaves. The importance of reproductive stimulation in relation to other causes of pest resurgence is discussed.

The importance of predators in the natural control of mosquitoes has been suggested by a number of workers. Comprehensive reviews have been presented by Hinman (1934) and Gerberich (1946). The conclusions are open to some question, however, since the investigations were confined for the most part to studies in laboratory aquaria. These environments create conditions such as crowding, absence of prey shelter, and lack of alternative prey, which prevent an analysis of predation in terms of field conditions. An accurate assessment of predation in nature requires a technique to identify predators that have consumed prey. This is a report on an attempt to analyse the predator-prey relationships of animals in a natural mosquito pool in a woodland swamp near Chatterton, in Hastings County, Ontario, in April and May, 1953, by means of a radioactive tracer.

Parasitism by Aphidius smithi reduced the fecundity and population growth of pea aphid, Acyrthosiphon pisum. Aphids that were parasitized during the first or second instar period died as fourth instars without producing offspring. Parasitized third or fourth instars usually reached maturity and produced a variable number of progeny. Parasitized adult aphids stopped producing nymphs approximately 7 to 8 days following attack by A. smithi. Equations are given for the relationship between the mean total fecundity, the intrinsic rate of increase, and the doubling time of apterous and alate viviparous pea aphid and the aphid age at the beginning of parasitism.

The tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous crops. The characterisation of its host range could help to understand and prevent the dispersion behaviour of the insect in the environment. In this study, the ability of T. absoluta to develop on 12 cultivated or non-cultivated plants including Solanaceae, Amaranthaceae, Convolvulaceae, Fabaceae, and Malvaceae species under laboratory conditions was assessed. For each plant species, we monitored the development times of immature stages, survival, sex ratios, and adult fecundity rates. All the six tested non-solanaceous plants, including Chenopodium Linnaeus (Amaranthaceae), Convolvulus Linnaeus (Convolvulaceae), and Malva Linnaeus (Malvaceae) species, were not able to sustain (i.e., allow growth and development) T. absoluta larvae. Solanum Linnaeus (Solanaceae) species were the most suitable host plants for the pest, but others could be opportunistically colonised with fewer incidences. Tuta absoluta appears to be strongly related to solanaceous plants that would predominantly support self-sustaining field populations. Preventing crop infestation by removing potential host plants in the immediate field vicinity and culture rotations with non-solanaceous crops is of primary importance.

In 1958, intensive studies on the population dynamics of the diamondback moth, Plutella maculipennis (Curt.), on cabbage were initiated in long-term study plots at Merivale, Ontario. The object was to construct ecological life tables (Morris and Miller, 1954) for successive generations of the insect, and, ultimately, to develop a mathematical model describing survival of field populations. This paper reports on the variation between samples of immature stages of the moth, and between some of the mortality factors affecting its abundance, and on the use of these data in designing a sampling plan with acceptable limits of precision.

Results of a 2-year survey in Alberta, Canada, identified a parasitoid fauna of filth flies distinct from that generally reported for cattle confinements in the United States. Twenty-two feedlots were surveyed using freeze-killed sentinel house fly pupae. Parasitism averaged 0.25%. Ten species of hymenopterous parasitoids were recovered. As a percentage of the total number of pupae parasitized, these species were Muscidifurax raptor Girault & Saunders (37.4%), Trichomalopsis sarcophagae Gahan (23.9%), Urolepis rufipes (Ashmead) (18.5%), Muscidifurax zaraptor Kogan & Legner (6.9%), Nasonia vitripennis Walker (6.5%), Trichomalopsis sp. (3.7%) (Pteromalidae), Phygadeuon sp. (2.9%) (Ichneumonidae), Dibrachys cavus (Walker) (0.1%) (Pteromalidae), Synacra sp. (0.1%) (Diapriidae), and an unidentified Braconidae (0.1%). No differences were detected among natural regions of the province. Three categories of seasonal activity are identified which expand on previous groupings of species by their geographic distributions. The abundance of T. sarcophagae and rarity of species of Spalangia Latreille, 1805 are in marked contrast to results of surveys conducted in the United States. This difference suggests that species used to manage populations of pestiferous flies associated with livestock in the United States could be inappropriate for use in Canada.

The scale insect Toumeyella numismaticum Pettit and McDaniel occurred in small areas of heavy infestation in jack pine, Pinus banksiana Lamb., stands of southeastern Manitoba, where it was present in the same areas every year. The large populations of Formica obscuripes Forel present in the scale-infested areas lessened the effectiveness of the main predator of the scale, the coccinellid Hyperaspis congressis Watson, through interference with the Hyperaspis adults.

Deposits of the nuclear-polyhedrosis virus of Trichoplusia ni (Hübner) and of the granulosis virus of Pieris rapae (Linnaeus) were largely inactivated within 10 days after sprays were applied to field plots. Deposits on plants retained in a growth room or in a greenhouse were inactivated but more slowly than those exposed to direct sunlight. Deposits on plants kept in the dark lost little activity indicating that exposure to light was responsible for inactivation.

Activity of deposits of the viruses was extended substantially by addition of protectant materials to the sprays. The addition of charcoal mixed with skim milk powder, egg albumen, or brewer’s yeast resulted in a 3-fold increase in the period over which an LD50 of virus was maintained on the plants.

Discrepancies in the degree of biological control of insect pests where the food plant species of the host were the only known variants in the environment have been subjects of scattered observations in the literature by Morgan (1910), Compere (1936), Gilmore (I938), and others.

A long period of speculation on the existence of strains of California red scale, Aonidiella aurantii (Mask.) immune to attack by parasites culminated in the discovery by Flanders (1939a, 1942a) that the hymenopterous parasite Habrolepis rouxi comp. reproduced satisfactorily on A. aurantii on Citrus spp. but that verv few emerged from the same species of scale on sago palm, Cycas revoluta Thunb. This was considered to be the reason for Compere's early failure to bring the hymenopterous parasite, Comperiella bifasciata How, from the Orient to California on scale-infested sago palm; Smith (1942) concluded: “Recognition must be given to the possibility that the host plant may confer on the host insect a kind of immunity to parasitization”.

Development of eggs of 35 species of Nearctic and Palearctic Pentatomoidea are described. Eggs are discussed in relation to the number of ovarioles of each species, characteristics of eggs, incubation time, diapause, embryonic development, embryonic orientation, hatch, and parasitism, and are classified into two groups in relation to then-form, position of egg-burster, and hatch. Emergence of first-instar larvae is described in representatives of five families.

The average rate of diet uptake by the 1st–3rd instar nymphs of the pea aphid, Acyrthosiphon pisum (Harris), on chemically defined diets containing 0.0–5.0% amino acids varied from 0.08 to 0.23 μl/aphid/24 h and that by 4th instar nymphs to adults varied from 0.15 to 0.74 μl/aphid/24 h. The presence of amino acids increased the acceptability of diets to a great extent, as uptake on such diets was 2–5 times more than that on amino acid free diets. Uptake was lowest on diets lacking amino acids, and highest on those containing 3.5 and 2.5% amino acids by 1st–3rd instar nymphs and 4th instar nymphs to adults respectively. It is suggested that certain amino acids, either alone or in combination, act synergistically with sucrose as phagostimulants. Methionine was slightly phagostimulatory to the pea aphid and enhanced the acceptability of a free amino acid diet and of a sucrose solution.

As expected the rate of feeding increased as the aphids grew. Nymphs reached the adult stage, and reproduced on each diet, except on the one lacking amino acids. The longevity on different diets varied from 7 to 37 days. A concentration of 2–4% amino acids, with an optimum at 3.5%, appears to be essential for the growth, survival, and larviposition of the pea aphid.

Due to the punctures made in the stretched parafilm by aphids during feeding the rate of evaporation from fed sachets was significantly higher than that from unfed sachets. It is therefore suggested that in experiments where rates of feeding are measured by differential weighings of the sachets, these be renewed at 24-h intervals.

Twig beetles in the genus Pityophthorus Eichhoff are known to be associated with the pitch canker pathogen, Fusarium circinatum, in California. Phoresy of the pathogen on these species has been reported to occur when insects emerge from diseased branches and when they infest disease-free, cut branch tips. To demonstrate that twig beetles can vector the pathogen, studies of phoresy and transmission were conducted in a native Monterey pine, Pinus radiata D. Don (Pinaceae), forest. Phoresy was confirmed for both Pityophthorus setosus Blackman and Pityophthorus carmeli Swaine, and P. setosus was shown to vector the pitch canker pathogen when contaminated with fungal spores and caged onto Monterey pine branches. When attractive baits were used to increase visitation to Monterey pines by P. setosus, baited trees were more likely to develop pitch canker than unbaited trees even though the beetles did not tunnel into the host to develop egg galleries. Therefore, twig beetles are competent as vectors of the pitch canker pathogen, and their vectoring activity, though requiring a wound, does not require that they establish egg galleries in the host.

The heat requirements for diapause termination in pupae of Hyphantria cunea are subject to a high degree of generic control. Offspring–parent regression analysis based on a positively assortative mating pattern, which is the normal pattern in field populations of this species, provides a slope of 0.60. Positive skewness in the distribution of heat requirements can be reduced by conversion to logarithms. The inheritance of heat requirements is sex-linked, with the female being the heterogametic sex. Fitness characters that are significantly correlated with heat requirements affect larval and pupal survival rates and the weight of both male and female pupae. When the effects of these correlated survival rates are removed mathematically, the slope of the offspring–parent regression is increased to 0.80.Changes in the heat requirements of natural populations, in relation to the amount of heat available each year, influence their survival rates. The comparison of actual and calculated changes, based on models for heritability and selection pressures, will be the subject of a later paper in this series on H. cunea.

The effect of temperature on the age-specific fecundity and the survival of apterous and alate virginoparous pea aphid, Acyrthosiphon pisum (Harris), from Kamloops, B.C., was measured. Demographic statistics were estimated for 10.3°, 14.8°, 19.7°, 26.1°, and 27.8°C constant and for fluctuating field temperatures. On a 24-h-day time-scale, temperature and longevity were inversely related in both morphs; total fecundity was highest at average and low constant temperatures. On a physiological time-scale, the intrinsic rate of increase (rm) was insensitive to changes in constant temperature in the range between 10° and 20°C; temperatures above 25°C were detrimental to aphid population growth and survival. Alate virginoparae generally had a longer pre-reproductive period and achieved a lower mean total fecundity than apterae maintained under identical conditions. The usefulness of laboratory measurements for the prediction of population growth under variable field temperatures is discussed. Differences in the reproductive patterns of alate and apterous pea aphids are considered in the context of the r- and K-hypothesis of selection.

Hunger and abundance of adult Coccinella californica (Mannerheirn) preying on pea aphids, Acyrthosiphon pisum (Harris), on alfalfa, Medicago sativa L., were assessed in the field. There was no consistent relationship between abundance or hunger and aphid density. The field beetles encountered in sampling were 4 times hungrier at each observed aphid density than expected from a simulation model of the predation that is driven by hunger. Laboratory studies revealed a circadian rhythm of beetle activity that was modified by hunger. An index of predatory potential (number of beetles times average hunger) was found to be a better indicator of impact of the beetles than absolute numbers of all coccinellids or hunger separately. It is suggested that the beetles encountered in simply walking through a field produce the most useful index of numbers of hungry beetles. This census must be done daily however because of the high vagility of adult coccinellids.

Relationships between mean egg weight and overwintering survival in the laboratory were explored in selected large- and small-egg lines and also in first laboratory generations from 5 widely separated locations. Overwintering stress was provided by prolonged storage or above average storage temperature. Under stress large eggs were shown to have greater survival than small eggs in both stocks of insects. The results explain why spruce budworm from higher latitudes (longer winters) have heavier (larger) eggs. Other effects of prolonged storage and storage selection on subsequent size and development rates in both the treatment and the F1 generations are reported.

On the basis of the relative size of the spermatophore sac the subfamily Gryllinae is separated into two tribes, Gymnogryllini and Gryllini, this structure being small in the former and very large in the latter. Each tribe is further divided into two subtribes on the basis of consistent differences in the shape of the epiphallus. Six new genera are added.

The presence of styli on the epiphallus of species of Turanogryllus Tarbinski is suggested as evidence for the origin of the male genitalia from the segmental appendages. Possible homologies of the structures of the male genitalia of Grylloidea and Acridoidea are suggested.

Unlike most other arrhenotokous species, D. fuliginosus females cannot control fertilization of their eggs and in an optimal environment the sex ratio of any one strain is constant. Variations in the sex ratio occurred when unfavourable environmental conditions prevailed before, during and immediately following mating. Beyond half their life span, males inseminated less than half the females they mated and the inseminated females produced fewer female progeny. Temperatures above 27 °C. during post-embryonic development sterilized otherwise functional males but had much less effect on females. Structural defects of either sex were rare. Mating was successful only within the normal range for optimal adult activity. Although females were inseminated by more than one male, the sex ratio of their progeny was not affected. Larval mortality from superparasitism above 65 larvae per host differentially favoured survival of males, heightening the incidence of pairing in nature at low host population densities. The percentage females was significantly reduced when oviposition was interrupted, or delayed by low temperature, providing a possible explanation for the numerous reported differences in the sex ratio between laboratory and different geographically located populations.